Using the Retrolambda library. This tutorial explains the usage of the Retrolambda library.
1. Retrolambda
Retrolambda is a library which allows to use Java 8 lambda expressions, method references and try-with-resources statements on Java 7, 6 or 5.
The Gradle Retrolambda Plug-in allows to integrate Retrolambda into a Gradle based build. This allows for example to use these constructs in an Android application, as standard Android development currently does not yet support Java 8.
2. Exercise: Using Retrolambda in your Android project
2.1. Create project
Create a new Android project with the top level project name
com.vogella.android.retrolambda. Add a button to the existing layout with the
@+id/button"
ID.
2.2. Add Retrolambda to your Gradle build configuratoin
Add the me.tatarka:gradle-retrolambda plug-in as dependency to your build.gradle file.
buildscript {
repositories {
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:1.4.0'
classpath 'me.tatarka:gradle-retrolambda:3.2.0'
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
}Add the source and target compatibility to Java 8 and apply the new plug-in in your
app/build.gradle file.
apply plugin: 'com.android.application'
apply plugin: 'me.tatarka.retrolambda'
android {
compileSdkVersion 22
buildToolsVersion "23.0.0 rc2"
defaultConfig {
applicationId "com.vogella.android.retrolambda"
minSdkVersion 22
targetSdkVersion 22
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
}2.3. Validate setup by using a lambda expressions
Using the lambda configuration by using it with your button to show a Toast once the button is clicked.
package com.vogella.android.retrolambda;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button view = (Button) findViewById(R.id.button);
view.setOnClickListener(e-> Toast.makeText(this,"Hello", Toast.LENGTH_LONG).show());
}
}3. Retrofit resources
3.1. vogella Java example code
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