Question

Problem:

I am trying to write an app that executes some code when the phone is plugged into a power source which is determined to be a PC, as opposed to an AC port. I also want this app to have a gui interface which the user can “force” start that same code.

I have 2 classes so far: one is the main activity and the other one is a class that extends BroadcastReceiver.

Code is below:

MainActivity.java

public class MainActivity extends Activity{

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    public void func1(View view){ //stuff        }

    public void func2(View view){ //stuff        }
}

ChargingOnReceiver.java

public class ChargingOnReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
    // TODO Auto-generated method stub
        CharSequence text = "Plug status = " + isUSBConnected(context);
        int duration = Toast.LENGTH_SHORT;
        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }
    public static boolean isUSBConnected(Context context){
        Intent intent = context.registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
        int plugged = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
        return plugged == BatteryManager.BATTERY_PLUGGED_USB;
    }
}

AndroidManifest.xml

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

Side Question:

So a quick first question: How can I call methods in MainActivity from ChargingOnReceiver (e.g. func1 or fucn2)? For example, my isUSBConnected() function used to be in MainActivity but I couldn’t find a way to call it from ChargingOnReceiver so I moved it to ChargingOnReceiver.

Main Question:

The code errors out with:
*FATAL EXCEPTION: main:: java.lang.RuntimeException: Unable to start receiver com.example.ChargingOnReceiver: android.content.ReceiverCallNotAllowedException: IntentReceiver components are not allowed to register to receive intents
*

I kind of understand why it is erroring out, as I’m trying to register a receiver within a receiver, but could someone point me in the direction of how I would be able to do this correctly?

Answer 1

Instead of:

context.registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));

use:

context.getApplicationContext().registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));

This is annoying — registerReceiver() should be smarter than this — but it’s the workaround for this particular case.