Android ProcessLifecycleOwner 观察进程生命周期

简介

ProcessLifecycleOwner 直译，就是，进程生命周期所有者。
通过 DOC 注释了解到：

1. Lifecycle.Event.ON_CREAT 事件 在进程启动后，会收到一次；
2. Lifecycle.Event.ON_DESTROY 事件，永远不会收到；
3. 首个 activity 的 onStart , onResume 后，owner 会收到 同类型的事件 Lifecycle.Event.ON_START, Lifecycle.Event.ON_RESUM；
4. 最后的 Activity 的 onPause、onStop 后， owner 会收到 同类型事件Lifecycle.Event.ON_PAUSE, Lifecycle.Event.ON_STOP (系统保证了收到的事件是正常的，不会在配置更改而销毁和重新创建活动时发送这样的事件)

用于判断进程前后台很方便

其本身是个单例实现，源码:

@NonNull
public static LifecycleOwner get() {return sInstance;
}

---

使用

依赖

api "androidx.lifecycle:lifecycle-process:2.5.1"

用法1，结合 LiveData

数据变化的观察，将依赖于 进程的活动事件

liveData.observe(ProcessLifecycleOwner.get(), Observer {when (ProcessLifecycleOwner.get().lifecycle.currentState) {Lifecycle.State.STARTED, Lifecycle.State.RESUMED, Lifecycle.State.CREATED -> {...}else -> {}}
})

要注意的是，Lifecycle.State 和 Lifecycle.Event 内的常量不是一一对应的

用法2，获取 owner的 lifecycle 实例，并对 lifecycle 添加观察者

ProcessLifecycleOwner.get().lifecycle.addObserver(LifecycleObserver observer) 

查看 LifecycleObserver 的 DOC 注释，建议不要直接使用该类；而是使用其子类 DefaultLifecycleObserver 或 LifecycleEventObserver

示例(可用于判断进程前后台)：

ProcessLifecycleOwner.get().lifecycle.addObserver(object: DefaultLifecycleObserver {override fun onCreate(owner: LifecycleOwner) {super.onCreate(owner)}override fun onStart(owner: LifecycleOwner) {super.onStart(owner)}override fun onResume(owner: LifecycleOwner) { // 应用前台super.onResume(owner)}override fun onPause(owner: LifecycleOwner) { // 应用后台super.onPause(owner)}override fun onStop(owner: LifecycleOwner) {super.onStop(owner)}override fun onDestroy(owner: LifecycleOwner) {super.onDestroy(owner)}
})ProcessLifecycleOwner.get().lifecycle.addObserver(object: LifecycleEventObserver {override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {when (event) {Lifecycle.Event.ON_START -> {Log.e("ProcessLifecycleOwner", "ON_START")}Lifecycle.Event.ON_RESUME -> { // 应用前台Log.e("ProcessLifecycleOwner", "ON_RESUME")}Lifecycle.Event.ON_PAUSE -> { // 应用后台Log.e("ProcessLifecycleOwner", "ON_PAUSE")}Lifecycle.Event.ON_STOP -> {Log.e("ProcessLifecycleOwner", "ON_STOP")}else -> {}}}
})