在Android中,如果你的应用有一段时间响应不够灵敏,系统会向用户显示一个称作为应用程序无响应(ANR:Application Not Responding)对话框。用户可以选择“等待”而让程序继续运行,也可以选择“强制关闭”。一个合理的APP中不能也不应该出现ANR。导致原因就是安卓UI主线程中不能进行耗时操作(网络请求,文件下载等),比如在android中Activity的最长执行时间是5秒,BroadcastReceiver的最长执行时间则是10秒,否则ANR就会不期而遇。这时我们就要用到异步处理工具。Handler主要是按计划发送消息或执行某个Runnanble,从非UI线程中发送来的消息放入消息队列中,然后通过处理消息更新UI线程)。
例子1,用Handler来更新UI线程:
- public class HandlerActivity extends Activity {
- public static final int HANDLER_MESSAGE = 1;
- private TextView mContentTv;
- @SuppressLint("HandlerLeak")
- private Handler mHandler = new Handler() {
- public void handleMessage(android.os.Message msg) {
- switch (msg.what) {
- case HANDLER_MESSAGE:
- mContentTv.setText("此时更新了数据");
- break;
- }
- };
- };
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- // TODO Auto-generated method stub
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
- mContentTv=(TextView) findViewById(R.id.t_title);
- }
- class myThread implements Runnable {
- public void run() {
- while (!Thread.currentThread().isInterrupted()) {
- Message message = new Message();
- message.what = HANDLER_MESSAGE;
- mHandler.sendMessage(message);
- try {
- Thread.sleep(100);
- } catch (InterruptedException e) {
- Thread.currentThread().interrupt();
- }
- }
- }
- }
- }
例子1,用Handler来完成定时(周期性)操作(当然可以用Timer,TimerTask及Android自带的AlarmManage):
- public class HandlerActivity extends Activity {
- private TextView mContentTv;
- private Handler handler = new Handler();
- private int mCounter = 0;
- private Runnable mRunnable = new Runnable() {
- public void run() {
- handler.postDelayed(this, 5000);// 5秒后操作
- mCounter++;
- mContentTv.setText("Count: " + mCounter);
- }
- };
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- // TODO Auto-generated method stub
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
- mContentTv = (TextView) findViewById(R.id.t_title);
- handler.post(mRunnable);
- }
- }
来源: http://www.phpxs.com/code/1002248/