Activity.startActivity(Intent intent)----Activity.startActivityForResult(Intent intent)----Instrumentation.execStartActivity()----ActivityManagerNative.getDefault().startActivity----ActivityManagerService----Binder----IActivityManager----ActivityManagerProxy----ActivityManagerService.startActivity----ActivityManagerService.startActivityAsUser设置了userId-----ActivityStackSuperviso.startActivityMayWait主要进行了Intent的检查----ActivityStackSuperviso.startActivityLocked生成ActivityRecord-----ActivityStackSuperviso.startActivityUncheckedLocked首先判断了启动模式------上面的步骤完成了Activity的目标栈的判断(targetStack)------ActivityStack.startActivityLocked将Activity添加到了栈顶，初始化了WindowManager--------StackSupervisor.resumeTopActivitiesLocked判断目标任务栈是否在前------ActivityStack.resumeTopActivityLocked确保当前栈顶的Activity是否resumed-------ActivityStack.resumeTopActivityInnerLocked 1，首先让现在正在运行的Activity调用startPausingLocked进入pause状态 2.如果要启动的Activity不为空且所在的进程存在的话，所在的进程执行scheduleResumeActivity启动Activity 3.如果Activity为空，所在的进程不存在，执行ActivityStackSupervisor.startSpecificActivityLocked
callCallActivityOnSaveInstanceState(r)----Instrumentation.callActivityOnPause---Activity.performPause---Activity.onPause() Instrumentation.callActivityOnReusme---Activity.performReusme---Activity.onReusme()
Looper.prepareMainLooper()Looper.loop();----ActivityThread thread = new ActivityThread(); thread.attach(false)---------ActivityManagerService.attachApplication----------ActivityManagerService.attachApplicationLocked-------ActivityStackSupervisor.realStartActivityLocked-------ApplicationThread.scheduleLaunchActivity-----ActivityThread.handleLaunchActivity----ActivityThread.performLaunchActivity----packageInfo.getClassLoader() mInstrumentation.newActivity----- activity.attach(---- mInstrumentation.callActivityOnCreate activity.performStart(); mInstrumentation.callActivityOnRestoreInstanceState( prePerformCreate(activity); activity.performCreate(icicle, persistentState); postPerformCreate(activity);---activity.performCreate()----activity.Create()原文：https://www.cnblogs.com/ldq2016/p/10243592.html