Registering and unregistering BroadcastReceiver in a fragment

Question

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?

Answer 1

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 onResume() 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!!

Answer 2

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