is there a default back key(on device) listener in android?

Question

I am having two activities A and B. when i click the button in A that will shows B. when i click the Button in B it backs to A. i had set the overridePendingTransition method after the finish() method. it works properly. but in case the current Activity is B. on that time i click the default back button in the device. it shows the right to left transition to show the Activity A.

How i can listen that Default back key on device?

EDIT:

Log.v(TAG, "back pressed");
finish();
overridePendingTransition(R.anim.slide_top_to_bottom, R.anim.hold);

score 45 · Accepted Answer · answered Apr 07 '10 at 11:58

45

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)  {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
        // do something on back.
        return true;
    }

    return super.onKeyDown(keyCode, event);
}

The following link is a detailed explanation on how to handle back key events, written by the Android developers themselves:

Using the back key

answered Apr 07 '10 at 11:58

Jamie Keeling

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Could you edit your question to show the code your having problems with at the moment? One of us might be able to help – Jamie Keeling Apr 07 '10 at 13:31
just i copy and paste your code snippet in my activity class. just replace the //do somthing on back to my edit code snippet(see the question). – Praveen Apr 07 '10 at 13:37
fine. its working. we have to mention what activity to class. activity.this.finish(); . thats it. Thanks a lot. – Praveen Apr 07 '10 at 14:12
The code for onBackPressed in the link worked perfectly for me. – computercarguy Apr 05 '19 at 18:14
What about from a fragment? – JMB Apr 23 '20 at 05:12

score 29 · Answer 2 · edited Apr 26 '12 at 18:45

29

For Android 2.0 and later, there is a specific method in the Activity class:

@Override  
public void onBackPressed() {
    super.onBackPressed();   
    // Do extra stuff here
}

edited Apr 26 '12 at 18:45

Sam

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answered Apr 07 '10 at 12:19

Nikolay Ivanov

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2

This is the preferred approach for Android 2.x. However, for earlier versions of Android, you still need to use `onKeyDown()`. – CommonsWare Apr 07 '10 at 12:36
not working.... i cant print a statement on logcat itself. i had used both methods. – Praveen Apr 07 '10 at 13:06
I don't know when it changed, but the "super.onBackPressed();" is no longer necessary. – computercarguy Apr 05 '19 at 18:16

score 2 · Answer 3 · answered Apr 07 '10 at 11:50

2

public boolean onKeyDown(int keyCode, KeyEvent event) {
    if(keyCode == KeyEvent.KEYCODE_BACK){
        //Do stuff
    }

    return super.onKeyDown(keyCode, event);
}

answered Apr 07 '10 at 11:50

YaW

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score 0 · Answer 4 · answered Apr 07 '10 at 14:13

0

More info on back key stuff can be found here: http://android-developers.blogspot.com/2009/12/back-and-other-hard-keys-three-stories.html

answered Apr 07 '10 at 14:13

Moss

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score 0 · Answer 5 · answered Jul 18 '10 at 15:57

I use this code on an activity with a media player. I needed to stop the playback when user pressed the back button but still be able to go back to previous activity.

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)  {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
        // do something on back.
        try{
            mp.stop(); //this line stops the player
            return super.onKeyDown(keyCode, event);//this line does the rest 
        }
        catch(IllegalStateException e){
            e.printStackTrace();
        }
        return true;
    }

    return super.onKeyDown(keyCode, event); //handles other keys
}

is there a default back key(on device) listener in android?

5 Answers5

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