AAD-Preparation

Associate Android Developer Study Guide
https://developers.google.com/training/certification/associate-android-developer/study-guide/

Navigation

• Material design
• Localisation
• Device compatibility
• Lifecycle
• App components
• Working in the background
• Notification
• Accessibility Features
• Day/Night Mode
• Styles
• Jetpack
• Debugging
• Test
• Kotlin

Material design

Add the material dependency in build.gradle

implementation 'com.google.android.material:material:1.0.0'

• Toast vs Snackbar

	Toast	Snackbar
Overview	A toast provides simple feedback about an operation in a small popup	Snackbars provide lightweight feedback about an operation
Interaction	Toasts automatically disappear after a timeout	Snackbar could either automatically disappear after a timeout, or be manually closed
More info		1. Having a CoordinatorLayout in your view hierarchy allows Snackbar to enable certain features 2. Snackbars can contain an action such as "undo"
Sample code	BaseActivity	BaseActivity

Read more - Toasts
Read more - Snackbar

Layouts

• AppBarLayout -> [Any activity in this app
• BottomSheet -> ContentProviderFragment
• Chip -> NotificationActivity
• ConstraintLayout -> rv_album_item
• FloatingActionButton -> MainActivity
• MaterialButton -> BackgroundServiceFragment
• MaterialCardView -> BackgroundActivity
• NavigationView -> MainActivity
• RadioGroup -> BackgroundActivity
• Seekbar (sliders) -> BackgroundActivity
• TabLayout -> AppComponentsActivity
• TextInputLayout, TextInputEditText -> NotificationActivity
• RecyclerView (grid) -> ArtistsFragment
• RecyclerView (linear) -> AlbumsFragment
• RecyclerView (drag + swipe) -> PlaylistFragment, PlaylistAdapter, RecyclerViewItemTouchHelper
• RecyclerView (SelectionTracker) -> ArtistsFragment, ArtistAdapter, ArtistItemKeyProvider, ArtistItemDetailsLookup
  SelectionTracker is another to do setOnClickListener, which is more powerful while multiple items need selecting
• BottomNavigationView -> UIComponentsActivity
• TabLayout + ViewPager -> MusicFragment, UIComponentsActivity
• SearchView -> SearchSongsActivity, AndroidManifest

SearchView

Believe if or not, a SearchView could be far more complicated than you've expected.
Before we get started, let's take a look at some features of SearchView:

• Search Interface
• Query suggestion (either recent searches or custom suggestions)
• Query history
• Searchable configuration (E.g. voice search)

Read more

First thing first, you need to create either Search Dialog (a SearchView inside NavigationView) or Search Widget (your custom search view, which could be an EditText placed anywhere in your layout).

Secondly, think about how you handle the search view. Here is my workflow:

1. Start the SearchSongsActivity
2. User types something in SearchView and press enter
3. Start the SearchSongsActivity again
4. Handle searches in onNewIntent()

You need the following:

1. Add tags to your result activity in AndroidManifest.xml

<activity
    android:name=".activities.SearchSongsActivity"
    android:launchMode="singleTop">

    <intent-filter>
        <action android:name="android.intent.action.SEARCH" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
    </intent-filter>

    <intent-filter>
        <action android:name="com.google.android.gms.actions.SEARCH_ACTION" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
    </intent-filter>

     <meta-data
        android:name="android.app.searchable"
        android:resource="@xml/searchable" />
</activity>

2. In xml/searchable.xml

<?xml version="1.0" encoding="utf-8"?>
<searchable xmlns:android="http://schemas.android.com/apk/res/android"
    android:hint="@string/search_hint"
    android:label="@string/app_name"
    android:searchSuggestAuthority="com.catherine.materialdesignapp.providers.SearchSuggestionProvider"
    android:searchSuggestSelection=" ?"
    android:voiceSearchMode="showVoiceSearchButton|launchRecognizer" />

android:searchSuggestAuthority": (Optional) Refer to your search content provider
android:searchSuggestSelection": (Optional) Pop up search suggestions, " ?" means query
android:voiceSearchMode": (Optional) To enable voice search
Read more search configuration here: https://developer.android.com/guide/topics/search/searchable-config

