android监听返回按钮事件

  用户在点击手机的返回按钮时，默认是推出当前的activty，但是有时用户不小心按到返回，所以需要给用户一个提示，这就需要重写onkeydown事件，实现的效果如下：

实现代码如下：

@Override    
    public void onCreate(Bundle savedInstanceState) {     
        super.onCreate(savedInstanceState);     
        setContentView(R.layout.main);     
    }     
    protected void dialog() {     
        AlertDialog.Builder builder = new Builder(HanderTestActivty.this);     
        builder.setMessage("确定要退出吗?");     
        builder.setTitle("提示");     
        builder.setPositiveButton("确认",     
                new android.content.DialogInterface.OnClickListener() {     
                    @Override     
                    public void onClick(DialogInterface dialog, int which) {     
                        dialog.dismiss();     
                        HanderTestActivty.this.finish();     
                    }     
                });     
        builder.setNegativeButton("取消",     
                new android.content.DialogInterface.OnClickListener() {     
                    @Override     
                    public void onClick(DialogInterface dialog, int which) {     
                        dialog.dismiss();     
                    }     
                });     
        builder.create().show();     
    }     
    @Override     
    public boolean onKeyDown(int keyCode, KeyEvent event) {      
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {       
            dialog();       
            return false;       
        }       
        return false;       
    }