四大组件:Activity生命周期Android12

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  Activity 类是 Android 应用的关键组件&＃xff0c;而 Activity 的启动和组合方式则是该平台应用模型的基本组成部分。在java编程范式中&＃xff0c;应用是通过 main() 方法启动的&＃xff0c;而 Android 系统与此不同&＃xff0c;它会调用与其生命周期特定阶段相对应的特定回调方法来启动 Activity 实例中的代码。

1. Activity生命周期

1.1 Activity生命周期方法说明

android官网 了解 Activity 生命周期

1.2 Activity.java流程源码对照

AMS:startActivity桌面启动应用、应用内部启动startActivity-Android12、Activity相关初始化-Android12

• Activity -- Instrumentation -- AMS/ATMS – Instrumentation – Activity 回调基本都是perform打头的方法&＃xff1a;
  Android中Binder用于不同进程之间通信
  

• Instrumentation.java 与之对应的是callActivity打头的方法&＃xff1a;
  

• ActivityThread中调用Instrumentation&＃xff1b;Android P之后对应各种ActivityLifecycleItem

Android P 上新增 Android P Basic lifecycle transaction containers :

1. ActivityThread继承的是ClientTransactionHandler
2. ClientLifecycleManager.java/ClientTransaction.java --> TransactionExecutor.java/ClientTransactionHandler.java
3. ClientTransaction中添加各种流程ActivityLifecycleItem&＃xff0c;执行execute()最终调用的也是 class ActivityThread extends ClientTransactionHandler中方法。将原先class H extends Handler中处理转移到了&＃xff0c;替换EXECUTE_TRANSACTION执行mTransactionExecutor.execute(transaction)。

1.3 Event相关日志

通常比较关注的是wm_on_resume_called&＃xff0c;表示已经准备完成&＃xff0c;界面显示了

frameworks/base/core/java/android/app/EventLogTags.logtags

# See system/core/logcat/event.logtags for a description of the format of this file.
option java_package android.app
# Do not change these names without updating the checkin_events setting in
# google3/googledata/wireless/android/provisioning/gservices.config !!
#
# The activity&＃39;s onPause has been called.
30021 wm_on_paused_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onResume has been called.
30022 wm_on_resume_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onStop has been called.
30049 wm_on_stop_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onCreate has been called.
30057 wm_on_create_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onRestart has been called.
30058 wm_on_restart_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onStart has been called.
30059 wm_on_start_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onDestroy has been called.
30060 wm_on_destroy_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onActivityResult has been called.
30062 wm_on_activity_result_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onTopResumedActivityChanged(true) has been called.
30064 wm_on_top_resumed_gained_called (Token|1|5),(Component Name|3),(Reason|3)
# The activity&＃39;s onTopResumedActivityChanged(false) has been called.
30065 wm_on_top_resumed_lost_called (Token|1|5),(Component Name|3),(Reason|3)


2. 启动应用&＃xff1a;LaunchActivityItem、ResumeActivityItem

如图&＃xff0c;启动应用时添加ClientTransaction中添加了LaunchActivityItem、ResumeActivityItem

1. LaunchActivityItem、ResumeActivityItem都继承BaseClientRequest.java&＃xff0c;基本处理preExecute、execute、postExecute
2. 关注mTransactionExecutor.execute(transaction)处理:

public void execute(ClientTransaction transaction)
// ... ...
executeCallbacks(transaction);
executeLifecycleState(transaction);
// ... ...



1》executeCallbacks(transaction)中transaction.getCallbacks()有LaunchActivityItem执行调用ActivityThread.handleLaunchActivity()&＃xff0c;通过mInstrumentation.callActivityOnCreate()响应Activity.OnCreate()&＃xff0c;执行后状态设置为ActivityClientRecord r.setState(ON_CREATE)
2》executeLifecycleState(transaction)中当前状态start &＃61; ON_CREATE, finish &＃61; ON_RESUME&＃xff0c;中间缺少ON_START&＃xff0c;所以cycleToPath()中间状态mTransactionHandler.handleStartActivity()&＃xff0c;响应Activity.OnStart()&＃xff1b;最后执行请求ResumeActivityItem&＃xff08;即执行ActivityThread.handleResumeActivity()&＃xff09;&＃xff0c;响应Activity.OnResume()

2.1 启动应用流程截图

3 其他流程XXXActivityItem _待续