Android 之 Jetpack - Lifecycle

1. 添加依赖（app/build.gradle.kts）

dependencies {val lifecycleVersion = "2.8.0"implementation("androidx.lifecycle:lifecycle-runtime-ktx:$lifecycleVersion")implementation("androidx.lifecycle:lifecycle-common-java8:$lifecycleVersion")
}

注​​：Kotlin 项目需启用 kotlin-kapt插件支持注解处理

2. 创建 LifecycleObserver（两种实现方式）

​​方式一：继承 DefaultLifecycleObserver（官方推荐）

import androidx.lifecycle.DefaultLifecycleObserver
import androidx.lifecycle.LifecycleOwner
import android.util.Logclass CustomLifecycleObserver : DefaultLifecycleObserver {private val TAG = "LifecycleObserver"override fun onCreate(owner: LifecycleOwner) {Log.d(TAG, "onCreate - State: ${owner.lifecycle.currentState}")}override fun onStart(owner: LifecycleOwner) {Log.d(TAG, "onStart - State: ${owner.lifecycle.currentState}")}override fun onResume(owner: LifecycleOwner) {Log.d(TAG, "onResume - State: ${owner.lifecycle.currentState}")}override fun onPause(owner: LifecycleOwner) {Log.d(TAG, "onPause - State: ${owner.lifecycle.currentState}")}override fun onDestroy(owner: LifecycleOwner) {Log.d(TAG, "onDestroy - State: ${owner.lifecycle.currentState}")}
}

方式二：使用注解（旧版兼容）

import androidx.lifecycle.LifecycleObserver
import androidx.lifecycle.OnLifecycleEvent
import androidx.lifecycle.Lifecycle
import android.util.Logclass AnnotationLifecycleObserver : LifecycleObserver {private val TAG = "AnnotationObserver"@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)fun setupResources() {Log.d(TAG, "Resources initialized")}@OnLifecycleEvent(Lifecycle.Event.ON_STOP)fun releaseResources() {Log.d(TAG, "Resources released")}
}

3. 在 Activity 中注册观察者

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.lifecycle.Lifecycleclass MainActivity : AppCompatActivity() {override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_main)// 注册两种观察者lifecycle.addObserver(CustomLifecycleObserver())lifecycle.addObserver(AnnotationLifecycleObserver())// 实时打印当前生命周期状态（验证状态变化）Log.d("MainActivity", "Current State: ${lifecycle.currentState}") // 输出：CREATED}override fun onResume() {super.onResume()Log.d("MainActivity", "Current State: ${lifecycle.currentState}") // 输出：RESUMED}
}

4. 生命周期状态与事件关系

Lifecycle 的 ​​5 种状态​​与 ​​7 种事件​​映射关系：