[AppdevCon '19] Demystifying Android Libraries

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OSS Android libraries developed 2

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How does Gradle process Android Libraries @nisrulz 3

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How does Gradle process Android Libraries repositories { jCenter() } dependencies { implementation 'com.github.nisrulz:awesomelib:1.0' ... } 4 @nisrulz

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How does Gradle process Android Libraries repositories { jCenter() } dependencies { implementation 'com.github.nisrulz:awesomelib:1.0' ... } 5 @nisrulz // Dependency Notation

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How does Gradle process Android Libraries repositories { jCenter() } dependencies { implementation 'com/github/nisrulz/awesomelib/1.0' ... } 6 @nisrulz

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How does Gradle process Android Libraries implementation 'com.github.nisrulz:awesomelib:1.0' 7 @nisrulz

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How does Gradle process Android Libraries implementation 'com/github/nisrulz/awesomelib/1.0' 8 @nisrulz

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How does Gradle process Android Libraries implementation 'com/github/nisrulz/awesomelib/1.0' 9 @nisrulz

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How does Gradle process Android Libraries implementation 'com/github/nisrulz/awesomelib/1.0' 10 @nisrulz

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How does Gradle process Android Libraries implementation 'com.github.nisrulz:awesomelib:1.0' 11 @nisrulz

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Android ARchive(AAR) @nisrulz 12

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13 @nisrulz

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14 @nisrulz

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AAR = Java ARchive(JAR) + Resources 15 @nisrulz

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AAR = Java ARchive(JAR) + Resources Sensey: https://github.com/nisrulz/sensey 16 @nisrulz

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AAR = Java ARchive(JAR) + Resources @nisrulz 17

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Sensey’s build.gradle dependencies { ... // Other testing dependencies // Transitive dependency: Support Compat library implementation "com.android.support:support-compat:27.0.2" } 18 @nisrulz

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Using AAR as dependency @nisrulz 19

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Using an AAR as dependency repositories{ flatDir{ dirs 'libs' } } dependencies { implementation(name:'nameOfYourAARFileWithoutExtension', ext:'aar') } @nisrulz 20

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Using an AAR as dependency repositories{ flatDir{ dirs 'libs' } } dependencies { implementation(name:'nameOfYourAARFileWithoutExtension', ext:'aar') } // No transitive dependencies of the library are downloaded 21 @nisrulz

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Why doesn’t my AAR download transitive dependencies? @nisrulz 22

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Sensey’s AAR 23 @nisrulz

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Sensey’s AAR No build.gradle file 24 @nisrulz

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Maven Artifact 25 @nisrulz

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Maven Artifact 26 @nisrulz

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POM? 27 @nisrulz

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POM ● Project Object Model ● XML file ● Configuration details used by Maven to build the project 28 @nisrulz

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POM POM of Sensey Android Library 4.0.0 com.github.nisrulzsensey1.8.0 aarsensey Android library which makes playing with sensor events & detecting gestures a breeze. https://github.com/nisrulz/sensey The Apache Software License, Version 2.0http://www.apache.org/licenses/LICENSE-2.0.txt nisrulzNishant Srivastavanisrulz@gmail.com https://github.com/nisrulz/sensey.git https://github.com/nisrulz/sensey.git https://github.com/nisrulz/sensey com.android.support support-compat27.0.2 runtime ... 29 @nisrulz

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POM POM of Sensey Android Library ... com.android.support support-compat27.0.2 runtime ... 31 @nisrulz

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Bundled Proguard Configs 32 @nisrulz

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Bundled Proguard Configs android { release { minifyEnabled true // Rules to be used during the AAR generation proguardFiles 'proguard-rules-for-building-library.pro' } ... } 33 @nisrulz

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Bundled Proguard Configs android { release { minifyEnabled true // Rules to be used during the AAR generation proguardFiles 'proguard-rules-for-building-library.pro' // Rules appended to the integrating app consumerProguardFiles 'proguard-rules-for-using-library.pro' } ... } 34 @nisrulz

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Bundled Proguard Configs 35 @nisrulz

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Bundled Proguard Configs 36 @nisrulz

