问题
Basically, this is what I'm doing
1) Set AlarmManager to execute BroadcastReceiver (BCR)
Intent intent = new Intent(m_Context, BCR.class);
intent.putExtras(extras);
PendingIntent pendingIntent = PendingIntent.getBroadcast(m_Context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
AlarmManager am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
am.set(AlarmManager.RTC_WAKEUP, StartTime, pendingIntent)
2) Start MyActivity from BCR
@Override
public void onReceive(Context context, Intent intent) {
Intent newIntent = new Intent(context, MyActivity.class);
newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
context.startActivity(newIntent);
}
3) Have MyActivity turn on the screen if its not on
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().addFlags(LayoutParams.FLAG_DISMISS_KEYGUARD);
getWindow().addFlags(LayoutParams.FLAG_SHOW_WHEN_LOCKED);
getWindow().addFlags(LayoutParams.FLAG_TURN_SCREEN_ON);
setContentView(R.layout.myactivity);
}
@Overide
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
}
For some reason, I notice that right when MyActivity is opened, it's flow goes like:
onCreate/onNewIntent -> onResume -> onPause -> onResume
I'm not sure why it does an onPause right away. I notice this only happens when the screened is being turned on by the flags. Does anyone know why this happens? Is there any way this behavior can be prevented?
回答1:
Just in case anyone else runs into this, I seem to notice this behaviour only when I inflate fragments inside of an activity via XML layout. I don't know if this behaviour also happens with the compatibility library version of Fragments (I'm using android.app.Fragment)
It seems the activity will call Activity#onResume once before calling Fragment#onResume to any added Fragments, and then will call Activity#onResume again.
- Activity:onCreate
- Fragment:onAttach
- Activity:onAttachFragments
- Fragment:onCreate
- Activity: onStart
- Activity: onResume
- Fragment: onResume
- Activity: onResume
回答2:
If you have ES File Explorer then FORCE STOP it. Somehow, they interrupt your app's lifecycle (comments suggest some kind of overlay).
My issue with onResume being caused twice was because onPause was somehow being called after the activity was created.. something was interrupting my app.
And this only happens after being opened for the first time after installation or built from studio.
I got the clue from another post and found out it was because of ES File Explorer. Why does onResume() seem to be called twice?
As soon as I force stop ES File Explorer, this hiccup behavior no longer happens... it's frustrating to know after trying many other proposed solutions. So beware of any other interrupting apps like this one.
回答3:
if you trying request permissions every time it can cause such problems, just check if you already granted them
requestPermissions can cause it:
onCreate
onStart
onResume
onPause
onResume
回答4:
I was researching about this for a while because on the internet there is no any mention about this weird behaviour. I don't have a solution how to overcome this dark-side-behavior but I have found an exact scenario when it certainly happens.
onPause-onResume-onPause-onResume just happens every time, when app is starting first time after installation. You can simply invoke this behavior by doing any change in code and rerunning (which includes recompiling) the app from your IDE.
No matter if you use AppCompat libs or not. I have tested both cases and behavior carries on.
Note: Tested on Android Marshmallow.
I have borrowed the code from this thread about fragment and activity lifecycle and here it is (just copy, paste, declare activity in manifest and run Forest run):
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentTransaction;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class TestActivity extends Activity {
private static final String TAG = "ACTIVITY";
public TestActivity() {
super();
Log.d(TAG, this + ": this()");
}
protected void finalize() throws Throwable {
super.finalize();
Log.d(TAG, this + ": finalize()");
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, this + ": onCreate()");
TextView tv = new TextView(this);
tv.setText("Hello world");
setContentView(tv);
if (getFragmentManager().findFragmentByTag("test_fragment") == null) {
Log.d(TAG, this + ": Existing fragment not found.");
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.add(new TestFragment(), "test_fragment").commit();
} else {
Log.d(TAG, this + ": Existing fragment found.");
}
}
@Override
public void onStart() {
super.onStart();
Log.d(TAG, this + ": onStart()");
}
@Override
public void onResume() {
super.onResume();
Log.d(TAG, this + ": onResume()");
}
@Override
public void onPause() {
super.onPause();
Log.d(TAG, this + ": onPause()");
}
@Override
public void onStop() {
super.onStop();
Log.d(TAG, this + ": onStop()");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG, this + ": onDestroy()");
}
public static class TestFragment extends Fragment {
private static final String TAG = "FRAGMENT";
public TestFragment() {
super();
Log.d(TAG, this + ": this() " + this);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, this + ": onCreate()");
}
@Override
public void onAttach(final Context context) {
super.onAttach(context);
Log.d(TAG, this + ": onAttach(" + context + ")");
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d(TAG, this + ": onActivityCreated()");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.d(TAG, this + ": onCreateView()");
return null;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Log.d(TAG, this + ": onViewCreated()");
}
@Override
public void onDestroyView() {
super.onDestroyView();
Log.d(TAG, this + ": onDestroyView()");
}
@Override
public void onDetach() {
super.onDetach();
Log.d(TAG, this + ": onDetach()");
}
@Override
public void onStart() {
super.onStart();
Log.d(TAG, this + ": onStart()");
}
@Override
public void onResume() {
super.onResume();
Log.d(TAG, this + ": onResume()");
}
@Override
public void onPause() {
super.onPause();
Log.d(TAG, this + ": onPause()");
}
@Override
public void onStop() {
super.onStop();
Log.d(TAG, this + ": onStop()");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG, this + ": onDestroy()");
}
}
}
回答5:
I don't know for sure what's going on, but I suspect that your activity is being restarted because setting the screen on is treated by the system as a configuration change. You might try logging the configuration on each call to onResume to see if that's what's happening and, if so, what is actually changing. You can then modify the manifest to tell the system that your activity will handle the change on its own.
