Q:

Moving application in background on back button event

Is it possible to move the app in background when we click on device back button in android?
background means application moves to screen(application) from where it launches ?

A:

Try Using 
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) 
{
    switch(keyCode)
    {
        case KeyEvent.KEYCODE_BACK:

            moveTaskToBack(true);

            return true;
    }
    return false;
}

A:

@Override
public void onBackPressed() {
    moveTaskToBack(true);
}

A:

I will prefer to use below code to move application in background
       @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) 
    {
        switch(keyCode)
        {
            case KeyEvent.KEYCODE_BACK:
              if(isTaskRoot()) {
               Intent homeIntent = new Intent(Intent.ACTION_MAIN);
               homeIntent.addCategory(Intent.CATEGORY_HOME);
               homeIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
               startActivity(homeIntent);
               return true;
                }
            else {
             super.keyDown(keyCode,event);
             return false;      
        }

    default: 
    super.keyDown(keyCode,event);
           return false;
 }

}

