Android(安卓)Handler Message 通信机制

Android UI线程更新并不是线程安全的，并且必须在UI线程中进程UI更新操作，以下面一个错误为例：

public class MainActivity extends Activity {private String title;private Button btn;private final Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {setTitle(title);}};@Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        btn = (Button) findViewById(R.id.time);        btn.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) { Timer timer = new Timer();         timer.schedule(new MyTask(), 1000);}});}class MyTask extends TimerTask{Message msg;Bundle bundle;SimpleDateFormat sdf;public MyTask(){Message msg = new Message();Bundle bundle = new Bundle();sdf = new SimpleDateFormat();}@Overridepublic void run() {String date = sdf.format(new Date());//在子线程中更新UI                        setTitle("当前时间 ："+date);}}}

上面的例子会报 “Only the original thread that created a view hierarchy can touch its views.”

正确的写法应该是在子线程中组装数据，然后通过handler发送消息给UI线程，最后在UI线程中更新UI：

public class MainActivity extends Activity {private Button btn;private final Handler handler = new Handler(){@Overridepublic void handleMessage(Message msg) {//接收消息switch (msg.what) {case 110:Bundle bundle = msg.getData();String date = bundle.getString("date");//更新UIsetTitle(date);break;}}};@Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        btn = (Button) findViewById(R.id.time);        btn.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) { Timer timer = new Timer(); //设置每秒执行一次     timer.schedule(new MyTask(),0,1000);}});}class MyTask extends TimerTask{Message msg;Bundle bundle;SimpleDateFormat sdf;public MyTask(){msg = new Message();bundle = new Bundle();sdf = new SimpleDateFormat("yyyy年MM月dd : HH时mm分ss");}@Overridepublic void run() {//组装数据String date = sdf.format(new Date());msg.what = 110;bundle.putString("date", date);msg.setData(bundle);//发送消息handler.sendMessage(msg);}}}

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