Speaker 1: Welcome to the deep dive. This is where we really
Speaker 1: dig into complex topics, pull out the essentials, and basically
Speaker 1: give you a shortcut to being well informed.
Speaker 2: Yep. We sift through the information, figure out what matters most,
Speaker 2: and hopefully find some useful takeaways for you.
Speaker 1: And today we're tackling Android design patterns and best practice.
Speaker 1: We've got a great source to guide us, and the
Speaker 1: mission is pretty clear. Understand how using these patterns can
Speaker 1: help you build better Android apps.
Speaker 2: Apps that are more reliable, robust, easier to maintain, just
Speaker 2: more efficient overall.
Speaker 1: And we're going to frame this by imagining we're building
Speaker 1: an app for a small business like local sandwich delivery
Speaker 1: service exactly.
Speaker 2: It's a good way to see how these patterns actually
Speaker 2: pop up naturally during development. They're not just theory, they're
Speaker 2: practical solutions.
Speaker 1: Yeah, Understanding them gives you this vocabulary, this toolkit. It
Speaker 1: helps you spot potential problems earlier.
Speaker 2: Right, Definitely, It's like having a set of blueprints for
Speaker 2: common coding challenges makes avoiding design flaws way easier. It
Speaker 2: really accelerates lending good practice.
Speaker 1: Okay, let's start at the beginning. What exactly are design.
Speaker 2: Patterns Fundamentally, they're like proven recipes for solving common software
Speaker 2: design problems. Think of them less as specific code snippets
Speaker 2: and more as programming philosophies or strategies.
Speaker 1: And these aren't just Android things, are they not?
Speaker 2: At all? The concepts are universal. You see them across
Speaker 2: different languages and platforms. In fact, the Android SDK itself
Speaker 2: uses tons of them, Like what, well, you've got factory
Speaker 2: methods for creating objects, builder patterns for assembling complex ones.
Speaker 2: The whole listener system relies heavily on the observer pattern.
Speaker 1: They're baked right in, so it's more about grasping the
Speaker 1: idea behind the pattern than memorizing a.
Speaker 2: List Precisely, if you get the core concept, you can
Speaker 2: spot it, understand why it's used, adapt it, maybe even
Speaker 2: come up with your own variations.
Speaker 1: Okay, back to our sandwich shop. The scenario is an
Speaker 1: independent developer gets approached by this small business.
Speaker 2: Right the clients struggling with phone orders, mix ups, the
Speaker 2: usual chaos. They think a mobile app could be the answer.
Speaker 1: It's a classic setup, small business problem, potential tech solution.
Speaker 1: It gives us concrete issues that patterns can help solve.
Speaker 2: So before we even write a line of code for
Speaker 2: this samich app. We need to set up the environment first,
Speaker 2: big decision, Which Android versions to support? Ah?
Speaker 1: Yes, the API levels you've got minds DK.
Speaker 2: Version, the oldest version your app will run on. Yeah,
Speaker 2: and targets decay version, which is the version you've tested
Speaker 2: against and optimized for. You set these in your build
Speaker 2: dot gradal file and sometimes the Android manifest dot XML.
Speaker 1: The tricky part is wanting the cool new features but
Speaker 1: not cutting off users on older phones.
Speaker 2: And that's exactly why the support library is so important.
Speaker 2: It's basically a set of libraries from Google that provide
Speaker 2: backward compatible versions of newer Android features and UI components, so.
Speaker 1: You can use modern stuff even if your mine's DK
Speaker 1: version is relatively low.
Speaker 2: Exactly, it bridges that gap lets you build more modern
Speaker 2: apps for a wider audience. Hugely valuable.
Speaker 1: Okay, environment setup? Wow. Inevitably things go wrong.
Speaker 2: Debugging debugging, Oh yeah, essential. Testing on actual physical devices
Speaker 2: is a must. You enable developer options, turn on USB debugging,
Speaker 2: connect your phone.
Speaker 1: But you also need virtual devices, right emulators.
Speaker 2: Absolutely Android virtual devices or avds. They let you quickly
Speaker 2: test on different screen sizes, different API levels without needing
Speaker 2: a drawer full of old phones.
Speaker 1: Emulators used to be painfully slow though that are much
Speaker 1: much better now.
Speaker 2: Yeah, and there are third party options to like gen
Speaker 2: Emotion or Android by eighty six which can sometimes be
Speaker 2: even faster or offer more specific simulation features.
Speaker 1: And for just checking layouts quickly.
Speaker 2: Androids Studios Layout Preview is fantastic for that you can
Speaker 2: see how your UI looks on different screen sizes, densities, themes,
Speaker 2: even landscape versus portrait, all without running the app. Massive timesaver.
Speaker 1: What about when the app is running, how do you
Speaker 1: see what's going on inside.
Speaker 2: The Android device? Monitors your friend there you can monitor
Speaker 2: things like memory usage, CPU load, network activity in real time.
Speaker 1: You can capture detailed performance data too, right the traces
Speaker 1: and stuff.
Speaker 2: Yep method tracking, resource usage, allocation tracking, plus simple things
Speaker 2: like taking screenshots or recording a video of the app running.
Speaker 1: But for just tracking the flow and seeing messages from
Speaker 1: your code.
Speaker 2: Logcat Oka definitely logcat It shows system messages errors, but
Speaker 2: the real power is adding your own log messages.
Speaker 1: So you put log dot d my tag doing this
Speaker 1: thing now in your code.
Speaker 2: And then you can filter the logcat output and Android
Speaker 2: Studio or the device monitor to see just your messages.
Speaker 2: It's way better than sticking temporary text views all over
Speaker 2: your UI to see variable values.
Speaker 1: Yeah, much cleaner. Okay, let's start building our sandwich app logic.
Speaker 1: First up, creating the basic objects, like the different types
Speaker 1: of bread or fillings. This gets us into creational patterns.
Speaker 1: The factory pattern seems foundational, it really is.
Speaker 2: The core idea is creating objects without the client code
Speaker 2: needing to know the exact class being created. You ask
Speaker 2: a factory for a object and it gives you one
Speaker 2: like our.
Speaker 1: Bread factory example. Instead of new roll or new brioche,
Speaker 1: you'd call something like breadfactory dot get bread roll exactly.