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Bundled Proguard Configs # Fuel’s bundled Proguard file # Without specifically keeping this class, # callbacks on android don't function properly. -keep class com.github.kittinunf.fuel.android.util.AndroidEnvironment 37 @nisrulz

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Bundled Proguard Configs # DON'T DO THIS # Do not obfuscate the input class files -dontobfuscate # Optimizes variable allocation on the local variable frame. -optimizations !code/allocation/variable # Preserved as entry points -keep public class * { public protected *; } 38 @nisrulz

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Bundled Proguard Configs # DON'T DO THIS # Adding the below in library proguard rules disables # the optimizations in the Android app -dontoptimize 39 @nisrulz

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Bundled Proguard Configs # To check the merged configuration # Add the below to your app’s current proguard rules -printconfiguration proguard-merged-config.txt 40 @nisrulz

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Bundled Proguard Configs 41 @nisrulz

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Modularization 42 @nisrulz

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Modularization 43 @nisrulz

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Modularization EasyDeviceInfo: https://github.com/nisrulz/easydeviceinfo 44 @nisrulz

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Modularization dependencies { def libVer = {latest_version} // Base + Ads Bundled Library implementation "com.github.nisrulz:easydeviceinfo:$libVer" // Base Library implementation "com.github.nisrulz:easydeviceinfo-base:$libVer" // Ads Library implementation "com.github.nisrulz:easydeviceinfo-ads:$libVer" } 45 @nisrulz

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Modularization ... com.github.nisrulz easydeviceinfo-ads 2.5.0 compile com.github.nisrulz easydeviceinfo-base 2.5.0 compile ... 46 @nisrulz

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Modularization ... com.github.nisrulz easydeviceinfo-ads 2.5.0 compile com.github.nisrulz easydeviceinfo-base 2.5.0 compile ... 47 @nisrulz

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Modularization ... com.github.nisrulz easydeviceinfo-ads 2.5.0 compile com.github.nisrulz easydeviceinfo-base 2.5.0 compile ... 48 @nisrulz

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Modularization ... com.github.nisrulz easydeviceinfo-common2.5.0 compile com.google.android.gms play-services-ads-identifier16.0.0 runtime ... 49 @nisrulz

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Modularization ... com.github.nisrulz easydeviceinfo-common2.5.0 compile com.google.android.gms play-services-ads-identifier16.0.0 runtime ... 50 @nisrulz

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Avoiding Resource Name Conflicts 51 @nisrulz

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Conflict occurs between a library & app resource > Project will not compile What happens when... 52 @nisrulz

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Conflict occurs between 2 libraries integrated in the app > Resources from library defined first in build.gradle gets included What happens when... 53 @nisrulz

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Solution? 54 @nisrulz

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Add a prefix to all your resources. Solution? 55 @nisrulz

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Add a prefix to all your resources. How? Solution? 56 @nisrulz

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Add a prefix to all your resources. How? ● Enforce this in Android Studio Solution? 57 @nisrulz

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Add a prefix to all your resources. How? ● Enforce this in Android Studio ● Declare in build.gradle of library android { resourcePrefix 'YOUR_PREFIX_' // i.e 'sensey_' } Solution? 58 @nisrulz

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Solution? Resource named ‘app_name’ does not start with the project’s resource prefix ‘sensey_’; Rename to `sensey_app_name`? 59 @nisrulz

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minSdkVersion Restriction 60 @nisrulz

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minSdkVersion of app >= minSdkVersion of library minSdk Restriction 61 @nisrulz

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minSdk Restriction 62 @nisrulz

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Manifest merger failed : uses-sdk:minSdkVersion 14 cannot be smaller than version 21 declared in library [:sensey] Suggestion: + Use a compatible library with a minSdk of at most 14 + Increase this project's minSdk version to at least 21 + Use tools:overrideLibrary="com.github.nisrulz.sensey" to force usage (may lead to runtime failures) minSdk Restriction 63 @nisrulz

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... minSdk Restriction 66 @nisrulz

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... minSdk Restriction 67 @nisrulz

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Access Visibility vs Code Organization 68 @nisrulz

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Visibility vs Organization 69 @nisrulz

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Visibility vs Organization ● Code organized in individual packages; everything is public 70 @nisrulz

