[Devoxx Belgium '18] Things I wish I knew when I started building Android Libraries/SDK -Vol.2

View Slide

OSS Android libraries developed

View Slide

Android ARchive(AAR)
@nisrulz

View Slide

AAR = Java ARchive(JAR) + Resources
@nisrulz

View Slide

@nisrulz
Sensey: https://github.com/nisrulz/sensey

View Slide

@nisrulz

View Slide

Using an AAR as dependency
@nisrulz

View Slide

@nisrulz
repositories{
flatDir{
dirs 'libs'
}
}
dependencies {
implementation(name:'nameOfYourAARFileWithoutExtension', ext:'aar')
}

View Slide

@nisrulz
repositories{
flatDir{
dirs 'libs'
}
}
dependencies {
implementation(name:'nameOfYourAARFileWithoutExtension', ext:'aar')
}
// None of the dependencies of the library are downloaded

View Slide

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

View Slide

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

View Slide

Sensey’s AAR
@nisrulz

View Slide

Sensey’s AAR
@nisrulz
No build.gradle file

View Slide

Maven Artifact
@nisrulz

View Slide

@nisrulz
Maven Artifact

View Slide

POM?
@nisrulz

View Slide

POM
@nisrulz
+ Stands for Project Object Model
+ Is a XML file
+ Contains
+ Information about the project
+ Configuration details used by Maven to build the project

View Slide

POM
@nisrulz
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 [email protected]

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

...

View Slide

POM
@nisrulz
POM of Sensey Android Library

...

com.android.support
support-compat27.0.2
runtime

...

View Slide

Bundled Proguard Configs
@nisrulz

View Slide

@nisrulz
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'
}
...
}

View Slide

@nisrulz
Fuel: https://github.com/kittinunf/Fuel

View Slide

@nisrulz

View Slide

@nisrulz
# 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

View Slide

@nisrulz
# To check the merged configuration
# Add the below to your current config
-printconfiguration proguard-merged-config.txt

View Slide

@nisrulz
# DON'T DO THIS
-dontobfuscate
-optimizations !code/allocation/variable
# Effectively no optimizations
-keep public class * {
public protected *;
}

View Slide

@nisrulz
# DON'T DO THIS
# Adding the below in library proguard rules disables
# the optimizations in the Android app
-dontoptimze

View Slide

Modularization
@nisrulz

View Slide

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

View Slide

Modularization
@nisrulz
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"
}

View Slide

Modularization
@nisrulz

...

com.github.nisrulz
easydeviceinfo-ads 2.4.1
compile

com.github.nisrulz
easydeviceinfo-base 2.4.1
compile

...

View Slide

Modularization
@nisrulz

...

com.github.nisrulz
easydeviceinfo-common2.4.1
compile

com.google.android.gms
play-services-basement11.8.0
runtime

...

View Slide

Avoiding Resource Name
Conflicts
@nisrulz

View Slide

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

View Slide

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

View Slide

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

View Slide

@nisrulz
Add a prefix to all your resources.
Enforce this in Android Studio
android {
resourcePrefix 'YOUR_PREFIX_' // i.e 'sensey_'
}
Solution?

View Slide

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

View Slide

minSdkVersion Restriction
@nisrulz

View Slide

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

View Slide

@nisrulz
minSdk Restriction

View Slide

@nisrulz
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

View Slide

@nisrulz
xmlns:tools="http://schemas.android.com/tools"
package="com.github.nisrulz.senseysample">

...

minSdk Restriction

View Slide

Access Visibility
vs
Code Organization
@nisrulz

View Slide

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

View Slide

@nisrulz
+ Code organized inside one package; everything is package private
and only public on demand

View Slide

@nisrulz
+ Code organized inside one package; everything is package private
and only public on demand
But if in Kotlin land,
+ Code organized in individual packages; everything is internal and
only public on demand

View Slide

@nisrulz
// file name: exampleLibrary.kt
// module name: example
package com.example.library

View Slide

@nisrulz
// visible inside exampleLibrary.kt
private fun setup() { ... }

View Slide

@nisrulz
// property is visible everywhere
public var name: String = "ExampleLib"
// setter is visible only in exampleLibrary.kt
private set{...}

View Slide

@nisrulz
// property is visible everywhere
public var name: String = "ExampleLib"
// setter is visible only in exampleLibrary.kt
private set{...}
// visible inside the module i.e example
internal val debugTag = "Example-Debug"

View Slide

Lifecycle-Aware
Android Library
@nisrulz

View Slide

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

View Slide

@nisrulz
lifecycle

View Slide

@nisrulz
lifecycle
i.e Activity, Fragment, Service, Custom

View Slide

LifecycleObserver
@nisrulz
dependencies {
def lifecycleVer = "1.1.1"
// Runtime
implementation "android.arch.lifecycle:runtime:$lifecycleVer"
// Annotation Support
annotationProcessor "android.arch.lifecycle:compiler:$lifecycleVer"
...
}

View Slide

LifecycleObserver
@nisrulz
object AwesomeLibrary : LifecycleObserver {
@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
fun init() { ... }
@OnLifecycleEvent(Lifecycle.Event.ON_START)
fun onStart() { ... }
...
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
fun cleanup() { ...}
}

View Slide

LifecycleOwner
@nisrulz
class MainActivity : AppCompatActivity() { // LifecycleOwner
override fun onResume() {
// Add lifecycle observer
lifecycle.addObserver(AwesomeLibrary.INSTANCE)
}
override fun onStop() {
// Remove lifecycle observer
lifecycle.removeObserver(AwesomeLibrary.INSTANCE)
}
}

View Slide

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

View Slide

@nisrulz
dependencies {
def lifecycleVer = "1.1.1"
// For ProcessLifecycleOwner
implementation "android.arch.lifecycle:extensions:$lifecycleVer"
...
}

View Slide

@nisrulz
extension artifact automatically adds
element to your manifest

View Slide

@nisrulz

...
android:name="android.arch.lifecycle.ProcessLifecycleOwnerInitializer"
android:authorities="com.example.app.lifecycle-trojan"
android:exported="false"
android:multiprocess="true" />

View Slide

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

View Slide

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

View Slide

Auto Initialize
Android Library
@nisrulz

View Slide

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

View Slide

@nisrulz
public class MyApplication extends Application {
@Override
public void onCreate() {
super.onCreate();
// Init android library
MyAwesomeLibrary.init(this);
}
}

View Slide

@nisrulz
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:name=".MyApplication"
... >

View Slide

@nisrulz
ContentProvider “can be” used to simplify the process.
How? ContentProvider is
+ Created and initialized (on the main thread) before
all other components
+ Participate in manifest merging at build time.

View Slide

@nisrulz
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;
}
...
}

View Slide

@nisrulz
package="github.nisrulz.sample.awesomelib">

android:name=".AwesomeLibInitProvider"
android:authorities="${applicationId}.awesomelibinitprovider"
android:enabled="true"
android:exported="false">

View Slide

@nisrulz
ContentProvider “can be” used to simplify the process.
Why it shouldn’t be
+ There can be only one Content Provider with a given
“authority” string
+ Only run on main thread; does not support multi
process

View Slide

Links/References
@nisrulz
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

View Slide

twitter.com/nisrulz
github.com/nisrulz
www.nisrulz.com

View Slide

[Devoxx Belgium '18] Things I wish I knew when I started building Android Libraries/SDK -Vol.2

[Devoxx Belgium '18] Things I wish I knew when I started building Android Libraries/SDK -Vol.2

Nishant Srivastava

More Decks by Nishant Srivastava

Other Decks in Technology

Featured

Transcript