Speaker 2: The factory encapsulates the logic of which specific class to instantiate.
Speaker 2: The big win here is abstraction. How so, well, if
Speaker 2: you want to add a new bread type, say sourdough,
Speaker 2: you add the sour dough class and update the factory.
Speaker 2: The code using the factory doesn't need to change at all,
Speaker 2: as long as the factory still returns a bread object.
Speaker 2: It decouples the creation from the usage.
Speaker 1: Nice It isolates changes, and this scales up when ingredients
Speaker 1: get more complex with images, descriptions, calorie counts.
Speaker 2: Yep, the factory just handles creating those more complex objects,
Speaker 2: hiding the details.
Speaker 1: Okay, building on that. What's the abstract factory pattern?
Speaker 2: It sounds similar, It is related. If a regular factory
Speaker 2: creates one type of object like bread, an abstract factory
Speaker 2: is designed to create families of related objects. It's sometimes
Speaker 2: called a factory.
Speaker 1: Of factories, a factory of factories.
Speaker 2: Okay, so an abstract food fact three might have methods
Speaker 2: like create bread and create filling. This ensures that the
Speaker 2: bread and filling you get are compatible, may be part
Speaker 2: of the same meal deal or regional style. It enforces
Speaker 2: consistency across related object types.
Speaker 1: Got it factory for one thing, abstract factory for related
Speaker 1: sets of things. What are the builder pattern?
Speaker 2: The builder is different Again, It's specifically for constructing complex
Speaker 2: objects step by step. Instead of getting a fully formed
Speaker 2: object from a factory, a builder lets you assemble it
Speaker 2: piece by piece.
Speaker 1: Ah. Perfect for our sandwich. A sandwich isn't one simple thing.
Speaker 1: It's bread plus fillings plus toppings exactly.
Speaker 2: You'd have a sandwich builder. You'd call methods like builder
Speaker 2: dot set bread whole wheat, then builder dot ad filling
Speaker 2: Turkey builder dot adfilling, cheese, builder, dot AD topping lettuce,
Speaker 2: and finally called builder dot build to get the finished
Speaker 2: sandwich object.
Speaker 1: So it's great when an object has lots of optional
Speaker 1: parts or as specific assembly order.
Speaker 2: Precisely, it makes the construction code much more readable than
Speaker 2: having a constructor with like ten parameters, many of which
Speaker 2: might be null. It clarifies the process.
Speaker 1: Okay, we can build our sandwich object. Now let's think
Speaker 1: about how it looks.
Speaker 2: Yeah.
Speaker 1: Material design patterns are crucial for the UI absolutely.
Speaker 2: Material Design is Google's design system for Android. It provides
Speaker 2: guidelines and ready made components. Themes and styles are the foundation.
Speaker 1: That's the overall look and feel right, colors, fonts.
Speaker 2: Yeah, a theme applies styling consistently across your entire app.
Speaker 2: You can pick a base material theme and then customize
Speaker 2: it using the theme editor in Andrei Studio, defining your
Speaker 2: app's color palette, default text appearances, and so on, and.
Speaker 1: You define these colors in a resource file colors dot
Speaker 1: xml best practice.
Speaker 2: Yes, Material Design has specific recommendations for using primary, secondary,
Speaker 2: and accent colors purposefully.
Speaker 1: The guidelines get pretty specific, even down to text sizes.
Speaker 2: They do. They recommend a specific type scale like twelve
Speaker 2: P for captions, fourteen SP for body text, sixteen SP
Speaker 2: for subheadings, et cetera. Using these standard sizes helps create
Speaker 2: visual consistency and good readability.
Speaker 1: And even text color isn't just black or gray.
Speaker 2: Often no material design suggests using transparency levels on your
Speaker 2: primary text color to create secondary or disabled text states.
Speaker 2: This works better visually, especially on colored backgrounds, than just
Speaker 2: using different shades of gray.
Speaker 1: Images are vital for a food app. How does Android
Speaker 1: handle different screen densities?
Speaker 2: MDPI, ACPI, right devices have different pixel densities. To make
Speaker 2: images look sharp everywhere without wasting memory, you provide multiple
Speaker 2: versions of each image asset in density specific drawable folders, drawable, MDPA, drawable, HDPI, drawable, XHDPI,
Speaker 2: drawble XHDPI, et cetera.
Speaker 1: Do you really need all of them?
Speaker 2: Often No. For most apps, providing versions for MDPI, HDPI, XXDPI,
Speaker 2: and maybe XDFDPI covers the vast majority of device as well.
Speaker 2: The system automatically picks the best one for the device
Speaker 2: it's running.
Speaker 1: On, as long as you reference it correctly. Like at
Speaker 1: drawable my image.
Speaker 2: Exactly, you use the resource ID and Android handles selecting
Speaker 2: the right density version. It's much more efficient than just
Speaker 2: using one huge image and material guidelines suggest photographic images
Speaker 2: should be clear, simple, and have an unambiguous subject.
Speaker 1: A really common material component is the cardview. Those rounded rectangles.
Speaker 2: Yeah, they're everywhere. Cardview is great for grouping related information
Speaker 2: and image some text maybe a button about a single topic,
Speaker 2: perfect for showing our sandwich ingredients or menu items.
Speaker 1: Is known in the support library.
Speaker 2: Yep, so they work back to API level seven. A
Speaker 2: card view itself is just a container, usually with its
Speaker 2: own layout inside, like a linear layout or relative layout
Speaker 2: holding the actual content.
Speaker 1: They have a built in shadow effect to the elevation right.
Speaker 2: A default elevation of two DP, which typically increases to
Speaker 2: ADP when it's pressed or actively being interacted with gives
Speaker 2: nice visual feedback. And remember to use string resources at
Speaker 2: string ingredient name for text inside cards not hard coded
Speaker 2: strings essential for translation later.
Speaker 1: Image ratio on card matter too, right, sixteen point nine
Speaker 1: or one point one usually.
Speaker 2: Those are common guidelines for visual consistency.
Speaker 1: Yeah okay. Another core UI element the app bar or toolbar.
Speaker 2: The toolbar is the modern replacement for the old action bar.
