How to handle back button in activity

Question

How to handle a back button in an activity. Where I have some buttons. If I click one of the button it's redirecting to the buttons which I required. It's working fine but When I press back button it gets finished.

How to solve this problem. I have only one activity for all those buttons. Thanks in advance.

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) 
   {
        if ((keyCode == KeyEvent.KEYCODE_BACK)) 
        {
            return false; //I have tried here true also
        }
        return super.onKeyDown(keyCode, event);
   }

I have used above code to handle back button but its not working. When I press back button its struck there itself.

Answer 1

You should use:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)  {
    if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.ECLAIR
            && keyCode == KeyEvent.KEYCODE_BACK
            && event.getRepeatCount() == 0) {
        // Take care of calling this method on earlier versions of
        // the platform where it doesn't exist.
        onBackPressed();
    }

    return super.onKeyDown(keyCode, event);
}

@Override
public void onBackPressed() {
    // This will be called either automatically for you on 2.0
    // or later, or by the code above on earlier versions of the
    // platform.
    return;
}

As defined here: http://android-developers.blogspot.com/2009/12/back-and-other-hard-keys-three-stories.html

If you are using an older version to compile the code, replace android.os.Build.VERSION_CODES.ECLAIR by 5 (you can add a private int named ECLAIR for example)

Answer 2

This helped me ..

@Override
public void onBackPressed() {
    startActivity(new Intent(currentActivity.this, LastActivity.class));
    finish();
}

OR????? even you can use this for drawer toggle also

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
        startActivity(new Intent(currentActivity.this, LastActivity.class));
    finish();

}

I hope this would help you.. :)

Answer 3

You can handle it like this:

for API level 5 and greater

@Override
public void onBackPressed() {
    // your code.
}

older than API 5

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        // your code
        return true;
    }

    return super.onKeyDown(keyCode, event);
}

Answer 4

In addition to the above I personally recommend

onKeyUp():

Programatically Speaking keydown will fire when the user depresses a key initially but It will repeat while the user keeps the key depressed.*

This remains true for all development platforms.

Google development suggested that if you are intercepting the BACK button in a view you should track the KeyEvent with starttracking on keydown then invoke with keyup.

public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK
            && event.getRepeatCount() == 0) {
        event.startTracking();
        return true;
    }
    return super.onKeyDown(keyCode, event);
}

public boolean onKeyUp(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.isTracking()
            && !event.isCanceled()) {
        // *** Your Code ***
        return true;
    }
    return super.onKeyUp(keyCode, event);
}

Answer 5

For both hardware device back button and soft home (back) button e.g. " <- " this is what works for me. (*Note I have an app bar / toolbar in the activity)

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            //finish();
            onBackPressed();
            break;
    }
    return true;
}



@Override
public void onBackPressed() {
   //Execute your code here
   finish();

}

Cheers!

Answer 6

A simpler approach is to capture the Back button press and call moveTaskToBack(true) as follows:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        moveTaskToBack(true);
        return true;
    }
    return super.onKeyDown(keyCode, event);
}

Android 2.0 introduced a new onBackPressed method, and these recommendations on how to handle the Back button