Sending your application to background when backbutton is pressed in ANDROID…… OR Detecting whether back Button has been pressed in your ANDROID phone or not.

This code works for all API Levels.

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

The below code works for API level 5 or Higher…..

public class MyActivity extends Activity {
   @Override
  public void onBackPressed() {
    moveTaskToBack(true);
  }
}