Speaker 2: A key difference is that the toolbar is a view
Speaker 2: group you actually place inside your layout XML, giving you
Speaker 2: much more control over its position and behavior compared to
Speaker 2: the action bar You.
Speaker 1: Put the title there, maybe navigation icons action buttons like
Speaker 1: searcher settings.
Speaker 2: Exactly, and you control which action icons appear directly in
Speaker 2: the toolbar versus collapsing into an overflow menu using the
Speaker 2: show as action attribute in your MENUXML file options like
Speaker 2: if room or always again.
Speaker 1: Using string resources for titles and menu items always good practice.
Speaker 1: And the slide out navigation drawer is another standard material pattern.
Speaker 1: You mentioned something called ratio key lines for dividing vertical
Speaker 1: space in there.
Speaker 2: Ah. Yeah, that's a more subtle material guideline for components
Speaker 2: like a navigation drawer header. It suggests using scandered aspect
Speaker 2: ratios like sixteen point nine four point three one point
Speaker 2: one to defy fine key horizontal division lines based on
Speaker 2: the components with So.
Speaker 1: If the drawers say three twenty dp wide, the sixteen
Speaker 1: point nine key line would be it owned eightydp down
Speaker 1: from the top. Yeah, three twenty nine.
Speaker 2: To sixteen exactly. Using these key lines for placing major
Speaker 2: elements like the bottom of a header image can create
Speaker 2: a more visually harmonious layout. It's about structured.
Speaker 1: Proportions, interesting detail, okay. Shifting from UI to code structure
Speaker 1: and data organization structural patterns, the singleton is a well
Speaker 1: known one.
Speaker 2: The singleton pattern ensures you only ever have one instance
Speaker 2: of a particular class in your entire application, and it
Speaker 2: provides a single global way to access that instance, like the.
Speaker 1: Current user idea. Usually only one person is logged into
Speaker 1: the app at a.
Speaker 2: Time, right, It's useful for managing things that are inherently singular,
Speaker 2: like access to a shared resource, maybe a database connection pool,
Speaker 2: though that's debatable, global configuration, or yeah, the currently logged
Speaker 2: in user's data.
Speaker 1: But the source warns about overusing it definitely.
Speaker 2: Singletons can make testing harder and create tight coupling between
Speaker 2: different parts of your app if you're not careful use
Speaker 2: them thoughtfully.
Speaker 1: We talked about basic layouts, linear layout, relative layout. The
Speaker 1: source mentions using percentages for more flexible sizing.
Speaker 2: Yes, sometimes fixed dimensions or even weights don't quite give
Speaker 2: you the proportional layout you want across different screen sizes.
Speaker 2: The percent support library provides percent relative layout and percent
Speaker 2: frame layout.
Speaker 1: Letting you say this view should take up thirty percent.
Speaker 2: Of the screen with exactly layout fix percent or lay
Speaker 2: with height percent. It can help avoid distortion or awkward
Speaker 2: spacing on unusually sized screens.
Speaker 1: And for fundamentally different layouts, like for a phone versus
Speaker 1: a tablet.
Speaker 2: That's where resource qualifiers are essential. You create different layout
Speaker 2: directories named with qualifiers like reslayout sixty six hundred DP
Speaker 2: for screens with a small swidth of six hundred DP
Speaker 2: or more like small tablets, or reslay out lasex of
Speaker 2: twenty DP for larger tablets. Android automatically picks the layout
Speaker 2: from the most appropriate directory.
Speaker 1: So you might have reslayot activity main dot XML for
Speaker 1: fur phones and reslayoutsh sex six hundred deep activity main
Speaker 1: dot XML for tablets.
Speaker 2: Precisely keeps your device specific layouts separate and organized, and
Speaker 2: layout aliases can help bridge the gap for older devices
Speaker 2: that used older qualifiers like large or x large, letting
Speaker 2: them reuse your newer SWOW qualified layouts without duplicating files.
Speaker 1: Okay, our sandwich app needs lists, list of ingredients, list
Speaker 1: of menu items, list of past orders. How do we
Speaker 1: display these efficiently, especially if they get long?
Speaker 2: The modern standard for this is recycler view. It's designed
Speaker 2: specifically for displaying large or potentially large data sets efficiently.
Speaker 1: What makes it efficient?
Speaker 2: Its key feature is view recycling. Instead of creating a
Speaker 2: new view object for every single item in your list,
Speaker 2: which gets incredibly slow and memory hungry for long lists,
Speaker 2: Recycler View reuses the view objects as they scroll offscreen.
Speaker 1: So it keeps a small pool of views and just
Speaker 1: updates their content as you.
Speaker 2: Scroll exactly much much better performance. To make it work,
Speaker 2: you need three components.
Speaker 1: Okay, what are they?
Speaker 2: First? The layout manager. This determines how the items are
Speaker 2: arranged in a vertical list, linear layout manager, a grid
Speaker 2: grid layout manager, or even a staggered grid a stagger
Speaker 2: grid layout manager. The adapter. This is the bridge between
Speaker 2: your data like your list of ingredient objects, and the
Speaker 2: recycler View. It's responsible for creating the views when needed
Speaker 2: and binding your data to those views.
Speaker 1: And Third, the viewholder.
Speaker 2: This is a small helper class usually defined inside your adapter,
Speaker 2: that holds references to the actual UI elements within a
Speaker 2: single list items layout, like the text view for the
Speaker 2: ingredient name the image view for its picture. The adapter
Speaker 2: uses the viewholder to quickly update the views without needing
Speaker 2: to repeatedly call find view beyide, so.
Speaker 1: Layout manager positions things, adapter gets the data and creates
Speaker 1: updates views using viewholders. That's the flow. Now, speaking of adapters,
Speaker 1: the adapter pattern is also a structural pattern, separate from
Speaker 1: the recycler of view dot adapter component.
Speaker 2: Right, yes, good distinction. The adapter pattern is a general
Speaker 2: design pattern whose purpose is to allow two incompatible interfaces
Speaker 2: to work together.
Speaker 1: How does it do that.
Speaker 2: You create an adapter class that implements the interface the
Speaker 2: client code expects to use. Inside this adapter class holds
Speaker 2: a reference to an objects that has the interface you
Speaker 2: actually have. The adapter then translates calls from the expected
Speaker 2: interface into calls on the actual object's interface.
