标签：
直接在UI线程中开启子线程来更新TextView显示的内容，运行程序我们会发现，如下错误：android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.翻译过来就是：只有创建这个控件的线程才能去更新该控件的内容。
所有的UI线程要去负责View的创建并且维护它，例如更新冒个TextView的显示，都必须在主线程中去做，我们不能直接在UI线程中去创建子线程，要利用消息机制：handler
public class HandlerTestActivity extends Activity {
private TextView tv;
private static final int UPDATE = 0;
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO 接收消息并且去更新UI线程上的控件内容
if (msg.what == UPDATE) {
// Bundle b = msg.getData();
// tv.setText(b.getString("num"));
tv.setText(String.valueOf(msg.obj));
}
super.handleMessage(msg);
}
};
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tv = (TextView) findViewById(R.id.tv);
new Thread() {
@Override
public void run() {
// TODO 子线程中通过handler发送消息给handler接收，由handler去更新TextView的值
try {
for (int i = 0; i < 100; i++) {
Thread.sleep(500);
Message msg = new Message();
msg.what = UPDATE;
// Bundle b = new Bundle();
// b.putString("num", "更新后的值：" + i);
// msg.setData(b);
msg.obj = "更新后的值：" + i;
handler.sendMessage(msg);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}.start();
}
}
我们就通过Handler机制来处理了子线程去更新UI线程控件问题，Andrid开发中要经常用到这种机制。
标签：
原文地址：http://my.oschina.net/carbenson/blog/520911