(Optional) Create your search suggestion content provider

public class SearchSuggestionProvider extends SearchRecentSuggestionsProvider {
    public final static String AUTHORITY = "com.catherine.materialdesignapp.providers.SearchSuggestionProvider";
    public final static int MODE = DATABASE_MODE_QUERIES | DATABASE_MODE_2LINES;

    public SearchSuggestionProvider() {
        setupSuggestions(AUTHORITY, MODE);
    }
}

And register your content provider in AndroidManifest.xml

<provider
    android:name=".providers.SearchSuggestionProvider"
    android:authorities="com.catherine.materialdesignapp.providers.SearchSuggestionProvider" />

3. Handle intents and create a search icon in your activity

public class SearchSongsActivity extends AppCompatActivity {  
    private final static String TAG = SearchSongsActivity.class.getSimpleName();  
    private SearchManager searchManager;
    private SearchView searchView;

  /**
     * In this case, this onNewIntent will be called while
     * user finishes searching, this activity will be relaunch.
     * <p>
     * Because
     * 1. this activity launches in single top/task/instance mode
     * 2. ACTION_SEARCH is defined in intent-filter
     *
     * @param intent
     */
    @Override
    protected void onNewIntent(Intent intent) {
        handleIntent(intent);
    }

    private void handleIntent(Intent intent) {
        if (intent == null)
            return;
        if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
            String query = intent.getStringExtra(SearchManager.QUERY);

            // Handle the scenario that user submitted searches:
            // 1. Fill in what user just typed in SearchView automatically
            // 2. Dismiss search suggestions
            // 3. Query
            // 4. Save queries
            searchView.setQuery(query, false);
            searchView.clearFocus();
            query(query);
            saveQueries(query);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.searchable_menu, menu);

        searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
        searchView = (SearchView) menu.findItem(R.id.action_search).getActionView();
        searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_clear:

                // clear query history
                SearchRecentSuggestions suggestions = new SearchRecentSuggestions(this,
                        SearchSuggestionProvider.AUTHORITY, SearchSuggestionProvider.MODE);
                suggestions.clearHistory();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    private void query(String text) {
        // do something
    }

    // save queries while you've defined a search content provider.
    private void saveQueries(String text) {
        SearchRecentSuggestions suggestions = new SearchRecentSuggestions(this,
                SearchSuggestionProvider.AUTHORITY, SearchSuggestionProvider.MODE);
        suggestions.saveRecentQuery(text, null);
    }
}

4. In menu/ui_components_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/action_search"
        android:actionLayout="@layout/searchview_layout"
        android:icon="@drawable/ic_search_black_24dp"
        android:title="@string/action_search"
        app:actionViewClass="androidx.appcompat.widget.SearchView"
        app:showAsAction="ifRoom|collapseActionView" />
</menu>

app:showAsAction="collapseActionView": Click the search icon and stretch the view
setIconified(false): Always show the search field

Custom Layouts

Build a custom view from scratch:

1. Slider
2. attrs
3. BackgroundServiceFragment, fragment_background_service

Localisation

List all resource directories you should take care of:

1. animator/
2. anim/
3. color/
4. drawable/
5. mipmap/
6. layout/
7. menu/
8. raw/
9. values/
10. xml/
11. font/

Device compatibility

1. Create alternative UI resources such as layouts, drawables and mipmaps
2. Set layout files with the following rules:
   • Avoid hard-coded layout sizes by using wrap_content, match_parent and layout_weight, etc
   • Prefer ConstraintLayout
   • Redraw views when window configuration changes (multi-window mode or screen rotation)
3. Define alternative layouts for specific screen sizes. E.g. layout-w600dp and layout-w600dp-land for 7” tablets and 7” tablets in landscape representative
4. Create stretchable nine-patch bitmaps
5. Build a dynamic UI with fragments
6. Test on all screen sizes

ConstraintLayout example: []
Fragments example: []

Read more

Pixel densities

Pixel density is how many pixels within a physical area of the screen, dpi is the basic unit.