Speaker 1: Like the example with old location versus new location. You
Speaker 1: make an adapter that looks like new location, but internally
Speaker 1: uses an old location object to do the work exactly.
Speaker 2: It's like putting a plug adapter on your European hair
Speaker 2: dryer so you can plug it into a US socket.
Speaker 2: It converts the interface. It's often used to integrate legacy
Speaker 2: code or third party libraries that don't quite fit your
Speaker 2: current system's interfaces.
Speaker 1: Okay, and how does this differ from the bridge pattern.
Speaker 1: They sound a bit similar structurally.
Speaker 2: The key difference is intent and timing. The adapter pattern
Speaker 2: is usually applied after the fact to make existing incompatible
Speaker 2: things work together. The bridge pattern is typically designed upfront
Speaker 2: to decouple an abstraction from its implementation, So bridge is.
Speaker 1: About proactive separation.
Speaker 2: Right With bridge, you define an interface the abstraction and
Speaker 2: separate concrete implementations. The client code interacts with the interface,
Speaker 2: and you can swap out different implementations behind that interface
Speaker 2: without the client needing to know. It allows the abstraction
Speaker 2: and implementation to evolve independently. The sandwich interface being separate
Speaker 2: from how a sandwich is actually stored or built could
Speaker 2: be a bridge example.
Speaker 1: Adapter fixes incompatibility. Bridge enables independent evolution.
Speaker 2: Got it. Next up the facade pattern. This one seems simpler.
Speaker 1: It often is, but it's very useful. A facade provides
Speaker 1: a simplified, high level interface to a larger, more complex subsystem.
Speaker 1: It hides the complexity behind a single entry point.
Speaker 2: Like simplifying a complex ordering system behind a single order
Speaker 2: manager dot place order method.
Speaker 1: Perfect example, the client doesn't need to know about inventory checking,
Speaker 1: payment processing, delivery scheduling. They just talk to the.
Speaker 2: Facade makes sense, and the criteria pattern or filter pattern.
Speaker 1: This one is great for dynamically selecting objects from a
Speaker 1: collection based on different criteria. Think of filtering our list
Speaker 1: of sandwich ingredients like show me only vegetarian ingredients, or
Speaker 1: show me ingredients that are local and low calorie.
Speaker 2: Exactly. You define separate criteria objects for each condition, for example,
Speaker 2: is vegetarian criteria, is local criteria, is low calorie criteria.
Speaker 2: Then you can use them individually or combine them using
Speaker 2: logical criteria objects and criteria or criteria.
Speaker 1: So you pass your list of ingredients and the combined
Speaker 1: criteria object to a filter method and it returns just
Speaker 1: the matching ingredients precisely.
Speaker 2: It keeps the filtering logic clean, separate, and easily extensible.
Speaker 2: Adding a new filter like is gluten free criteria doesn't
Speaker 2: require changing existing code, just adding the new criteria class
Speaker 2: much better than giant Ifel's chains.
Speaker 1: Okay, we've covered buildings, structuring, and filtering. Let's get into
Speaker 1: activating patterns, making things happen in the UI and connecting
Speaker 1: the pieces. Complex scrolling behavior seems like a good place
Speaker 1: to start.
Speaker 2: Right, especially with coordinator layout. This layout is designed to
Speaker 2: coordinate interactions between its child views, particularly between scrolling views
Speaker 2: like recycler view or nested scroll view and an app
Speaker 2: bar layout.
Speaker 1: The app bar layout holds the toolbar right.
Speaker 2: Maybe other fis yes, and by setting layout scroll flags
Speaker 2: on the toolbar or other views inside the app bar layout,
Speaker 2: you control how it reacts when the content below scrolls.
Speaker 1: Like scroll makes it scroll off screen with the content.
Speaker 2: Yep exit until it collapse, makes it scroll partially off
Speaker 2: until it reaches a minimum height. Enter always makes it
Speaker 2: reappear immediately when you scroll back up. Snap makes it
Speaker 2: settle fully open or fully closed.
Speaker 1: And you can make things inside the collapsing toolbar move too,
Speaker 1: like parallax effects.
Speaker 2: Yeah, using layout collapse mode parallax on an image view
Speaker 2: inside a collapsing toolbar layout, which often wraps the content
Speaker 2: inside the app bar layout, or layout collapse mode in
Speaker 2: to make an element stick at the top. One collapsed
Speaker 2: coordinator layout enables these rich scrolling effects.
Speaker 1: And we can use our factory pattern to create the
Speaker 1: actual data list for the recycler view.
Speaker 2: Absolutely, you might have a cheese factory generate a list
Speaker 2: cheese objects which you then pass to your recycler views adapter.
Speaker 1: Let's talk about implementing that adapter. We know the concepts
Speaker 1: adapter viewholder, but what does the code look like.
Speaker 2: You'll create a class, say ingredient adapter that extends recyclerview
Speaker 2: dot adapter. Inside that, you define your viewholder class, which
Speaker 2: finds and holds references to the views in your list
Speaker 2: item layout XML as she textview ingredient name, image, view
Speaker 2: ingredient image.
Speaker 1: Then you implement the required methods in the adapter.
Speaker 2: Right on creteewholder is called when the recycler view needs
Speaker 2: a new view. Here, you inflate your item layout XML
Speaker 2: and create a new instance.
Speaker 1: Of your viewholder on bindviewholder.
Speaker 2: That's called when the recycler view wants to display data
Speaker 2: at a specific position. You get the data item for
Speaker 2: that p position from your list and use the provided
Speaker 2: viewholder to set the data on the views og holder
Speaker 2: dot ingredient name dot, set text ingredient dot, get.
Speaker 1: Name and get adam count. Just returns the size of
Speaker 1: your data list exactly.
Speaker 2: Then in your activity or fragments on create or on vcreated,
Speaker 2: you create an instance of your adapter pass at your
Speaker 2: data list. Create a layout manager and set both the
Speaker 2: layout manager and the adapter on your recycler view.
Speaker 1: You can add dividers too.
Speaker 2: Yep, using recyclview dot item decoration. There are built in
Speaker 2: helpers for simple dividers.
