给项目添加components

Architecture Components可以在谷歌的Maven仓库中找到，下面是使用步骤：

添加谷歌的Maven仓库

默认情况下，Android Studio的项目并没有配置谷歌的仓库，需要你打开项目的根build.gradle文件，然后手动添加，代码如下：

allprojects {
    repositories {
        jcenter()
        maven { url 'https://maven.google.com' }
    }
}

打开项目的build.gradle文件，添加你需要的依赖

Lifecycles
- implementation "android.arch.lifecycle:runtime:1.0.3" // not necessary if you are using lifecycle:extensions or lifecycle:common-java8
- annotationProcessor "android.arch.lifecycle:compiler:1.0.0" // not needed if you are using the DefaultLifecycleObserver from common-java8 artifact.
- 如果需要支持Java8, 添加:
  - implementation "android.arch.lifecycle:common-java8:1.0.0"
LiveData和ViewModel
- implementation "android.arch.lifecycle:extensions:1.0.0"
- 测试, 添加:
  - testImplementation "android.arch.core:core-testing:1.0.0"
- 使用 ReactiveStreams API, 添加:
  - implementation "android.arch.lifecycle:reactivestreams:1.0.0"
Room
- implementation "android.arch.persistence.room:runtime:1.0.0"
- annotationProcessor "android.arch.persistence.room:compiler:1.0.0"
- 测试 Room migrations, 添加:
  - testImplementation "android.arch.persistence.room:testing:1.0.0"
- RxJava支持, 添加:
  - implementation "android.arch.persistence.room:rxjava2:1.0.0"
Paging
- implementation "android.arch.paging:runtime:1.0.0-alpha3"