public class MainActivity extends Activity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

    //点击物理按钮时，执行退出提示

public boolean onKeyDown(int keyCode,KeyEvent event){

    if(keyCode==KeyEvent.KEYCODE_BACK && event.getRepeatCount()==){

        creatdialog();

    }

    return false;

    }

private void creatdialog() {

    // TODO Auto-generated method stub

    AlertDialog.Builder b=new Builder(MainActivity.this);

    //设置提示框内容

    b.setMessage("确认退出么");

    //设置标题栏

    b.setTitle("提示");

    b.setPositiveButton("确认",new OnClickListener() {

        public void onClick(DialogInterface dialog, int which) {

            // TODO Auto-generated method stub

            //点确定时退出程序,并隐藏此对话框

            dialog.dismiss();

            MainActivity.this.finish();

        }

    }).setNegativeButton("取消",new OnClickListener() {

        @Override

        public void onClick(DialogInterface dialog, int which) {

            // TODO Auto-generated method stub

            //点击取消时只隐藏对话框

            dialog.dismiss();

        }

    });

    b.create().show();

    }

}