安卓开发退出程序时询问是否确定退出

效果图如图： 

在MainActivity中加几句话即可：

AlertDialog builder=null;

  @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK){
            builder = new AlertDialog.Builder(MainActivity.this)
                    .setTitle("温馨提示：")
                    .setMessage("您是否要退出程序？")
                    .setPositiveButton("确定",
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                                    int whichButton) {
                                    MainActivity.this.finish();
                                }
                            })
                    .setNegativeButton("取消",
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog,
                                                    int whichButton) {
                                    builder.dismiss();
                                }
                            }).show();
        }
        return true;
    }