Inform Activity from a Broadcastreceiver Only If It Is in The Foreground

Inform Activity from a BroadcastReceiver ONLY if it is in the foreground

So this is almost Bino's answer, but: instead of moving the receiver into the activity, use two receivers, with different Intents. The first one is your original alarm Intent, with a receiver registered in the manifest as you already have, and then that receiver sends a second broadcast intent, which is handled by a receiver registered by the activity as Bino says.

I've done this in my own timer project, on github. Here are the alarm receiver and the requery receiver. Hope that helps.

Can a Broadcast Receiver send information to an Activity only if it is active without starting a new Activity?

There are several different ways to accomplish the same task. One is registering a listener like the following example:

MainActivity

public class MainActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    
        Receiver.setOnReceiveListener(new Receiver.OnReceiveListener() {
            public void onReceive(Context Context, Intent intent)
            {
                //Do something.
            }
        });
    }

    @Override
    protected void onDestroy()
    {
        super.onDestroy();
        Receiver.setOnReceiveListener(null);
    }
}

Receiver

public class Receiver extends BroadcastReceiver
{
    private static OnReceiveListener static_listener;

    public static abstract interface OnReceiveListener
    {
        public void onReceive(Context context, Intent intent);
    }

    public static void setOnReceiveListener(OnReceiveListener listener)
    {
        static_listener = listener;
    }

    @Override
    public final void onReceive(Context context, Intent intent)
    {
        if(static_listener != null) {
            static_listener.onReceive(context, intent);
        }
    }
}

Why BroadcastReceiver works even when app is in background ?

A BroadcastReceiver works when the app is in the background because the event that the receiver picks up are sent globally, and each app is registered to listen in on these, regardless of whether or not it is running.

To deal with this, in your BroadcastReceiver's onReceive code, check if your app is in the foreground.

There is one--and only one that I know of--consistently effective method to do this. You need to keep track of your pause/resume actions for your application. Ensure that you check this in every activity.

There is some sample code in this answer (solution #1). In your case, you would want to check MyApplication.isActivityVisible() == true as a validation before doing anything from your BroadcastReceiver.

Broadcast receiver is not working when app on foreground or active

As I understood,
when you start application in first time, you see nothing, just service is started and a broadcast receiver is registered. When battery level will be changed, the method checkBatteryLevel() is calling and the broadcast receiver will be unregistered. As result you have never received a new changing of battery level.

How to know in BroadcastReceiver if App is running on foreground?

Try this way hope this works for you

public class MyBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        if (isAppForground(context)) {
            // App is in Foreground
        } else {
            // App is in Background
        }
    }

    public boolean isAppForground(Context mContext) {

        ActivityManager am = (ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE);
        List<RunningTaskInfo> tasks = am.getRunningTasks(1);
        if (!tasks.isEmpty()) {
            ComponentName topActivity = tasks.get(0).topActivity;
            if (!topActivity.getPackageName().equals(mContext.getPackageName())) {
                return false;
            }
        }

        return true;
    }

}

Add this permission

<uses-permission android:name="android.permission.GET_TASKS" />

---

Related Topics