Registering and unregistering BroadcastReceiver in a fragment

My app has an action bar with 3 fragment tabs. In the second fragment I register and unregister a BroadcastReceiver. I unregister the receiver in onPause and register it in onCreateView and in onResume.

getActivity().registerReceiver(this.batteryInfoReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));

and

getActivity().unregisterReceiver(batteryInfoReceiver);

1) Is it all right to register the same reciever twice (in onCreateView and onResume)?(is it harmless?)

2) Is it enough to just register the reciever in onResume?

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最佳答案

Have a look at life-cycle of Fragments:

onCreateView(): The system calls this when it's time for the fragment to draw its user interface for the first time. To draw a UI for your fragment, you must return a View from this method that is the root of your fragment's layout. You can return null if the fragment does not provide a UI.

onResume(): The fragment is visible in the running activity

onPause(): This is usually where you should commit any changes that should be persisted beyond the current user session (because the user might not come back).

Conclusion:

So it is better to register the receiver only inside ABC0 and unregister inside onPause() because onCreateView() deals with view hierarchy only. It has nothing to do with receiver. So it is not harmful but surely it is useless.

I hope it will be helpful!!

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Here is code that works for me:

Inside layout:

<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="sendInternalBroadcast"
android:text="Broadcast"/>

Fragment Layout:

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:gravity="center">


<TextView
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="Fragment One"
android:id="@+id/fragmentoneTextView1"/>


</LinearLayout>

inside Main Activity:

    public void sendInternalBroadcast(View view)
{
Intent intent = new Intent();
intent.setAction("com.codingbadly.stefanronnkvist.simplebroadcastreceiver.setup");
intent.putExtra("From", "sendInternalBroadcast");
sendBroadcast(intent);
}

Fragment:

import android.app.*;
import android.content.*;
import android.os.*;
import android.view.*;
import android.widget.*;


public class FragmentOne extends Fragment
{
View view;
Context _context;
PendingIntent pi;
BroadcastReceiver br;
AlarmManager am;


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
view = inflater.inflate(R.layout.fragmentone, container, false);
setup();
return view;
}


@Override
public void onAttach(Context context)
{
super.onAttach(context);
_context = context;
}


@Override
public void onDestroyView()
{
super.onDestroyView();
_context.unregisterReceiver(br);
}




private void setup()
{
br = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent i)
{
TextView tv = (TextView)view.findViewById(R.id.fragmentoneTextView1);
tv.setText("onReceive");
}
};
_context.registerReceiver(br, new IntentFilter("com.codingbadly.stefanronnkvist.simplebroadcastreceiver.setup"));
pi = PendingIntent.getBroadcast(_context, 0, new Intent("com.codingbadly.stefanronnkvist.simplebroadcastreceiver.setup"), 0);
am = (AlarmManager)(_context.getSystemService(Context.ALARM_SERVICE));
}
}

Good Luck.. Stefan Ronnkvist

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OnResume Register: 

context.registerReceiver(receiver,IntentFilter(BroadCastAction.action_success))

onPause unRegister :

context.unregisterReceiver(mContactBroadCastReceiver);
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With Fragment, you will end up getting the exception Receiver not registered in some cases as in my case.

To resolve this, I used

 LocalBroadcastManager.getInstance(ctx).registerReceiver(myReceiver,IntentFilter(...))

instead of

 activity.registerReceiver(paxAmountReceiver,IntentFilter(...))

Similarly to unregister, use in onDestroyView() (For Eg.)

LocalBroadcastManager.getInstance(ctx).unregister(myReceiver)

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