dpi: Dots per inch
resolution: The total number of pixels on a screen
dp or dip: Instead of px (pixel), measure UI with dp (density-independent pixels) on mobile devices

UI Spec

	ldpi	mdpi	hdpi	xhdpi	xxhdpi	xxxhdpi
Scaling ratio	0.75x	1x	1.5x	2x	3x	4x
Dpi	~120dpi	~160dpi	~240dpi	320dpi	480dpi	640dip
App icon size	36x36 px	48x48 px	72x72 px	96x96 px	144x144 px	192x192 px

nodpi: bitmaps in nodpi drawables look larger in xhdpi devices whereas it seems smaller on mdpi devices.
anydpi: These bitmaps in anydpi have priority when no bitmaps are found in other drawable directories. For instance, we have drawable-hdpi/banner.9.png and drawable-anydpi/banner.xml, banner.9.png will be used on hdpi devices and banner.xml will be seen on other devices.

To see more details by automatically importing icons with Android Studio Image Asset tools and have a look at Grid and keyline shapes

res directory example: res

Read more

Lifecycle

Read more

Saving UI states

1. ViewModel
2. onSaveInstanceState()
   To test savedInstanceState, have Do not keep activities selected on system Settings page to test onSaveInstanceState and onRestoreInstanceState
   Code: LifecycleActivity
3. Persistent in local storage for complex or large data

Read more

Monitor lifecycle events via Lifecycle class in two ways:

1. Implement both LifecycleObserver and LifecycleOwner
   Code: LifecycleActivity, LifecycleObserverImpl

2. Associate with Jetpack

Read more

Handle configuration changes

1. Enable activities to handle configuration changes like screen rotation and keyboard availability change

<activity android:name=".MyActivity"
          android:configChanges="orientation|keyboardHidden"
          android:label="@string/app_name">

2. In activities

 @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // do something
    }

Code: BaseActivity
Read more

App components

There are four different types of app components:

• Activity
• Services
• Broadcast receivers
• Content providers

Read more

Activity

4 Launch Modes

<activity
    android:name=".SingleTaskActivity"
    android:launchMode="singleTask">

Let's say we have 4 activities: A, B, C and D

1. standard

• Default mode, it pushes new activities on the top of the stack.
• Example (how activities work in the stack): (bottom) A-B-B-D-A-C-C (top)

2. singleTop

• No duplicate activities on the top, but there could be same activities in the stack.
• Example (how activities work in the stack): (bottom) A-B-A-C-D-C (top)
• Let's say C is the top activity, and you try to launch C again. Then this C won't be created, instead, onNewIntent() will be called in existed C.

3. singleTask

• No duplicate activities in the stack.
• Example (how activities work in the stack): (bottom) A-B-C-D (top)
• Let's say C is in the stack, and you try to launch C again. Then this C won't be created, instead, onNewIntent() will be called in existed C.
• Don't forget to set taskAffinity (android:taskAffinity="your packageName") to map the activity to app.

4. singleInstance

• singleTask + taskAffinity is more recommended.
• No duplicate activities in the system, which means if there is A running in App1, then we lunch A in App2, this running A in App1 will be killed.
• Example (how activities work in the stack): (bottom) A-B-C-D (top)
• Let's say C is in the stack, and you try to launch C again. Then this C won't be created, instead, onNewIntent() will be called in existed C.
• You could set taskAffinity (android:taskAffinity="your packageName") as well

NOTICE: You might need to handle both onCreate() and onNewIntent() lifecycle events in singleTop

Fragment

1. To build a multi-pane UI
2. To reuse fragments in multiple activities.
3. A fragment must always be hosted in an activity and the fragment's lifecycle is directly affected by the host activity's lifecycle.

Code (Activity + Fragment): UIComponentsActivity
Code (ViewPager + Fragment): MusicFragment
Read more

Services

• Two services in Android - background service and foreground service
• Background services are no longer working since Android Oreo, you are suppose to use JobScheduler instead.
• Foreground services and JobScheduler are alternatives to run app in the background, but notification is required while running a foreground service.
• JobScheduler is only available on devices running API 21+. Fore devices running API 14+ including devices without Google Play serivces, WorkManager let you schedule background tasks that need guaranteed completion, whether or not the app process is running.

