Detect home button press in android

Question

This has been driving me nuts for a while now.

Is there any way of reliably detecting if the home button has been pressed in an android application?

Failing that, is there a robust way of telling what caused an activity to go into onPause? i.e Can we detect if it was caused by a new activity launching or by pressing back/home.

One suggestion I have seen is to override onPause() and call isFinishing() but this will return false when pressing the home button just as it would if a new activity is starting so this fails to distinguish between the two.

Any help much appreciated.

** Update** : Thanks to @android-hungry for this link: https://nishandroid.blogspot.com/

Overiding the following method:

@Override
public void onAttachedToWindow() {
    super.onAttachedToWindow();
    this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);           
}

Then the following event WILL get fired for home button presses:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {     

    if(keyCode == KeyEvent.KEYCODE_HOME)
    {
       //The Code Want to Perform. 
    }
});

I'm not sure if there are any side effects with this line:

this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);   

So it would seem that contrary to popular belief, you can in fact listen out for the home key. Worryingly, you can return false and have the home key do nothing.

Update: As expected, there are some side affects with this - it seems that embedded videos and google maps are not visible with this mode enabled.

Update: Supposedly this hack no longer works as of Android 4.0 onwards

Answer 1

Following code works for me :)

HomeWatcher mHomeWatcher = new HomeWatcher(this); mHomeWatcher.setOnHomePressedListener(new OnHomePressedListener() {     @Override     public void onHomePressed() {         // do something here...     }     @Override     public void onHomeLongPressed() {     } }); mHomeWatcher.startWatch(); 

import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.util.Log;  public class HomeWatcher {      static final String TAG = "hg";     private Context mContext;     private IntentFilter mFilter;     private OnHomePressedListener mListener;     private InnerReceiver mReceiver;      public HomeWatcher(Context context) {         mContext = context;         mFilter = new IntentFilter(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);     }      public void setOnHomePressedListener(OnHomePressedListener listener) {         mListener = listener;         mReceiver = new InnerReceiver();     }      public void startWatch() {         if (mReceiver != null) {             mContext.registerReceiver(mReceiver, mFilter);         }     }      public void stopWatch() {         if (mReceiver != null) {             mContext.unregisterReceiver(mReceiver);         }     }      class InnerReceiver extends BroadcastReceiver {         final String SYSTEM_DIALOG_REASON_KEY = "reason";         final String SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS = "globalactions";         final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";         final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";          @Override         public void onReceive(Context context, Intent intent) {             String action = intent.getAction();             if (action.equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {                 String reason = intent.getStringExtra(SYSTEM_DIALOG_REASON_KEY);                 if (reason != null) {                     Log.e(TAG, "action:" + action + ",reason:" + reason);                     if (mListener != null) {                         if (reason.equals(SYSTEM_DIALOG_REASON_HOME_KEY)) {                             mListener.onHomePressed();                         } else if (reason.equals(SYSTEM_DIALOG_REASON_RECENT_APPS)) {                             mListener.onHomeLongPressed();                         }                     }                 }             }         }     } } 

public interface OnHomePressedListener {     void onHomePressed();     void onHomeLongPressed(); } 

Answer 2

This is an old question but it might help someone.

@Override protected void onUserLeaveHint() {     Log.d("onUserLeaveHint","Home button pressed");     super.onUserLeaveHint(); } 

According to the documentation, the onUserLeaveHint() method is called when the user clicks the home button OR when something interrupts your application (like an incoming phone call).

This works for me.. :)

Answer 3

It is impossible to detect and/or intercept the HOME button from within an Android app. This is built into the system to prevent malicious apps that cannot be exited.

Answer 4

I needed to start/stop background music in my application when first activity opens and closes or when any activity is paused by home button and then resumed from task manager. Pure playback stopping/resuming in Activity.onPause() and Activity.onResume() interrupted the music for a while, so I had to write the following code:

@Override
public void onResume() {
  super.onResume();

  // start playback here (if not playing already)
}

@Override
public void onPause() {
  super.onPause();

  ActivityManager manager = (ActivityManager) this.getSystemService(Activity.ACTIVITY_SERVICE);
  List<ActivityManager.RunningTaskInfo> tasks = manager.getRunningTasks(Integer.MAX_VALUE);
  boolean is_finishing = this.isFinishing();
  boolean is_last = false;
  boolean is_topmost = false;
  for (ActivityManager.RunningTaskInfo task : tasks) {
    if (task.topActivity.getPackageName().startsWith("cz.matelier.skolasmyku")) {
      is_last = task.numRunning == 1;
      is_topmost = task.topActivity.equals(this.getComponentName());
      break;
    }
  }

  if ((is_finishing && is_last) || (!is_finishing && is_topmost && !mIsStarting)) {
    mIsStarting = false;
    // stop playback here
  }
}

which interrupts the playback only when application (all its activities) is closed or when home button is pressed. Unfortunatelly I didn't manage to change order of calls of onPause() method of the starting activity and onResume() of the started actvity when Activity.startActivity() is called (or detect in onPause() that activity is launching another activity other way) so this case have to be handled specially:

private boolean mIsStarting;

@Override
public void startActivity(Intent intent) {
  mIsStarting = true;
  super.startActivity(intent);
}

Another drawback is that this requires GET_TASKS permission added to AndroidManifest.xml:

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

Modifying this code that it only reacts on home button press is straighforward.