startActivity() from BroadcastReceiver

Question

I am trying to autostart my nightclock application on charging using the following BroadcastReceiver implemented in the onPause() method:

BroadcastReceiver test = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        unregisterReceiver(this);
        Intent i = new Intent(context, NightClock.class);
        i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(i);   
    }           
};
registerReceiver(test, new IntentFilter(Intent.ACTION_POWER_CONNECTED));

The onReceive() method is fired when the USB-cable is plugged in, but the activity doesn't start. However the log shows this:

I/ActivityManager(   79): Starting activity: Intent { flg=0x10000000 cmp=com.meins.nightclock/.NightClock }

Any ideas why the log says the activity is started, but nothing happens?

Answer 1

If your goal is that you want NightClock to be started whenever an ACTION_POWER_CONNECTED broadcast is sent, your approach of using a BroadcastReceiver is fine. However, do not register it from an activity. Rather, register it in the manifest:

<receiver android:name=".OnPowerReceiver">
        <intent-filter>
                <action android:name="android.intent.action.ACTION_POWER_CONNECTED" />
        </intent-filter>
</receiver>

Then, have your BroadcastReceiver as a public Java class (here named OnPowerReceiver, though you can call it whatever you want), and have it call startActivity().

Bear in mind that users probably do not want you doing this. There are many other cases for connecting a phone to power besides starting a "night clock". I humbly suggest you simply let users start your activity via the home screen.

Answer 2

From Docs:

Do not start activities from broadcast receivers because the user experience is jarring; especially if there is more than one receiver. Instead, consider displaying a notification.