Android API level	background service	foreground service	job scheduler
≤ 25	O	X	X
≥ 26	X	O	O

JobScheduler TIPS:

1. Because setting this property is not compatible with persisted jobs, doing so will throw an IllegalArgumentException when JobInfo.Builder.build() is called.
2. jobScheduler.cancel(JOB_ID) or jobScheduler.cancelAll() only works while jobs haven't started. For example, a job is scheduled to start in 5 seconds (setMinimumLatency(5000)), cancel() works right before the job actually runs.
3. Don't forget to finish jobs if the task is done. (jobFinished(jobParameters, false))

Code: BackgroundServiceFragment, MusicPlayerService, MusicPlayerJobScheduler, AndroidManifest
Read more

Broadcast receiver

You could either register receivers by dynamically extending BroadcastReceiver or statically declaring an implementation with the <receiver> tag in the AndroidManifest.xml

Code: NetworkHealthService, NetworkHealthJobScheduler, InternetConnectivityReceiver
Read more

Content Provider

Create your own content providers to share data with other applications or access existing content providers in another applications.

System content providers

In order to get the uri path, we are going to have a look at android source code.

1. Go to https://android.googlesource.com/platform/packages/providers/ContactsProvider/+/master/ and pick out needed providers
2. Search <provider> tag in AndroidManifest, e.g.

<provider 
    android:name="CallLogProvider"
    android:authorities="call_log"
    android:syncable="false" android:multiprocess="false"
    android:exported="true"
    android:readPermission="android.permission.READ_CALL_LOG"
    android:writePermission="android.permission.WRITE_CALL_LOG">
</provider>

To read call logs, ask for READ_CALL_LOG permission.
3. Now we have the host name (android:authorities), then go to CallLogProvider, which refers to android:name, and get the table name
4. Search UriMatcher in CallLogProvider, you will find a bunch of sURIMatcher.addURI().

static {
    sURIMatcher.addURI(CallLog.AUTHORITY, "calls", CALLS);
    sURIMatcher.addURI(CallLog.AUTHORITY, "calls/#", CALLS_ID);
    sURIMatcher.addURI(CallLog.AUTHORITY, "calls/filter/*", CALLS_FILTER);
    // Shadow provider only supports "/calls".
    sURIMatcher.addURI(CallLog.SHADOW_AUTHORITY, "calls", CALLS);
}

5. The completely path would be: scheme (content://) + table_name (authorities) + path (defined uriMatcher)

private final static Uri callLogsDB = Uri.parse("content://call_log/calls");

6. Fetch call logs
   You are able to query call logs, register observers to listen to fetch events like incoming calls, outgoing calls, etc.
   Check all fields you can query: CallLogProvider, CallLog

Code: CursorLoaderActivity

User-defined content providers

A content provider uri should be scheme + authority + table + [id] + [filter]. E.g. content://com.catherine.myapp/member/1/name

ContactsProvider + CallLogs code: ContentProviderFragment

Define your own content provider

Working in the background

Tasks on a background thread using AsyncTask (for short or interruptible tasks) or AsyncTaskLoader (for tasks that are high-priority, or tasks that need to report back to the user or UI).

AsyncTask

• run on UI thread: onPreExecute, onProgressUpdate and onPostExecute
• update progress to UI via publishProgress, handle data in onProgressUpdate
• WeakReference
• executeOnExecutor

Code: BackgroundActivity, SleepTask

AsyncTaskLoader

When you want the data to be available even if the device configuration changes, use loaders
This getLoaderManager() or getSupportLoaderManager() is deprecated since Android P. Instead, we use ViewModels and LiveData

• Call getLoaderManager() or getSupportLoaderManager() depends on whether you use Support Library
• initLoader is supposed to be called in onCreate()
• Call restartLoader is equivalent to initLoader, but initLoader only works at the first time.
• onLoadFinished is run on background thread, this may cause memory leak if updating UI here - use at your own risk.