protected void onResume() [
super.onResume();
Configuration config = new Configuration();
config.setToDefaults();
Log.d("Config", config.toString());
. . .
}
回答6:
I have similar problem. My situation was next CurrentActivity extends MainActivity CurrentFragment extends MainFragment
I was opening CurrentActivity with intent as usually. In onCreate CurrentAcitivity I was replacing CurrentFragment.
Life Cycle was: 1. onResume MainActivity 2. onResume CurrentActivity 3. onResume MainFragment 4. onResume CurrentFragment
called onPause Automatically, and after that again
- onResume MainActivity
- onResume CurrentActivity
- onResume MainFragment
- onResume CurrentFragment
I decide to retest everything and after few hours spend trying and playing I found root issue. In MainFragment onStart I was calling startActivityForResult every time (in my case android popup for turning on Wifi) which was call onPause on MainFragment. And all of us know that after onPause next is onResume.
So its not Android bug, it's only mine :-)
Happy lifecycle debuging!
回答7:
I had a similar issue, and my problem was that at the onCreate() method, I was doing:
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
super.setContentView(R.layout.friends); <-- problem
}
My call to "super." was triggering the onResume() twice. It worked as intended after I changed it to just:
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.friends); <-- 'super.' removed
}
Hope it helps.
回答8:
I also ran into this onresume-onpause-onresume sequence (on 4.1.2 and above, but I did not experience this on 2.3). My problem was related to wakelock handling: I accidentally forgot to release a wakelock and reacquiring it caused an error with a message "WakeLock finalized while still held". This problem resulted in onPause being called immediately after onResume and resulted in faulty behavior.
My suggestion is: check for errors in the log, those might be related to this issue.
Another hint: turning on the screen might be a bit more tricky than simply using window flags. You might want to check this answer here - it suggests you set up a receiver to check if the screen has already been turned on and launch the desired activity only after: https://stackoverflow.com/a/16346369/875442
回答9:
It seems that using Activity from the support library saves and restores instance automatically. Therefore, only do your work if savedInstanceState is null.
回答10:
I just ran into this, and it seems that getWindow().addFlags() and tweaking Window properties in general might be a culprit.
When my code is like this
@Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_generic_fragment_host);
// performing fragment transaction when instance state is null...
onResume() is triggered twice, but when I remove requestWindowFeature(), it's only called once.
回答11:
I think you should have a look at that question: Nexus 5 going to sleep mode makes activity life cycle buggy You should find leads
回答12:
Basically a lot of stuff can trigger this. Some resume processes that loses focus can do it. A few apps will cause it to happen too. The only way to cope is to block the double running. Note, this will also have an errant pause thrown in for good measure.
boolean resumeblock = false;
@Override
protected void onResume() {
super.onResume();
sceneView.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
sceneView.getViewTreeObserver().removeOnPreDrawListener(this);
if (resumeblock) return false;
resumeblock = true;
//Some code.
return false;
}
});
}
This is a solid way to prevent such things. It will block double resumes. But, it will also block two resumes that preserve the memory. So if you just lost focus and it doesn't need to rebuild your stuff. It will block that too. Which might be a benefit clearly, since if you're using the resume to control some changes over focus, you only actually care if you need to rebuild that stuff because of focus. Since the pre-draw listeners can only be called by the one thread and they must be called in sequence, the code here will only run once. Until something properly destroys the entire activity and sets resumeblock back to false.
回答13:
i also faced this issue this is because of fragments..
the number of fragments you have in activity onResume() will call that number of times. to overcome i used flag variables in SharedPrefrences
回答14:
as @TWL said
ES File Explorer
was the issue for me !
Uninstalling the app solved the problem.
When this ES File Explorer was installed, onStart() -> onResume() -> onPause() -> onResume() .. was the problem.
onResume() was called 2'ce.
回答15:
I had the same problem. Mine was for this code in runtime
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
I just put it in manifest
android:screenOrientation="landscape"
no more problem about twice call to onCreate and onResume.
来源：https://stackoverflow.com/questions/16026756/why-is-my-onresume-being-called-twice