Application、Activity的启动流程(9.0)

1、通过ActivityThread的静态main()方法创建new ActivityThread()实例，及其成员变量mAppThread = new ApplicationThread()

android.app.ActivityThread#main
Looper.prepareMainLooper();
ActivityThread thread = new ActivityThread();
thread.attach(false, startSeq);
Looper.loop();

2、App进程的ActivityThread#attach通过Binder IPC向system_server进程ActivityManagerService服务发送attachApplication请求

android.app.ActivityThread#attach
final IActivityManager mgr = ActivityManager.getService();
mgr.attachApplication(mAppThread, startSeq);

3、system_server进程通过Binder IPC向App进程发送bindApplication。

ApplicationThread收到bindApplication后通过handler发送H.BIND_APPLICATION进而调用ActivityThread#handleBindApplication，创建new Instrumentation()实例
进而newApplication，调用Application的attach方法、onCreate方法

com.android.server.am.ActivityManagerService#attachApplicationLocked
android.app.ActivityThread.ApplicationThread#bindApplication
android.app.ActivityThread#handleBindApplication
mInstrumentation = new Instrumentation();
app = data.info.makeApplication(data.restrictedBackupMode, null);
mInstrumentation.callApplicationOnCreate(app);

3.1、newApplication的过程

android.app.LoadedApk#makeApplication
ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
app = mActivityThread.mInstrumentation.newApplication(
cl, appClass, appContext);

android.app.Instrumentation#newApplication(java.lang.ClassLoader, java.lang.String, android.content.Context)
Application app = getFactory(context.getPackageName()).instantiateApplication(cl, className);
app.attach(context);

4、Activity的attach()方法执行流程

android.app.ActivityThread#handleRelaunchActivity
android.app.ActivityThread#handleRelaunchActivityInner
android.app.ActivityThread#handleLaunchActivity
android.app.ActivityThread#performLaunchActivity
activity = mInstrumentation.newActivity(cl, component.getClassName(), r.intent);
activity.attach(...)

android.app.Activity#attach
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mUiThread = Thread.currentThread();
mMainThread = mActivityThread
mInstrumentation = instr;

补充：
ApplicationThread的作用是：
实现双向Binder IPC
private class ApplicationThread extends IApplicationThread.Stub
App进程向system_server进程的Binder IPC，通过ActivityManager.getService()得到IActivityManager
system_server进程向App进程的Binder IPC，通过ApplicationThread

Launcher启动Activity的流程.png

参考：
一个APP从启动到主页面显示经历了哪些过程？
App启动流程涉及到的类介绍
Android 组件系列 -- Activity 启动流程(9.0)