Code: BackgroundActivity, SleepTaskLoader

ViewModels and LiveData

Notification

Three style of notifications:

1. Standard notification
2. Notification with actions (one or two buttons)
3. Replying notification

Notification dots (Badge)

Long click app icons on Android O+ devices, notification badge will pop up.

Notification Channels

Classify notifications by channels in the Settings app on Android O+ devices.

Code: NotificationActivity
Read more

Accessibility Features

1. Set ContentDescription
2. Make the views focusable

Day/Night Mode

1. Define your own style in styles.xml, notice your style must extend whatever styles contain ".DayNight" keyword.

<style name="AppTheme.NoActionBar" parent="Theme.MaterialComponents.DayNight.NoActionBar">
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

or

<style name="AppTheme" parent="AppTheme.DayNight">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
</style>

In Manifest, update the theme

android:theme="@style/AppTheme.NoActionBar"

3. Initialise night mode programmatically if you want

public class MainActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        initNightMode();
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    // We set the theme, immediately in the Activity’s onCreate()
    private void initNightMode() {
        Storage storage = new Storage(this);
        int nightMode = storage.retrieveInt(Storage.NIGHT_MODE);
        if (nightMode == AppCompatDelegate.MODE_NIGHT_YES) {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
        } else {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
        }
    }
}

4. Switch day/night mode programmatically if you want

SharedPreferences sharedPreferences = getSharedPreferences("main", Context.MODE_PRIVATE);
button.setOnClickListener(
    v -> {
        int nightMode = AppCompatDelegate.getDefaultNightMode();
        if (nightMode == AppCompatDelegate.MODE_NIGHT_YES) {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
            button.setTitle(getString(R.string.action_night_mode));
            sharedPreferences.edit().putInt("night_mode", AppCompatDelegate.MODE_NIGHT_NO).apply();
        } else {
            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
            item.setTitle(getString(R.string.action_day_mode));
            sharedPreferences.edit().putInt("night_mode", AppCompatDelegate.MODE_NIGHT_YES).apply();
        }
        // Recreate the activity for the theme change to take effect.
        recreate();
    }
);

Code: BaseActivity Read more

Styles

To inherit styles from Android support library by using parent

<style name="GreenText" parent="TextAppearance.AppCompat">
    <item name="android:textColor">#00FF00</item>
</style>

And to inherit user-defined styles, you could use a dot notation

<style name="GreenText.Large">
    <item name="android:textSize">22dp</item>
</style>

Code: styles

Jetpack

Video
Guide

Room

A robust SQLite object mapping library.

WorkManager

WorkManager providers APIs for deferrable, one-off and recurring background tasks that need guaranteed execution

ViewModel

ViewModel is constructed when app configuration changes such as screen rotation

LiveData

LiveData is an observable data holder for the data is meant to be shown on screens.

Paging

Paging library integrates directly with endless data

Navigation

Navigation library simplifies implementation of complex but common navigation requirements.

Go to google tutorial to see how Room + ViewModel + LiveData works.

Code(Room + ViewModel + LiveData): PlaylistFragment, AlbumsFragment, ArtistsFragment and jetpack

Migrate to AndroidX

1. In order to activate AndroidX, add two flags in gradle.properties

android.useAndroidX=true
android.enableJetifier=true

2. Remove android support libraries com.android.support... and android.arch..., all the changes must be implemented to both classes and layouts.

3. Update test options in build.gradle

android {
  defaultConfig {
          testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
      }
  testOptions {
          execution 'ANDROIDX_TEST_ORCHESTRATOR'
      }
}

dependencies {
    androidTestImplementation 'androidx.test:runner:1.1.1'
    androidTestUtil 'androidx.test:orchestrator:1.1.1'
}

Read More

Debugging

1. Set the debuggable variable (Some 3rd party dependencies might use this variable as well)

android {
    buildTypes {
        debug {
            debuggable true
        }
        release {
            debuggable false
        }
    }
}

2. Add breakpoints if needed (Click the Debug button instead of the Run button)

   • step over: go to next line of code
   • step into: go into the function

3. Add watchpoints for C/C++ code
   First thing first, install LLDB or LLDB navigator won't appear on Android Studio.
   Then debug C/C++ code as if debugging Java/Kotlin.