Speaker 1: Okay, user interaction, we need buttons like maybe a shopping
Speaker 1: cart icon action icons.
Speaker 2: Material Design has specific guidelines for icons, size, style, padding.
Speaker 2: Google provides a standard set of material icons you can
Speaker 2: easily import into Android Studio. You typically use them with
Speaker 2: image button or set them as the drawable on a
Speaker 2: regular button or menu item.
Speaker 1: And colors follow the theme usually yes.
Speaker 2: They often use the primary or secondary text colors with
Speaker 2: appropriate transparency, adapting to light or dark themes.
Speaker 1: What about confirming an action like tapping the cart icon
Speaker 1: leads to a proceed to check out?
Speaker 2: Confirmation dialogues dialogues are perfect for that alert Dialogue Builder
Speaker 2: is the standard way to create simple confirmation dialogues with titles, messages,
Speaker 2: and standard positive and negative buttons.
Speaker 1: Do you put custom stuff in them?
Speaker 2: Absolutely? You can use builder dot set view and provide
Speaker 2: your own custom layout XML file inflated. Using layout inflator,
Speaker 2: this lets you put pretty much any UI elements inside
Speaker 2: a dialogue.
Speaker 1: Cool. Another common list interaction is swiping items away, like
Speaker 1: dismissing an ingredient choice.
Speaker 2: Android provides item touch Helper for exactly this. It's a
Speaker 2: utility class that attaches to your recycler view and handles
Speaker 2: detecting swipe and dragon drop gestures.
Speaker 1: How do you use it?
Speaker 2: You create an item touch helper simple callback where you
Speaker 2: override methods like on swiped. When on swiped is called,
Speaker 2: you get the viewholder that was swiped and the direction.
Speaker 2: Inside this method, you need to remove the corresponding item
Speaker 2: from your adapter's data.
Speaker 1: List and then tell the adapter crucially yes.
Speaker 2: After removing the data, you call adapter dot notify item
Speaker 2: removed cost position, and maybe adapter dot notify item range
Speaker 2: changed position. Adapter dot get item count. So the recycler
Speaker 2: view updates its display correctly animating the removal.
Speaker 1: So item touch Helper handles the gesture detection. Your callback
Speaker 1: handles the data update notification. That's the pattern. Sometimes you
Speaker 1: might want to build layouts dynamically in code instead of
Speaker 1: just XML.
Speaker 2: It's less common for mainscreen layouts, but definitely possible and
Speaker 2: sometimes necessary for highly dynamic content. You can programmatically create
Speaker 2: instances of linear layout text, view, button, et cetera. Set
Speaker 2: their properties layout per ams text click listeners and add
Speaker 2: them to a parent layout in your activities. On create method,
Speaker 2: the source shows a simple builder like approach for this.
Speaker 1: Okay, we've got a lot of pieces. Let's think about
Speaker 1: combining patterns for more complex needs, focusing on flexibility and efficiency.
Speaker 2: Right as our sandwich app gets more sofie sticated, maybe
Speaker 2: storing favorite custom sandwiches, handling complex promotions, planning the data
Speaker 2: structures becomes really important. You need to think ahead about
Speaker 2: how data.
Speaker 1: Relates and for efficiency, especially if creating objects is slow
Speaker 1: or resource intensive, the prototype pattern can help.
Speaker 2: The prototype pattern is all about creating new objects by
Speaker 2: copying or cloning an existing object instance the prototype.
Speaker 1: Why would you do that instead of just using new.
Speaker 2: It's beneficial when object creation is computationally expensive, like maybe
Speaker 2: calculating complex nutritional info for a custom sandwich, or when
Speaker 2: you have an object already configured in a certain state
Speaker 2: and you want an exact copy of that state without
Speaker 2: repeating the configuration.
Speaker 1: Steps like the sequence generation example, calculating prime numbers is slow,
Speaker 1: so you pre calculate a sequence and then just clone
Speaker 1: it when needed exactly.
Speaker 2: The sequence cash holds prototype sequences, and the client code
Speaker 2: calls clone on a prototype. Instead of doing the expensive
Speaker 2: calculation again, you just need your class to implement the
Speaker 2: clonable interface and override the clone method correctly.
Speaker 1: Another pattern for flexibility is the decorator pattern.
Speaker 2: Decorator is really interesting. It lets you add new responsibilities
Speaker 2: or behaviors to individual objects dynamically at run time without
Speaker 2: changing the object's class. It's a flexible alternative to subclassing
Speaker 2: for extending functionality.
Speaker 1: How does that work? Sounds like magic?
Speaker 2: Think about adding options to our bread. You could have
Speaker 2: subclasses like buttered roll, toasted roll, buttered toasted roll, but
Speaker 2: that quickly leads to a class explosion. With decorator, you
Speaker 2: have your base bread object like roll. Then you have
Speaker 2: decorator classes like butter decorator and toasted decorator, which also
Speaker 2: implement the bread interface.
Speaker 1: Do you wrap the original object exactly?
Speaker 2: You create a roll, then wrap it in a butter decorator,
Speaker 2: Then wrap that in a toasted decorator. New toasted decorator,
Speaker 2: new butter decorator, new role. Each decorator adds its functionality
Speaker 2: like adding cost or changing the description, and then delegates
Speaker 2: the call to the object it wraps, so.
Speaker 1: You can mix and match decorations on the fly for
Speaker 1: any bread object.
Speaker 2: Precisely, you could add a double portion decorator for fillings too.
Speaker 2: It allows adding features and layers.
Speaker 1: It sounds a bit like the builder pattern in terms
Speaker 1: of chaining calls.
Speaker 2: The syntax can look similar, but the purpose is different.
Speaker 2: Builder constructs an object step by step. Decorator takes a
Speaker 2: fully formed object and adds extra responsibilities or modifies its
Speaker 2: behavior after it's already created. Enhancement versus construction got it.
Speaker 1: Moving on to composing patterns, building hierarchies, and making data persistent,
Speaker 1: The composite pattern seems key for hierarchies.
Speaker 2: It is The composite pattern lets you compose objects into
Speaker 2: tree structures to represent part whole hierarchies. Crucially, it allows
Speaker 2: clients to treat individual objects, leaves, and compositions of objects
Speaker 2: composits uniformly.
