Android双击两次返回按钮退出程序

private boolean doubleBackToExitPressedOnce = false;

@Override
protected void onResume() {
super.onResume();
// .... other stuff in my onResume ....
this.doubleBackToExitPressedOnce = false;
}

@Override
public void onBackPressed() {
if (doubleBackToExitPressedOnce) {
super.onBackPressed();
return;
}
this.doubleBackToExitPressedOnce = true;
Toast.makeText(this, "在按一次就退出程序了", Toast.LENGTH_SHORT).show();
}