如何解决按返回键时退出整个应用程序

既然选择了作为一名程序猿，那么就无谓任何BUG_________FantasticGM

@Override

public boolean onKeyDown(int keyCode, KeyEvent event) {
switch (keyCode) {
case KeyEvent.KEYCODE_BACK:
new AlertDialog.Builder(this)
.setTitle("注意！")
.setMessage("确定要残忍的退出吗？")
.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
Toast.makeText(getApplication(), "小仔，有种放学别走！", Toast.LENGTH_SHORT).show();
}
})
.setNegativeButton("取消", new DialogInterface.OnClickListener() {

@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
Toast.makeText(getApplication(), "老夫早就料到你会玩的！", Toast.LENGTH_SHORT).show();
}
}).create().show();
break;
}
//return super.onKeyDown(keyCode, event);
return false;
}