Speaker 1: Like Android UI layouts. A text view is a leaf.
Speaker 1: A linear layout is a composite that can hold leaves
Speaker 1: or other composites.
Speaker 2: Perfect analogy, you typically have a common component interface that
Speaker 2: both leaf objects and compositor objects implement. The composite object
Speaker 2: usually holds a list of child components and delegates. Operations
Speaker 2: like draw or calculate price to its children.
Speaker 1: So you can call the same method on a single
Speaker 1: ingredient or a whole custom sandwich object which is a
Speaker 1: composite of bread fillings, etc.
Speaker 2: Yes, the client code doesn't need to know if it's
Speaker 2: dealing with a single item or a complex group. You
Speaker 2: mentioned adding a builder to composite.
Speaker 1: Ye, and the source suggested it could simplify building complex
Speaker 1: composite structures.
Speaker 2: It definitely can. Manually creating and nesting composite objects in
Speaker 2: code can get for both. A builder can provide a
Speaker 2: cleaner API for assembling the tree.
Speaker 1: Okay, structures are great, but our app needs to remember things.
Speaker 2: Persistent data storage essential for user settings, saved orders, preferences.
Speaker 2: Android offers several ways for static unchanging text. Putting text
Speaker 2: files in the resrowd directory is simple. They get compiled
Speaker 2: into the app. You read them using an input stream.
Speaker 2: Good for help text terms and conditions, stuff that doesn't change.
Speaker 2: External storage is more for user gen generrated files or
Speaker 2: sharing between apps.
Speaker 1: But for user preferences like their default delivery address or
Speaker 1: maybe dietary flags.
Speaker 2: Shared preferences is the go to for simple key value data.
Speaker 2: It's perfect for storing user settings. You get a shared
Speaker 2: preferences object, use an editor to put values, strings, booleans, integers,
Speaker 2: and call apply to save them asynchronously.
Speaker 1: And usually load them in on create and save them
Speaker 1: in on pause.
Speaker 2: That's a common pattern. Yeah, apply saves in the background
Speaker 2: so it doesn't block the UI thread, unlike the older
Speaker 2: commit method.
Speaker 1: The source mentioned a neat trick using shared preferences for
Speaker 1: first run detection.
Speaker 2: Yeah, you can store a boolean flag like is a
Speaker 2: first run check for it when the app starts. If
Speaker 2: it's not there or true, you know it's the first launch,
Speaker 2: show your onboarding, and then set the flag to false.
Speaker 2: Another way is to generate and store a unique ID
Speaker 2: using Java dot util dot uid on the first run.
Speaker 2: If the ID exists on subsequent launches, it's.
Speaker 1: Not the first run clever, okay. Let's shift to how
Speaker 1: different parts of the app communicate and react to events,
Speaker 1: observing patterns.
Speaker 2: This involves patterns that help manage dependencies and notifications between objects,
Speaker 2: essential when the app isn't actively in the foreground. User
Speaker 2: notifications are key here.
Speaker 1: Things that appear in the status bar right.
Speaker 2: Usually triggered by background components like services. They alert the
Speaker 2: user to something important, even if they're not using the
Speaker 2: app right now.
Speaker 1: The observer pattern underlies.
Speaker 2: A lot of this, doesn't it It does. The observer
Speaker 2: pattern defines a one to many dependency between objects. When
Speaker 2: one object, the subject or observable, changes state, all its
Speaker 2: dependents observers are notified automatically.
Speaker 1: Like our sandwich object could be the subject and an
Speaker 1: order object could be an observer. When the sandwich is
Speaker 1: marked ready, the order gets notified exactly.
Speaker 2: The observer registers itself with the subject, and the subject
Speaker 2: calls a specific method like update on all its registered
Speaker 2: observers when its state changes. Java even has built in
Speaker 2: Java dot util dot observer and Java dot util dot
Speaker 2: observable classes, though newer approaches using libraries like love data
Speaker 2: or arcs java are often preferred.
Speaker 1: Now, how does this relate to the Android Notifications API?
Speaker 2: The system notifications you see in the status bar are
Speaker 2: a way for your app, often a background service acting
Speaker 2: as an observer of some event, to notify the user.
Speaker 2: The API lets you build these notifications, and it can
Speaker 2: be more.
Speaker 1: Than just text. Right actions, big pictures?
Speaker 2: Oh yeah, You use notification compat dot builder to construct them.
Speaker 2: You can set icons, titles, text, vibration patterns, You can
Speaker 2: add actions like buttons within the notification using pending intents
Speaker 2: that trigger something in your app when tapped. You can
Speaker 2: create expanded notifications with big text style, big picture style,
Speaker 2: or inbox style to show more content, and.
Speaker 1: Newer Android versions have heads up notifications.
Speaker 2: API twenty one plus introduced heads up notifications that slide
Speaker 2: in briefly at the top and lock screen notifications. You
Speaker 2: need to set priorities and visibility flags visibility, public, visibility, private,
Speaker 2: et cetera to control where and how your notifications appear
Speaker 2: and use them judiciously for important timely info.
Speaker 1: You mentioned services triggering these What are services?
Speaker 2: Services are Android components designed for running long running operations
Speaker 2: in the background without a user interface. Think playing music,
Speaker 2: downloading files, or in our case, maybe monitoring an order
Speaker 2: status or setting a reminder timer.
Speaker 1: So a service could run, detect the sandwiches ready, and
Speaker 1: then use the Notifications API to tell the user exactly.
Speaker 2: Services have their own life cycle on create, on start, command,
Speaker 2: on destroy. It's crucial to manage their life cycle correctly,
Speaker 2: especially stopping them stop service or stop self when their
Speaker 2: work is done to avoid draining battery.
Speaker 1: Okay, moving towards more complex interactions and algorithms behavioral patterns.
Speaker 2: These patterns focus on how objects collaborate and distribute responsibilities
Speaker 2: to accomplish tasks.
Speaker 1: The template pattern is first.
Speaker 2: Template defines the skeleton of an algorithm in a base class,
Speaker 2: often abstract, but let subclasses override specific steps of that
Speaker 2: algorithm without changing the overall structure.
