Show toast of the most recently opened application in android

Question

I am trying to create a service that will show a toast every second with the most recent running application. Every time I start the service, I get a NullPointerException. What can I do to avoid this?

public class CheckRunningActivity extends Service {
private static final String TAG = "CheckRunningActivity";
boolean checkApps;
private Timer mTimer = null;
private Handler mHandler = new Handler();
private ActivityManager am;

public static final long NOTIFY_INTERVAL = 1000; // 1 second

    @Override
    public void onDestroy() {
        mTimer.cancel();
    }
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }

@Override
public void onCreate() {
    Log.d(TAG, "I created it");   

     ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);

     // cancel if already existed
    if(mTimer != null) {
        mTimer.cancel();
    } else {
        // recreate new
        mTimer = new Timer();
    }
    // schedule task
    mTimer.scheduleAtFixedRate(new TimeDisplayTimerTask(), 0, NOTIFY_INTERVAL);
}



class TimeDisplayTimerTask extends TimerTask {

    @Override
    public void run() {

        // run on another thread
        mHandler.post(new Runnable() {

            @Override
            public void run() {
                Log.d(TAG, "Its running");   

        String packageName = am.getRunningTasks(1).get(0).topActivity
                .getPackageName();

            Toast.makeText(getBaseContext(), packageName, Toast.LENGTH_LONG).show();
            Log.d(TAG, "Make Toast");           
            }
        });
     }
 }

}

try cehcking for null before doing `mTimer.cancel();` in `onDestroy()`. — faizal, Jul 03 '14 at 08:09
your original comment was correct. It was a silly mistake. I just overlooked my AM initialization. Thank you for suggesting that I recheck it. — Trent Pierce, Jul 03 '14 at 08:10
your welcome. i deleted my original comment after seeing the initialization in the edited question :) — faizal, Jul 03 '14 at 08:11

score 0 · Answer 1 · edited May 23 '17 at 11:57

0

you can't directly call toast from service . you need a handler for this. see answer here.

edited May 23 '17 at 11:57

Community

1
1

answered Jul 03 '14 at 08:04

Waqar Ahmed

5,005
2
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score 0 · Accepted Answer · answered Jul 03 '14 at 08:09

after looking at the code again, I realized that I had not properly initialized the Activity Manager.

Here is the corrected code...

public class CheckRunningActivity extends Service {
private static final String TAG = "CheckRunningActivity";
boolean checkApps;
private Timer mTimer = null;
private Handler mHandler = new Handler();
private ActivityManager am;

public static final long NOTIFY_INTERVAL = 1000; // 1 second

    @Override
    public void onDestroy() {
        mTimer.cancel();
    }
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }

@Override
public void onCreate() {
    Log.d(TAG, "I created it");   


     // cancel if already existed
    if(mTimer != null) {
        mTimer.cancel();
    } else {
        // recreate new
        mTimer = new Timer();
    }
    // schedule task
    mTimer.scheduleAtFixedRate(new TimeDisplayTimerTask(), 0, NOTIFY_INTERVAL);
}



class TimeDisplayTimerTask extends TimerTask {

    @Override
    public void run() {

        // run on another thread
        mHandler.post(new Runnable() {

            @Override
            public void run() {
                ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
                Log.d(TAG, "Its running");   

        String packageName = am.getRunningTasks(1).get(0).topActivity.getPackageName();

            Toast.makeText(getBaseContext(), packageName, Toast.LENGTH_LONG).show();
            Log.d(TAG, "Make Toast");           
            }
        });
     }
 }          
}

Show toast of the most recently opened application in android

2 Answers2