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Visibility vs Organization ● Code organized inside one package; Classes and methods are package private and only public on demand 71 @nisrulz

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Visibility vs Organization ● Code organized inside the module i.e individual packages Classes and methods are internal and only public on demand (in Kotlin land) 72 @nisrulz

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Visibility vs Organization ● internal and only public on demand (in Kotlin land) 73 @nisrulz

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Visibility vs Organization ● Code organized inside the module i.e individual packages Classes and methods are internal and only public on demand (in Kotlin land) ● Drawback ○ Need dependency on kotlin std library 74 @nisrulz

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Lifecycle-Aware Android Library 75 @nisrulz

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Lifecycle Components Classes designed to help deal with Android lifecycle ● Lifecycle ● LifecycleOwner ● LifecycleObserver 76 @nisrulz

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Lifecycle Owner 77 @nisrulz

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Lifecycle Owner + Lifecycle 78 @nisrulz

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Lifecycle Owner + Lifecycle ● ● ● ● 79 @nisrulz

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Lifecycle Owner + Lifecycle class MainActivity extends AppCompatActivity() {...} 80 @nisrulz

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Lifecycle Owner + Lifecycle class MainActivity extends AppCompatActivity() {...} public class AppCompatActivity extends FragmentActivity{...} 81 @nisrulz

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Lifecycle Owner + Lifecycle class MainActivity extends AppCompatActivity() {...} public class AppCompatActivity extends FragmentActivity{...} public class FragmentActivity extends SupportActivity {...} public class SupportActivity extends Activity implements LifecycleOwner, Component { ... public Lifecycle getLifecycle() {return this.mLifecycleRegistry();} ... } 83 @nisrulz

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Lifecycle Observer 85 @nisrulz

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Lifecycle Observer 86 @nisrulz

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LifecycleObserver dependencies { def lifecycleVer = "2.0.0" // Runtime implementation "androidx.lifecycle:lifecycle-runtime:$lifecycleVer" // Annotation Support annotationProcessor "androidx.lifecycle:lifecycle-compiler:$lifecycleVer" ... } 87 @nisrulz

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LifecycleObserver public class AwesomeLib implements LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_CREATE) public void init() { ... } @OnLifecycleEvent(Lifecycle.Event.ON_START) public void libOnStart() { ... } ... @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) public void cleanup() { ... } } 88 @nisrulz

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LifecycleOwner class MainActivity : AppCompatActivity() { val awesomeLib = AwesomeLib() override fun onStart() { ... // Add lifecycle observer lifecycle.addObserver(awesomeLib) } override fun onStop() { ... // Remove lifecycle observer lifecycle.removeObserver(awesomeLib) } } 89 @nisrulz

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LifecycleAware Library 90 @nisrulz

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ProcessLifecycleOwner Class that tracks the lifecycle of whole application process 91 @nisrulz

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ProcessLifecycleOwner dependencies { // For ProcessLifecycleOwner implementation "androidx.lifecycle:lifecycle-extensions:2.0.0" ... } 92 @nisrulz

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ProcessLifecycleOwner Does something weird… 93 @nisrulz

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ProcessLifecycleOwner Does something weird… Adding lifecycle-extensions artifact > automatically adds element to the merged manifest 94 @nisrulz

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ProcessLifecycleOwner 95 @nisrulz

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ProcessLifecycleOwner ... 96 @nisrulz

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ProcessLifecycleOwner ... 97 @nisrulz

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ProcessLifecycleOwner ... 98 @nisrulz Pre-AndroidX

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ProcessLifecycleOwner ... 99 @nisrulz Pre-AndroidX

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ProcessLifecycleOwner 100 @nisrulz Pre-AndroidX

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ProcessLifecycleOwner ... 101 @nisrulz AndroidX

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ProcessLifecycleOwner ... 102 @nisrulz AndroidX

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ProcessLifecycleOwner // Internal class to initialize Lifecycles. public class ProcessLifecycleOwnerInitializer extends ContentProvider { @Override public boolean onCreate() { ... ProcessLifecycleOwner.init(getContext()); return true; } ... } 103 @nisrulz

