一、整体工程图
二、activity_handler.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"> <Button android:text="Handler Lab1" android:id="@+id/buttonHandlerLab1" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
<Button android:text="Handler Lab2" android:id="@+id/buttonHandlerLab2" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
<Button android:text="Handler Lab3" android:id="@+id/buttonHandlerLab3" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
<Button android:text="Handler Lab4.1" android:id="@+id/buttonHandlerLab4_1" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
<Button android:text="Handler Lab4.2" android:id="@+id/buttonHandlerLab4_2" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
<Button android:text="Handler Lab5.1" android:id="@+id/buttonHandlerLab5_1" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
<Button android:text="Handler Lab5.2" android:id="@+id/buttonHandlerLab5_2" android:layout_width="fill_parent" android:layout_height="wrap_content"></Button>
</LinearLayout>
三、HandlerActivity.java
package com.jltxgcy.handlerdemo; import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Toast;
import android.os.Process; public class HandlerActivity extends Activity {
private static final String TAG="jltxgcy";
private final String HANDLER_KEY = "jltxgcy" ;
private Handler lab1Handler1 ;
private Handler lab1Handler2 ;
private Handler lab2Handler ;
private Handler lab3Handler;
private Handler lab4Handler;
private Handler lab5_1Handler = new Handler();
private Handler lab5_2Handler;
private Looper mLooper;
private String result;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_handler);
lab1Handler2 = new Handler(){ @Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
Toast.makeText(HandlerActivity.this, "[Main Thread]Handler2 Get the message: "+msg.getData().getString(HANDLER_KEY), 5000).show() ;
} } ;
lab1Handler1 = new Handler(){ @Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
result=msg.getData().getString(HANDLER_KEY);
Toast.makeText(HandlerActivity.this, "[Main Thread]Handler1 Get the message: "+msg.getData().getString(HANDLER_KEY), 5000).show() ;
} } ; //Handler Lab1
findViewById(R.id.buttonHandlerLab1).setOnClickListener(new OnClickListener(){ @Override
public void onClick(View v) {
new Thread(new Runnable(){ @Override
public void run() { lab1Handler1.sendMessage(defineNewMessage("Lab1")) ;
//try to use mainHanlder2 to send meesage and receive .
//mainHandler2.sendMessage(defineNewMessage("Lab1")) ; } }).start(); } }) ; findViewById(R.id.buttonHandlerLab2).setOnClickListener(new OnClickListener() { @Override
public void onClick(View v) {
new Thread(new Runnable(){ @Override
public void run() {
lab2Handler = new Handler(Looper.getMainLooper())
{ @Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
Log.d(TAG, "Get the message: "+msg.getData().getString(HANDLER_KEY)+" by Child Thread Handler") ;
} };
lab2Handler.sendMessage(defineNewMessage("Lab2")) ;
lab3Handler.sendMessage(defineNewMessage("Lab3")) ; } }).start() ; }
}); findViewById(R.id.buttonHandlerLab3).setOnClickListener(new OnClickListener() { @Override
public void onClick(View v) {
new Thread(new Runnable(){ @Override
public void run() {
// TODO Auto-generated method stub
Looper.prepare();
lab3Handler = new Handler(){ @Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
Log.d(TAG, "Get the message from "+msg.getData().getString(HANDLER_KEY)+" by Child Thread Handler") ;
}
} ;
Looper.loop();
} }).start() ; }
}); findViewById(R.id.buttonHandlerLab4_1).setOnClickListener(new OnClickListener() { @Override
public void onClick(View v) {
HandlerThread thread = new HandlerThread("ServiceStartArguments",
Process.THREAD_PRIORITY_BACKGROUND);
thread.start(); // Get the HandlerThread's Looper and use it for our Handler
mLooper = thread.getLooper();
lab4Handler = new Handler(mLooper){
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
Log.d(TAG, "Start message "+msg.getData().getString(HANDLER_KEY)+" by Child Thread Handler") ;
try {
Thread.sleep(5*1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.d(TAG, "Finish message "+msg.getData().getString(HANDLER_KEY)+" by Child Thread Handler");
}
};
lab4Handler.sendMessage(defineNewMessage("Lab4.1")) ;
lab4Handler.sendMessage(defineNewMessage("Lab4.2")) ; }
}); findViewById(R.id.buttonHandlerLab4_2).setOnClickListener(new OnClickListener() { @Override
public void onClick(View v) {
lab4Handler.removeMessages(1); }
}); findViewById(R.id.buttonHandlerLab5_1).setOnClickListener(new OnClickListener() { @Override
public void onClick(View v) {
lab5_1Handler.postDelayed(new MyRunnable(), 2000);
Log.d(TAG, ""+Thread.currentThread().getId());
}
}); findViewById(R.id.buttonHandlerLab5_2).setOnClickListener(new OnClickListener() { @Override
public void onClick(View v) {
HandlerThread handlerThread = new HandlerThread("myHandlerThread");
handlerThread.start();
lab5_2Handler = new Handler(handlerThread.getLooper());
lab5_2Handler.post(new MyRunnable());
Log.d(TAG,""+Thread.currentThread().getId());
}
});
} private class MyRunnable implements Runnable {
public void run() {
Log.d(TAG, "Runnable---The Thread is running");
Log.d(TAG, ""+Thread.currentThread().getId());
}
} private Message defineNewMessage(String messageContent)
{
Message returnMsg = new Message() ;
Bundle data = new Bundle() ;
data.putString(HANDLER_KEY, messageContent) ;
returnMsg.setData(data) ;
returnMsg.what=1;
return returnMsg ;
}
}
四、解析
Handler Lab1，接受消息的Handler在主线程中定义，而且处理消息也在主线程中。发送消息在子线程中。
Handler Lab2，接受消息的Handler在子线程中定义，而处理消息却在主线程中。发送消息在子线程中。
Handler Lab3，接受消息的Handler在子线程中定义，而且处理消息也在子线程中。发送消息在主线程中。
Hander Lab4_1，接受消息的Handler在主线程中定义，而处理消息却在子线程中。发送消息在主线程中。
Hander Lab4_2，连续发送两条信息，结果如下，说明是一条信息结束后，才处理另一个信息。
如果在发送第一个消息没有Finish前，按下Hander Lab4_2，那么第一个消息不会取消，第二个消息会取消。
Hander Lab5_1，延迟2秒钟，开启run中的方法。结果显示如下，说明没有开启新的线程。
Hander Lab5_2，结果显示如下，这回开启了新的线程。
1、Hander子线程用于每隔多长时间，或者完成一项任务向主线程发送消息，主线程接受消息后，更新UI。
2、Hander主线程负责向子线程发送消息，子线程接受消息后开始下载。
3、postDelay用于比如闹钟要隔几分钟后启动。
五、Message
获取Message的两种方式，第一种比较易读，第二种比较简洁。
1、Message msg =new Message();
msg.arg1=x;
msg.arg2=x;
msg.obj=x;
msg.replyTo=x;
msg.what=x;
msg.setData(Bundle bundle);
2、Message msg =Handler.obtain(Handler h, int what, int arg1, int arg2, Object obj);
msg.replyTo=x;
msg.setData(Bundle bundle);