Handler使用方法总结

在看这篇博客之前，最好看看《Anroid异步消息机制（Handler、Looper、Message、MessageQueue）以及ThreadLocal运用》了解Handler原理。

Handler使用，主要有以下几种方式：

Thread+Handler、Timer+TimerTask+Handler、Handler.postXXX(Runnable r,...)、Handler.sendXXX()、AsyncTask。

1、activity_handler.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <TextView        android:id="@+id/handler_post_text"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="handler.post()" />    <TextView        android:id="@+id/timer_handler_text"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Timer+TimerTask+Handler" />        <TextView        android:id="@+id/thread_handler_text"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="thread+handler" />           <TextView        android:id="@+id/asyncTask_text"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="asyncTask" />         <Button        android:id="@+id/thread_handler_button"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="thread+handler" />             <Button        android:id="@+id/asyncTask_button"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="asyncTask" /></LinearLayout>

2、HandlerExample.java

import java.lang.ref.WeakReference;import java.util.Timer;import java.util.TimerTask;import android.app.Activity;import android.os.AsyncTask;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.os.SystemClock;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;public class HandlerExample extends Activity {private TextView handler_post_text = null;private TextView timer_handler_text = null;private TextView thread_handler_text = null;private TextView asyncTask_text = null;private Button thread_handler_button = null;private Button asyncTask_button =null;private Handler handler;private Timer timer;private AsyncTask asyncTask;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_handler);//WeakReference<Handler> wf = new WeakReference<Handler>(new MyHandler());//handler = (wf != null) ? wf.get() : null;handler = new MyHandler();timer = new Timer();timer.schedule(new MyTimer(), 1, 5000);handler_post_text = (TextView) findViewById(R.id.handler_post_text);timer_handler_text = (TextView) findViewById(R.id.timer_handler_text);thread_handler_text = (TextView) findViewById(R.id.thread_handler_text);asyncTask_text = (TextView) findViewById(R.id.asyncTask_text);thread_handler_button = (Button) findViewById(R.id.thread_handler_button);asyncTask_button = (Button) findViewById(R.id.asyncTask_button);thread_handler_button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {new Thread(new Runnable() {@Overridepublic void run() {Message message = new Message();message.what = 2;handler.sendMessage(message);// handler.sendEmptyMessage(int what);// handler.sendEmptyMessageAtTime(int what, long uptimeMillis);//什么时间执行发送消息// handler.sendEmptyMessageDelayed(int what, long delayMillis);//延迟多少执行发送消息// handler.sendMessageAtTime(Message msg, long uptimeMillis);//什么时间执行发送消息// handler.sendMessageDelayed(Message msg, long uptimeMillis);//延迟多少执行发送消息}}).start();}});asyncTask_button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {asyncTask = new MyAsyncTask();//需要在UI线程中进行asyncTask.execute("hello world");//需要在UI线程中进行//asyncTask.execute(Runnable runnable);//asyncTask.execute(Object o);//asyncTask.execute(Object... params);}});handler.postAtTime(new Runnable() {@Overridepublic void run() {handler_post_text.setText("MainActivity.handler_post."+ Thread.currentThread().getName() + "-"+ Thread.currentThread().getId());}}, handler_post_text, SystemClock.uptimeMillis() + 4000);// 默认Message// handler.post(Runnable r);// handler.postAtTime(Runnable r, long uptimeMillis);//什么时间执行发送消息// handler.postDelayed(Runnable r, long uptimeMillis);//延迟多少执行发送消息}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}// 设置定时器任务class MyTimer extends TimerTask {@Overridepublic void run() {Message message = new Message();message.what = 1;handler.sendMessage(message);}}//onPreExecute->doInBackground->onProgressUpdate(需要doInBackground调用了publishProgress才能通过Handler触发)->onPostExecute(可无)//第一个参数是execute方法、doInBackground方法参数类型；//第二个参数是onProgressUpdate方法的参数类型；//第三个参数是onPostExecute方法的参数类型以及doInBackground返回参数类型class MyAsyncTask extends AsyncTask<Object, Integer, String>{@Overrideprotected void onPreExecute(){//可以ui更新asyncTask_text.setText("MainActivity.asyncTask."+ Thread.currentThread().getName() + "-"+ Thread.currentThread().getId());}@Overrideprotected String doInBackground(Object... arg0) {//可以执行耗时的任务，因而不能执行ui更新return "AsyncTask";}@Overrideprotected void onProgressUpdate(Integer... progresses){}@Overrideprotected void onPostExecute(String result){//更新ui，显示结果asyncTask_text.setText("AsyncTask");}@Overrideprotected void onCancelled(){//取消执行任务时，更新ui}}final class MyHandler extends Handler {@Overridepublic void handleMessage(Message message) {if (message.what == 1) {timer_handler_text.setText("MainActivity.timer_handler."+ Thread.currentThread().getName() + "-"+ Thread.currentThread().getId());} else if (message.what == 2) {thread_handler_text.setText("MainActivity.thread_handler."+ Thread.currentThread().getName() + "-"+ Thread.currentThread().getId());}}}@Overrideprotected void onStop() {super.onStop();}@Overrideprotected void onDestroy() {super.onDestroy();if (timer != null) {timer.cancel();}if (handler != null) {handler.removeCallbacksAndMessages(null);// 释放Handler}}@Overrideprotected void onResume() {super.onResume();}}

3、AsyncTask

对Thread+Handler进行包装，更加流程化来处理UI。概括来说，当我们在UI线程中调用execute()方法后会调用onPreExecute()方法，然后由ThreadPoolExecutor实例sExecutor执行一个FutureTask任务，这个过程中doInBackground()方法将被调用，如果被开发者覆写的doInBackground()方法中调用了publishProgress()方法，则通过InternalHandler实例sHandler发送一条MESSAGE_POST_PROGRESS消息，更新进度；sHandler处理消息时onProgressUpdate()方法将被调用；如果遇到异常，则发送一条MESSAGE_POST_CANCEL的消息，取消任务，sHandler处理消息时onCancelled()方法将被调用；如果执行成功，则发送一条MESSAGE_POST_RESULT的消息，显示结果，sHandler处理消息时onPostExecute(Result result)方法被调用。

如下图所示：