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ProcessLifecycleOwner Why? To invoke ProcessLifecycleOwner as soon as process starts 104 @nisrulz

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ProcessLifecycleOwner Why? To invoke ProcessLifecycleOwner as soon as process starts Drawback? Initializes ProcessLifecycleOwner even if your app does not use it! 105 @nisrulz

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ProcessLifecycleOwner How to get rid of it in app? 106 @nisrulz

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ProcessLifecycleOwner How to get rid of it in app? Use Merge rule marker in app’s AndroidManifest.xml: // Remove marked element from the merged manifest tools:node="remove" 107 @nisrulz

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ProcessLifecycleOwner ... 108 @nisrulz App’s AndroidManifest.xml

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ProcessLifecycleOwner ... 109 @nisrulz App’s AndroidManifest.xml

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ProcessLifecycleOwner ... 110 @nisrulz App’s AndroidManifest.xml

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ProcessLifecycleOwner ... 111 @nisrulz App’s AndroidManifest.xml

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Auto Initialize Android Library 112 @nisrulz

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AutoInit Android Library Android Libraries need Android context to handle simple tasks such as ● Hook into Android Runtime ● Access app resources ● Use System Services ● Register BroadcastReceiver 113 @nisrulz

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AutoInit Android Library public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); // Init android library AwesomeLib.getInstance().init(this); } } 114 @nisrulz

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AutoInit Android Library 117 @nisrulz

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AutoInit Android Library 118 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. 119 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. Simply because ContentProvider ● Is created and initialized (on the main thread) before all other components ● Participate in manifest merging at build time. 120 @nisrulz

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AutoInit Android Library public class AwesomeLibInitProvider extends ContentProvider { ... @Override public boolean onCreate() { // get the context (Application context) Context context = getContext(); // initialize AwesomeLib here AwesomeLib.getInstance().init(context); return false; } ... } 121 @nisrulz

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AutoInit Android Library 123 @nisrulz

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AutoInit Android Library 124 @nisrulz

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AutoInit Android Library 125 @nisrulz

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AutoInit Android Library 126 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. 127 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. Challenges: ● There can be only one Content Provider with a given “authority” string ● Only run on main thread 128 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. 129 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. Why this is a bad idea: ● Increases startup time ● Bloats applications even when not used ● Abusing functionality of ContentProvider 130 @nisrulz

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AutoInit Android Library ContentProvider can be used to simplify the process. Why this is a bad idea: ● Increases startup time (Solution: async initialize) ● Bloats applications even when not used ● Abusing functionality of ContentProvider 131 @nisrulz

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AutoInit Android Library Some android libraries that use this... 132 @nisrulz

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AutoInit Android Library ProcessLifecycleOwner [androidx.lifecycle:lifecycle-extensions:2.0.0] 133 @nisrulz

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AutoInit Android Library Firebase [com.google.firebase:firebase-common:16.0.5] 134 @nisrulz

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AutoInit Android Library Facebook-Core [com.facebook.android:facebook-core:4.34.0] 135 @nisrulz

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AutoInit Android Library Facebook-Marketing [com.facebook.android:facebook-marketing:4.34.0] 136 @nisrulz

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AutoInit Android Library Crashlytics [com.crashlytics.sdk.android:crashlytics:2.9.5] 137 @nisrulz

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AutoInit Android Library Picasso // Pre - v2.71828 Picasso.with(this).load("......").into(imageView); // After - v2.71828 Picasso.get().load("......").into(imageView); 138 @nisrulz

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AutoInit Android Library Picasso // Pre - v2.71828 Picasso.with(this).load("......").into(imageView); // After - v2.71828 Picasso.get().load("......").into(imageView); 139 @nisrulz

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AutoInit Android Library Picasso [com.squareup.picasso:picasso:2.71828] 140 @nisrulz

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Links/References Android Libraries I have built: https://github.com/nisrulz/nisrulz.github.io#open-source-co ntributions Auto initialize android library example: https://github.com/nisrulz/android-examples/tree/develop/Au toInitLibrary Lifecycle Aware android library example: https://github.com/nisrulz/android-examples/tree/develop/Li feCycleCompForLib 141 @nisrulz