Read More

Test

To create modules in apps and publish which as individual APKs, you need Android Bundle

Android Bundle

Min SDK version: Android 5.0+ (API level 21)

Dynamic delivery: An android bundle, which contains features that you suppose the user won't use at install, is basically a bunch of code and resources. Users download bundles on demand.

APKs you will publish:

1. Base APK is where contains basic functionality and must-have resources at first download and install.
2. Configuration APKs are modules for specific screen density, CPU architecture or language. Google Play automatically generates configuration APKs for you.
3. (Optional) Dynamic feature APKs provide modularize features as the user requests

Read More

Getting started

1. Install Android Studio Canary 14
2. In AndroidManifest.xml

<application
    android:extractNativeLibs="false"
/>

3. In build.gradle

android {
    bundle {
        language {
            enableSplit = true
        }
        density {
            enableSplit = true
        }
        abi {
            enableSplit = true
        }
    }

        dependencies {
        // dynamic delivery
        implementation "com.google.android.play:core:${rootProject.ext.playcore}"
        // bundle's dependencies
        implementation 'com.android.support:customtabs:28.0.0'
    }

    // bundles
    dynamicFeatures = [":bbc_news"]
}

4. Create new Dynamic Feature Module (Edit -> New Module -> Dynamic Feature Module) and Fill in bbc_news as module name
5. Create NewsPageActivity in bbc_news module

public class NewsPageActivity extends AppCompatActivity {
    private final static String TAG = NewsPageActivity.class.getSimpleName();
    private final static String BBC_NEWS_URL = "https://www.bbc.com/news";
    private final static int CUSTOM_TABS_REQUEST_CODE = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_news_page);

        CustomTabsIntent customTabsIntent = new CustomTabsIntent.Builder()
                .setToolbarColor(getResources().getColor(R.color.colorPrimary))
                .build();
        customTabsIntent.intent.setData(Uri.parse(BBC_NEWS_URL));
        startActivityForResult(customTabsIntent.intent, CUSTOM_TABS_REQUEST_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == CUSTOM_TABS_REQUEST_CODE) {
            finish();
        }
    }
}

6. Update AndroidManifest.xml in bbc_news module

<application>
        <activity android:name=".NewsPageActivity">
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
            </intent-filter>
        </activity>
    </application>

7. Install and launch this bbc_news module See DynamicDeliveryActivity, bbc_news module

Code: DynamicDeliveryActivity, bbc_news module, tour_guide module, assets module, open_weather module
Google sample code
Read More

8. bundletool (Generate signed Android bundles)
   Before you publish your Android bundles and APK to Google Play, you need bundletool, a command line tool, to test those bundles locally.
   Download bundletool and move to AAD-Preparation/

• In Android Studio, go to Build -> Generate Signed Bundle/APK... -> generate a .aab file
• Generate a set of APKs

java -jar ../bundletool-all-0.9.0.jar build-apks --bundle=app/debug/app-debug.aab  --output=app/debug/MaterialDesign.apks

• Deploy APKs to a connected device

java -jar ../bundletool-all-0.9.0.jar install-apks --apks=app/debug/MaterialDesign.apks

• Unzip and see all APKs if you like

mkdir app/debug/apks
unzip app/debug/MaterialDesign.apks -d app/debug/apks

Sign APKs: apksigner
Sign .jar files, .aar files or Android bundles: jarsigner

Read more

Fundamentals of Tests

1. Tests give you rapid feedback on failures, which are spotted earlier on development cycle are far easier to fix than once that have gone live.
2. You are able to maintain a stable velocity throughout the lifetime of your project.
3. Avoid the boom bust cycle of crunch feature time and the aggregation of technical debt.

