Android JetPack

Google 在 2018 Google I/O 大会上推出了 Android Jetpack，它包含了开发库、 工具 以及最佳实践指南。

Jetpack 是背包式飞行器的意思，是一种小巧的个人飞行器。顾名思义，通过使用Android Jetpack 这套组件，可以帮助开发者更高效、更容易地构建优秀的应用。为此，Android 官方团队也把 Jetpack 的Logo 设计成了一个背着火箭的小机器人。

除了在 2018 Google I/O 大会上新添加的功能外，它还把以前退出的一些功能囊括其中，比如 Architecture Components 等。并且，Android 团队将继续在Android平台上为 Jetpack 添加新的功能。

下面来看一下 Jetpack 包含了哪些功能，下图会随着 Jetpack 功能的更新保持同步更新：

关于AndroidX

先来个插曲介绍一下 AndroidX，后面 Android 会把 support 库放到 AndroidX 中，仅仅会改变包名和 Maven 库的名字，类的名字不会改变。

添加依赖汇总

官方文档

添加 Google Maven 仓库

在project下的build.gradle中添加Maven仓库

allprojects {
    repositories {
        jcenter()
        google()//添加Google Maven仓库
    }
}

添加依赖

LifeCycle

包含 LiveData 和 ViewModel 的依赖。

Android X

dependencies {
    def lifecycle_version = "2.0.0"

    // ViewModel and LiveData
    implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
    // alternatively - just ViewModel
    implementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version" // use -ktx for Kotlin
    // alternatively - just LiveData
    implementation "androidx.lifecycle:lifecycle-livedata:$lifecycle_version"
    // alternatively - Lifecycles only (no ViewModel or LiveData). Some UI
    //     AndroidX libraries use this lightweight import for Lifecycle
    implementation "androidx.lifecycle:lifecycle-runtime:$lifecycle_version"

    annotationProcessor "androidx.lifecycle:lifecycle-compiler:$lifecycle_version" // use kapt for Kotlin
    // alternately - if using Java8, use the following instead of lifecycle-compiler
    implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"

    // optional - ReactiveStreams support for LiveData
    implementation "androidx.lifecycle:lifecycle-reactivestreams:$lifecycle_version" // use -ktx for Kotlin

    // optional - Test helpers for LiveData
    testImplementation "androidx.arch.core:core-testing:$lifecycle_version"
}

AndroidX 之前版本

dependencies {
    def lifecycle_version = "1.1.1"

    // ViewModel and LiveData
    implementation "android.arch.lifecycle:extensions:$lifecycle_version"
    // alternatively - just ViewModel
    implementation "android.arch.lifecycle:viewmodel:$lifecycle_version" // use -ktx for Kotlin
    // alternatively - just LiveData
    implementation "android.arch.lifecycle:livedata:$lifecycle_version"
    // alternatively - Lifecycles only (no ViewModel or LiveData).
    //     Support library depends on this lightweight import
    implementation "android.arch.lifecycle:runtime:$lifecycle_version"

    annotationProcessor "android.arch.lifecycle:compiler:$lifecycle_version" // use kapt for Kotlin
    // alternately - if using Java8, use the following instead of compiler
    // 比如你想使用 DefaultLifecycleObserver 就要依赖  java 8
    implementation "android.arch.lifecycle:common-java8:$lifecycle_version"

    // optional - ReactiveStreams support for LiveData
    implementation "android.arch.lifecycle:reactivestreams:$lifecycle_version"

    // optional - Test helpers for LiveData
    testImplementation "android.arch.core:core-testing:$lifecycle_version"
}

Room

AndroidX

dependencies {
    def room_version = "2.1.0-alpha03"

    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version" // use kapt for Kotlin

    // optional - RxJava support for Room
    implementation "androidx.room:room-rxjava2:$room_version"

    // optional - Guava support for Room, including Optional and ListenableFuture
    implementation "androidx.room:room-guava:$room_version"

    // optional - Coroutines support for Room
    implementation "androidx.room:room-coroutines:$room_version"

    // Test helpers
    testImplementation "androidx.room:room-testing:$room_version"
}

AndroidX 之前版本

dependencies {
    def room_version = "1.1.1"

    implementation "android.arch.persistence.room:runtime:$room_version"
    annotationProcessor "android.arch.persistence.room:compiler:$room_version" // use kapt for Kotlin

    // optional - RxJava support for Room
    implementation "android.arch.persistence.room:rxjava2:$room_version"

    // optional - Guava support for Room, including Optional and ListenableFuture
    implementation "android.arch.persistence.room:guava:$room_version"

    // Test helpers
    testImplementation "android.arch.persistence.room:testing:$room_version"
}

dependencies {
    // ViewModel and LiveData
    implementation "android.arch.lifecycle:extensions:1.1.1"
    // alternatively, just ViewModel
    implementation "android.arch.lifecycle:viewmodel:1.1.1"
    // alternatively, just LiveData
    implementation "android.arch.lifecycle:livedata:1.1.1"
 
    annotationProcessor "android.arch.lifecycle:compiler:1.1.1"
 
    // Room (use 1.1.0-beta3 for latest beta)
    implementation "android.arch.persistence.room:runtime:1.0.0"
    annotationProcessor "android.arch.persistence.room:compiler:1.0.0"
 
    // Paging
    implementation "android.arch.paging:runtime:1.0.0-rc1"
 
    // Test helpers for LiveData
    testImplementation "android.arch.core:core-testing:1.1.1"
 
    // Test helpers for Room
    testImplementation "android.arch.persistence.room:testing:1.0.0"
}