Android：用定时器刷 timer 新界面

来源：互联网发布：中国瓷器品牌知乎编辑：程序博客网时间：2024/05/01 10:38

Android：用定时器刷 timer 新界面

在 Android 平台上，界面元素不能在定时器的响应函数里刷新。

以下这段代码中，mButton 的文本并不变化。

public class AndroidTimerDemo extends Activity {    private Button mButton;    private Timer mTimer;    private TimerTask mTimerTask;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        mButton = (Button) findViewById(R.id.Button01);        mTimer = new Timer();        mTimerTask = new TimerTask() {            @Override            public void run() {                Log.d("AndroidTimerDemo", "timer");                Calendar cal = Calendar.getInstance();                mButton.setText(cal.toString());            }        };        mTimer.schedule(mTimerTask, 1000, 1000);    }}

在 Android 平台上，UI 单元必须在 Activity 的 context 里刷新。为了达到想要的效果，可以使用 Message Handler。在定时器响应函数里发送条消息，在 Activity 里响应消息并更新文本。

public class AndroidTimerDemo extends Activity {    protected static final int UPDATE_TEXT = 0;    private Button mButton;    private Timer mTimer;    private TimerTask mTimerTask;    private Handler mHandler;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        mButton = (Button) findViewById(R.id.Button01);        mTimer = new Timer();        mHandler = new Handler(){            @Override            public void handleMessage(Message msg) {                switch (msg.what){                case UPDATE_TEXT:                    Calendar cal = Calendar.getInstance();                    mButton.setText(cal.toString());                    break;                }            }        };        mTimerTask = new TimerTask() {            @Override            public void run() {                Log.d("AndroidTimerDemo", "timer");                mHandler.sendEmptyMessage(UPDATE_TEXT);/*                              // It doesn't work updating the UI inside a timer.                Calendar cal = Calendar.getInstance();                mButton.setText(cal.toString());*/                          }        };        mTimer.schedule(mTimerTask, 1000, 1000);    }}