Speaker 1: So the base class provides the template the fixed sequel
Speaker 1: of steps, and subclasses fill in the implementation details for
Speaker 1: some of those steps precisely.
Speaker 2: Like a prepare sandwich template method in a base class
Speaker 2: might call abstract methods get bread, ad fillings, add toppings.
Speaker 2: Concrete subclasses like prepare clip sandwich or prepare veggie sandwich
Speaker 2: would implement those abstract methods differently, but the overall prepare
Speaker 2: sandwich sequence remains the same.
Speaker 1: Got it enforces structure, allows variation in steps. How does
Speaker 1: this strategy pattern compare.
Speaker 2: Strategy also deals with algorithms, but its focus is on
Speaker 2: making a family of algorithms interchangeable. You encapsulate each algorithm
Speaker 2: into a separate strategy object, and the context object holds
Speaker 2: a reference to one of these strategies and delegates the
Speaker 2: algorithmic task to it.
Speaker 1: The key difference being you can swap the strategy at
Speaker 1: run time.
Speaker 2: Yes, that's the main distinction from template, where the implementation
Speaker 2: is fixed by the subclass at compile time. With strategy,
Speaker 2: the context object can change which strategy it uses whenever needed.
Speaker 1: Like having different delivery strategies flat rate strategy, distance based strategy,
Speaker 1: rush hour strategy, and choosing the right one based on
Speaker 1: the order time or location.
Speaker 2: Perfect example, the order object the context would hold a
Speaker 2: pricing strategy object and call its calculate price method. You
Speaker 2: can easily swap in a different strategy object to change
Speaker 2: the pricing logic.
Speaker 1: Okay. The visitor pattern seems a bit more involved.
Speaker 2: Visitor lets you add new operations to a set of
Speaker 2: existing classes without modifying those classes. It separates the algorithm
Speaker 2: from the object structure.
Speaker 1: It operates on supermarket analogy. The cashier visitor knows how
Speaker 1: to process different items visited elements without the items needing
Speaker 1: to know about the cashier specific process exactly.
Speaker 2: You have an item interface with an accept visitor v method.
Speaker 2: Concrete items, bread, filling, drink implement this method, usually by
Speaker 2: calling visitor dot visit this. Then you have a visitor
Speaker 2: interface with overloaded visit methods for each concrete item type
Speaker 2: visit breadbe, visit filling F.
Speaker 1: So a calculat price visitor would implement visit breadbe to
Speaker 1: get the bread price, visit filling F to get the
Speaker 1: filling price, et cetera.
Speaker 2: Right, and later you could add a generate nutritional info
Speaker 2: visitor with its own set of visit methods, all without
Speaker 2: ever changing the bread, filling, or drink classes. It avoids
Speaker 2: polluting your element classes with lots of different operations and
Speaker 2: makes adding new operations easier.
Speaker 1: Useful for complex processing on diverse object structures. Finally, the state.
Speaker 2: Pattern state allows an object to alter its behavior when
Speaker 2: its internal state changes to the outside world. The object
Speaker 2: appears to change its class.
Speaker 1: Like the turnstyle example, it behaves differently push coin depending
Speaker 1: on whether it's in the locked or unlocked state.
Speaker 2: Yes, you define a state interface and concrete state classes
Speaker 2: lock state, unlocked state. The context object the turnstyle holds
Speaker 2: a reference to its current state object. When a method
Speaker 2: like push is called on the context, it delegates the
Speaker 2: call to the current state object current stage out push
Speaker 2: the state object handles the logic for that state, and
Speaker 2: can also change the context's current state to transition it
Speaker 2: context dot sets state.
Speaker 1: Unlock state, so the behavior logic is encapsulated within each
Speaker 1: state class. Makes handling state dependent behavior much cleaner than
Speaker 1: massive I, false or switch statements in the context.
Speaker 2: Object exactly very useful for modeling anything with distinct states
Speaker 2: and transitions, like workflows, game characters, connection statuses.
Speaker 1: We've mostly talked phone tablet but Android is on watches, TVs, cars,
Speaker 1: wearable patterns, and other form factors.
Speaker 2: Right. Developing for Android ware, now Ware OS, Android TV,
Speaker 2: and Android Auto presents different challenges and opportunities. Screen size,
Speaker 2: input methods, user context all very different.
Speaker 1: Android TV big screen remote control input yeah.
Speaker 2: Ten foot UI experience. Androids Studio has TV module templates.
Speaker 2: You'll use the leanback support library for TV specific UI
Speaker 2: components like rows and grids optimized for remote navigation. The
Speaker 2: MVP model view presenter pattern is often recommended for structuring the.
Speaker 1: App logic and specific requirements for things like recommendation card
Speaker 1: background images.
Speaker 2: Yes, very specific dimensions and bleed requirements much larger than
Speaker 2: typical phone assets. Graphics quality really matters on a big
Speaker 2: TV screen.
Speaker 1: Than tiny screens.
Speaker 2: Android ware os often companion apps linked to a phone,
Speaker 2: but increasingly capable standalone apps too. They have access to
Speaker 2: unique sensors like heart rate monitors, opening new possibilities. Maybe
Speaker 2: our sandwich app suggests healthier options based on your activity level.
Speaker 1: The big challenge there are screen shape right square versus.
Speaker 2: Round YEP two main approaches. Create separate layout files for
Speaker 2: square and round screens reslayout and reslay out round, or
Speaker 2: use the watch view stub component in your layout. Watch
Speaker 2: v stub detects the screen shape at runtime and inflates
Speaker 2: either erect layout or round layout you.
Speaker 1: Specify reading sensors like heart rate.
Speaker 2: Uses the standard Android sensor manager and sensor event listener
Speaker 2: in her face, just like on a phone, Get the manager,
Speaker 2: get the default sensor EVEG sensor dot type, hart rate,
Speaker 2: register your listener and get data in on sensor changed.
Speaker 2: Always check if the sensor actually exists on the specific watch.
Speaker 1: Model first, and Android auto safety is paramount.
Speaker 2: Absolutely number one priority. App functionality is heavily restricted to
Speaker 2: minimize driver distraction. Primarily it's for audio, music apps and
Speaker 2: messaging apps.
Speaker 1: Strict guidelines and testing very strict.
