StartActivity的内部代码实现原理

  次阅读 来源:互联网(转载协议) 2016-01-14 10:49 我要评论(0)

1.首先调用Activity的startActivity,-1表示 target Activity finish的时候不通知original Activity

public void startActivity(Intent intent) {

startActivityForResult(intent, -1);

}

2 . 调用Activityd的startActivityForResult方法, Instrumentation class 里面有一个ActivityMonitor 的内部类,用来监控view和system的交互

public void startActivityForResult(Intent intent, int requestCode) {

if (mParent == null) {

Instrumentation.ActivityResult ar =

mInstrumentation.execStartActivity(

this, mMainThread.getApplicationThread(), mToken, this,

intent, requestCode);

if (ar != null) {

mMainThread.sendActivityResult(

mToken, mEmbeddedID, requestCode, ar.getResultCode(),

ar.getResultData());

}

if (requestCode >= 0) {

// If this start is requesting a result, we can avoid making

// the activity visible until the result is received.Setting

// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the

// activity hidden during this time, to avoid flickering.

// This can only be done when a result is requested because

// that guarantees we will get information back when the

// activity is finished, no matter what happens to it.

mStartedActivity = true;

}

} else {

mParent.startActivityFromChild(this, intent, requestCode);

}

}

3. 调用Instrumentation class的 ExecStartActivity:

public ActivityResult execStartActivity(

Context who, IBinder contextThread, IBinder token, Activity target,

Intent intent, int requestCode) {

IApplicationThread whoThread = (IApplicationThread) contextThread;

// 如果找到匹配的Activity,am.mHits++

if (mActivityMonitors != null) {

synchronized (mSync) {

final int N = mActivityMonitors.size();

for (int i=0; i<N; i++) {

final ActivityMonitor am = mActivityMonitors.get(i);

if (am.match(who, null, intent)) {

am.mHits++;

if (am.isBlocking()) {

return requestCode >= 0 ? am.getResult() : null;

}

break;

}

}

}

}

try {

//调用ActivityManagerProxy的startActivity方法

int result = ActivityManagerNative.getDefault()

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