Testing pyramid

1. (small tests) Unit test
   • Validate the functionality and contracts of each class within your app
   • Run on your own local machine
   • fast and focus
   • 70%
2. (medium tests) Integration test
   • Interaction between a view and view model and run on particular screens, DAOs and multi-fragment tests
   • Run on real devices or emulators
   • 20%
3. (large tests) End-to-end test
   • validate end-to-end workflows that guide users through multiple modules and features
   • Run on real devices or emulators
   • 10%

Blog
Video

TDD, Test Driven Development

Principles of Unit Testing

1. Through: Test failure conditions, invalid inputs and boundary conditions.
2. Repeatable: Return the same results every time.
3. Focused: Focus one specific aspect of the code.
4. Verifies behaviour: Avoid writting too many assumption in the actual implementation of your code.
5. Fast
6. Concise

Device

You could run your unit tests on any of them:

1. Real devices
2. Emulator
3. Simulator. E.g. Roboletric

Robolectric supports testing on JVM-powered development machines

Instrumented test

Espresso

• NavigationDrawer unit test code
• Options menu unit test code

AndroidJUnit4

• RecyclerView unit test code

Robolectric

Mockito

Google sample Google testing blog
Google doc

Kotlin

The exam is only available in Java at this time (4/1/2019)
Read more

1. Basic Types
   • Bitwise operators
   • == vs ===
   • Numbers
   • Characters
   • Strings
   • Array
2. Control Flow
   • when
   • if
   • while
3. Returns and Jumps
   • break
   • xxx@ for or xxx@ while
   • return
4. Classes and Inheritance
   • Class with multiple constructors
   • Inheritance
   • interface
   • override
   • inner class
   • super@xxx.f()
   • abstract class
5. Properties and Fields
   • getter and setter
   • lateinit
   • ::
6. Visibility Modifiers
   • open
   • public
   • internal
   • protected
   • private
7. BaseClass, BaseClassExtensions
   • Extension functions
   • Extension properties
   • Companion objects (which is similar to static)
   • Call extension functions of the base class declared other class
   • Call functions both declared in the base class and self class inside extension functions (check BaseClassExtensions)
8. Data Class
   • Properties declared in the primary constructor or class body
   • Copying
   • E.g. User, Employee
9. Sealed Class, Enum Classes
   • enum vs sealed class
10. [Generics]
    • Declaration-site variance
    • Type projections
11. Nested and Inner Classes
    • Nested Class
    • Inner Class
    • Anonymous Inner Class [NOT YET]
12. Enum classes
    • Basic usage of enum classes
    • Another way to initialise the enum
    • Enum constants can also declare their own anonymous classes
    • Print all values of enum class
13. Objects
    • Object expressions - class
    • Object expressions - class + interface
    • Anonymous objects
    • Object declarations (Singleton)
    • Companion objects
14. Type aliases
    • Shorten types declaration
15. Inline classes
    • An inline class must have a single property initialised in the primary constructor
    • Inline classes cannot have properties with backing fields, ie, your code would be:

    val length: Int
      get() = s.length

    • Representation: Inline classes could be as inline, generic, interface or nullable
    • Inline classes vs type aliases
    • Enable inline classes in Gradle:

    compileKotlin {
        kotlinOptions.freeCompilerArgs += ["-XXLanguage:+InlineClasses"]
    }

16. Delegation

• Implementation by delegation
• by

// The last "b" (from ": Base by b") is implemented by the "b" in "Derived(b: Base)"
class Derived(b: Base) : Base by b

• Overriding functions and variables is optional

17. Delegated Properties

• Declare standard Delegates(Lazy, Observable and storing properties in a Map) via by
• Implement properties including standard delegates once for all
• Local delegated properties

18. Kotlin Singleton vs Java Singleton
19. Functions

• Basic functions
• Functions with default arguments
• Override functions
• Lambda
• variable number of arguments (vararg)
• Unit-returning functions
• infix fun

20. Projections

• in-projections
• out-projections
• star-projections

21. Higher-Order Functions and Lambdas

• Higher-Order Functions is a function that takes functions as parameters, or returns a function.
• Compare callbacks in Java and Kotlin (SAM for Kotlin classes)
• Lambda functions
• Pass functions as arguments to another function (this::func)
• Passing a lambda to the last parameter
• Implement a function type as an interface (You can either override invoke() or run invoke())
• invoke()
• ::

22. Inline Functions