Speaker 2: Google has detailed design guidelines about layout, font sizes, interaction models.
Speaker 2: Voice input is key. Avoiding animations or delays you need
Speaker 2: to use autosimulators for testing. App configuration involves manifest meather data,
Speaker 2: linking to an XML descriptor file, declaring the app type
Speaker 2: media or messaging, and requiring specific background services.
Speaker 1: Okay, to get our app out there and maybe make
Speaker 1: some money. Social patterns and distribution patterns.
Speaker 2: Social integration can be a huge boost for discovery and
Speaker 2: engagement likes shares.
Speaker 1: The webew component seems versatile here it is.
Speaker 2: WebView lets you display web pages directly inside your app.
Speaker 2: Back to useful for showing help documentation, hosted online terms
Speaker 2: of service, or even building parts of your app using webtech.
Speaker 2: If content needs frequent updates without pushing an app update
Speaker 2: needs the Internet permission obviously.
Speaker 1: Just add it to your layout and call load to role.
Speaker 2: Basically yes. For more advanced stuff, you can enable JavaScript
Speaker 2: and use the JavaScript interface. This lets your web page's
Speaker 2: JavaScript call native Java methods in your Android app.
Speaker 1: How does that work?
Speaker 2: You create a Java class with methods annotated at JavaScript interface.
Speaker 2: You add an instance of this class to the WebView
Speaker 2: using ad JavaScript interface. Then JavaScript code in the webpage
Speaker 2: can call those annotated methods directly, allowing two way communication. Powerful,
Speaker 2: but needs careful security considerations.
Speaker 1: For direct social sharing.
Speaker 2: Facebook requires the Facebook SDK. You add it as a
Speaker 2: dependency set up a Facebook app I d add it
Speaker 2: to your strings, dot xml and manifest. Then you can
Speaker 2: use their pre built UI components like like view or
Speaker 2: share button directly in your layouts. Sharing content links photos
Speaker 2: is done via their API, usually requiring a content provider
Speaker 2: set up in your manifest. For sharing local files, their
Speaker 2: sharing Debugger tool is essential for testing how your shared
Speaker 2: posts will look. Pure similar idea, you can use the
Speaker 2: Twitter SDK, often integrated via fabric Firebase, for simple tweeting.
Speaker 2: You might even just use an intent with a specific
Speaker 2: Twitter dot Com intent tweet url structure. The SDK offers
Speaker 2: more for timelines, direct messaging, et cetera.
Speaker 1: Finally, getting the app to users distribution.
Speaker 2: Before you publish anywhere, crucial checks remove all log statements
Speaker 2: used for debugging, ensure your app has a proper application
Speaker 2: label ANDROIDBAT label in icon, android dot icon defined in
Speaker 2: the Android manifest dot xml, and double check that all
Speaker 2: required permissions uses permission are declared.
Speaker 1: In the manifest. The main distribution channel is.
Speaker 2: Google play Right that involves generating a signed release build
Speaker 2: APK or the preferred Android app bundle AaB, registering for
Speaker 2: a Google Play Developer account, which has a one time fee,
Speaker 2: and uploading your app bundle through the Play console, filling
Speaker 2: in store, listing details, screenshots.
Speaker 1: Et cetera. Are there other options?
Speaker 2: Sure, you can host the apkab on your own website
Speaker 2: for direct download or distribute it via email or other platforms,
Speaker 2: but Google Play offers the widest reach. Automatic updates and
Speaker 2: discovery features.
Speaker 1: And making money monetization.
Speaker 2: Two main routes in at billing, selling digital goods or
Speaker 2: subscriptions and advertising.
Speaker 1: In that billing sounds complex.
Speaker 2: It can be. Google provides the Play Billing Library, which
Speaker 2: simplifies it greatly compared to the older ADL approach mentioned
Speaker 2: in some sources. You add the library dependency, use the
Speaker 2: billing client API to query products, launch purchase flows, and
Speaker 2: handle purchases. You still need the colm dot Android dot
Speaker 2: vending dot billing permission and need to set up your
Speaker 2: products in Play console. Security, like verifying purchases on your.
Speaker 1: Server is important, and ads usually Google ad Mob.
Speaker 2: That's the most common. You need an ad mob account.
Speaker 2: Add the Google Mobile Ads SDK dependency part of Google
Speaker 2: Play services. Add Internet and access network state permissions to
Speaker 2: your manifest plus some metadata and an AD activity declaration.
Speaker 1: Then put an adview in the layout yep.
Speaker 2: Add an adview to your XML layout, configure its size
Speaker 2: and your unique AD unit ID. Then in your activity code,
Speaker 2: create an AD request and call adview dot loaded ad request. Crucially,
Speaker 2: during development, make sure you can figure it to request
Speaker 2: test ads, either by registering your device ID or using
Speaker 2: the emulator so you don't violate ad MOB policies.
Speaker 1: Wow. Okay, so we've gone from the basic idea of
Speaker 1: a sandwich app through defining patterns, building UI for different devices,
Speaker 1: handling data, background tasks, social features, all the way to
Speaker 1: publishing and monetizing.
Speaker 2: It really highlights how these patterns weave through the entire
Speaker 2: development process. They provide structure, solve recurring problems, and guide
Speaker 2: you towards writing code that's more robust, flexible, and maintainable.
Speaker 2: They're not just academic exercises, the practical tools for building
Speaker 2: better software.
Speaker 1: Seeing how factory helps create ingredients, builder assembles the same
Speaker 1: now which rule like review displays lists, observer handles updates,
Speaker 1: state manages, order progress. It makes the value really clear exactly.
Speaker 2: They give you a shared language and proven approaches to
Speaker 2: common challenges.
Speaker 1: So maybe the final thought for everyone listening is this.
Speaker 1: As you start your next project, or even just tackle
Speaker 1: a new feature, pause for a moment. Think about the
Speaker 1: problem you're trying to solve. Is there a pattern here?
Speaker 1: Could applying a pattern like decorator, strategy or facade simplify
Speaker 1: your design, make it more flexible, or prevent future headaches.
Speaker 1: Howmit thinking about patterns from the start, change the way
Speaker 1: you approach building, not just for phones, but for the
Speaker 1: whole diverse ecosystem of Android devices.