Asked  7 Months ago    Answers:  5   Viewed   112 times

I currently have an Activity that when it gets displayed a Notification will also get displayed in the Notification bar.

This is so that when the User presses home and the Activity gets pushed to the background they can get back to the Activity via the Notification.

The problem arises when a User presses the back button, my Activity gets destroyed but the Notification remains as I want the user to be able to press back but still be able to get to the Activity via the Notification. But when a USER tries this I get Null Pointers as its trying to start a new activity rather than bringing back the old one.

So essentially I want the Back button to act the exact same as the Home button and here is how I have tried so far:


        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event)  {
            if (Integer.parseInt(android.os.Build.VERSION.SDK) < 5
                    && keyCode == KeyEvent.KEYCODE_BACK
                    && event.getRepeatCount() == 0) {
                Log.d("CDA", "onKeyDown Called");
                onBackPressed();
            }

            return super.onKeyDown(keyCode, event);
        }

        public void onBackPressed() {
            Log.d("CDA", "onBackPressed Called");
            Intent setIntent = new Intent(Intent.ACTION_MAIN);
            setIntent.addCategory(Intent.CATEGORY_HOME);
            setIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            startActivity(setIntent); 

            return;
        }   

However the above code still seems to allow my Activity to be destroyed, How can I stop my Activity from being destroyed when the back button is pressed?

 Answers

39

Remove your key listener or return true when you have KEY_BACK.

You just need the following to catch the back key (Make sure not to call super in onBackPressed()).

Also, if you plan on having a service run in the background, make sure to look at startForeground() and make sure to have an ongoing notification or else Android will kill your service if it needs to free memory.

@Override
public void onBackPressed() {
   Log.d("CDA", "onBackPressed Called");
   Intent setIntent = new Intent(Intent.ACTION_MAIN);
   setIntent.addCategory(Intent.CATEGORY_HOME);
   setIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
   startActivity(setIntent);
}
Tuesday, June 1, 2021
 
PLPeeters
answered 7 Months ago
63

Use getActionBar().setDisplayHomeAsUpEnabled(false) to remove the home button from the action bar.

Monday, August 9, 2021
 
TomPuts
answered 4 Months ago
34

But if the button is held down longer, Android opens up the soft keyboard on the bottom half of the screen.

What phone do you have? Are you sure? I've never once seen that happen and I just tried it and it doesn't work on my phone.

Also, that sounds like a user problem. Don't try to subvert the user. If the user REALLY wants to open a keyboard in your app, you should let them and if it's useless, they'll hit back and it will go away.

A more concerning issue should be that your buttons are so close to the menu buttons.

Thursday, August 12, 2021
 
swydell
answered 4 Months ago
79
pd.setCancelable(true);
    pd.setOnCancelListener(cancelListener);
    bCancelled=false;

 pd is your progressdialog box

and now use cancelListner

    OnCancelListener cancelListener=new OnCancelListener(){
    @Override
    public void onCancel(DialogInterface arg0){
        bCancelled=true;
        finish();
    }
};
Wednesday, September 22, 2021
 
user1024047
answered 3 Months ago
20

This question is already answered, but I feel to clear something here in this topic. Most comments and answeres point out to use super.onBackPressed() and that this is the cause of the not working method onBackPressed(). But that is not correct and important to let other beginners know. The method onBackPressed() does not need to use super.onBackPressed() . onBackPressed()also works if somebody, for example, comment super.onBackPressed() out.

As the questionier has written, he won´t use super.onBackPressed() because it will close the activity. So, the cause of this why it isn´t working, could be seperated into three possible causes:

  1. The Log doesn´t work because of a wrong filter in the logcat console
  2. The Toast dosn´t work because of the wrong passed context
  3. The OS is implemented wrong by the supplier.

Usually, the toast works by passing the correct context. In the case of questioner, simply passing this .

@Override
public void onBackPressed() {
    Log.d("MainActivity","onBackPressed");
    Toast.makeText(this,"onBackPressed",Toast.LENGTH_SHORT).show();
}

For the Log, simply set the correct filter on logcat.

I don´t care if somebody give downvotes now, but it must be clear for other beginners, that super.onBackPressed() must not be used.

Anyway, the use of onKeyDown() also is a solution.

Thursday, October 7, 2021
 
Sean
answered 2 Months ago
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