android 的Handler处理UI主线程外的耗时操作_android handler 处理耗时任务-优快云博客

本文介绍了一个使用Android Handler机制实现UI线程与工作线程间通信的例子。通过定义Handler实例处理来自工作线程的消息，更新UI显示成功或失败状态。文章展示了如何在Android应用中创建并启动一个新的线程来执行耗时任务，并利用Handler发送消息到主线程。

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package com.example.handlerdemowjj;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
// 另外的线程
private static final int MSG_SUCCESS = 0;// 获取成功的标识
private static final int MSG_FAILURE = 1;// 获取失败的标识
private Thread mThread;
TextView tv;

private Handler mHandler = new Handler(){

  public void handleMessage(Message msg) {// 此方法在ui线程运行
   switch (msg.what) {
   case MSG_SUCCESS:
    Log.v("logcat", "MSG_SUCCESS" + Thread.currentThread());
    Log.v("logcat", "MSG_SUCCESS_ID:"
      + Thread.currentThread().getId() + ",name="
      + Thread.currentThread().getName());
    Toast.makeText(getApplication(), "成功", Toast.LENGTH_LONG)
      .show();
    tv.setText("new.成功");
    break;

   case MSG_FAILURE:
    Log.v("logcat", "MSG_FAILURE" + Thread.currentThread());
    Toast.makeText(getApplication(), "失败", Toast.LENGTH_LONG)
      .show();
    break;
   }
  }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  tv = (TextView) findViewById(R.id.tv);

  Runnable runnable = new Runnable() {
   @Override
   public void run() {
    //这是新的线程，可在这儿处理耗时的操作，更新不了UI界面的操作的

    Log.v("logcat",
      "new-Thread.currentThread()=" + Thread.currentThread());
    Log.v("logcat", "new-Thread.currentThread().getId()="
      + Thread.currentThread().getId() + ",name="
      + Thread.currentThread().getName());

    int i = 0;
    if (i == 0) {
     mHandler.obtainMessage(MSG_SUCCESS).sendToTarget();// 获取成功

    } else {
     mHandler.obtainMessage(MSG_FAILURE).sendToTarget();// 获取失败
    }

   }
  };
  if (mThread == null) {

   Toast.makeText(getBaseContext(), "mThread == null",
     Toast.LENGTH_LONG).show();
   mThread = new Thread(runnable);
   mThread.start();// 线程启动
  } else {
   Toast.makeText(getBaseContext(), "thread_started",
     Toast.LENGTH_LONG).show();
  }

}