android handler 线程机制的研究-优快云博客

先来看一段代码：

package com.my; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Log; public class DemoActivity extends Activity { private final static int MESSAGE=1; Handler handler=new Handler() { @Override public void handleMessage(Message msg) { // TODO Auto-generated method stub super.handleMessage(msg); switch(msg.what) { case MESSAGE: Log.e("222", Thread.currentThread().getId()+"--->"+Thread.currentThread().getName()); } } }; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.main); Log.e("111", Thread.currentThread().getId()+"--->"+Thread.currentThread().getName()); Message msg=new Message(); msg.what=MESSAGE; handler.sendMessage(msg); } }

在这段代码中打印出如下log：

可以看出，handler和主程序都运行在主线程里面，如果要想让handler运行在不同的线程里面，就需要重新启动一个线程，代码如下：

package com.my; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.util.Log; public class DemoActivity extends Activity { private final static int MESSAGE = 1; Handler handler = new Handler() { @Override public void handleMessage(Message msg) { // TODO Auto-generated method stub super.handleMessage(msg); switch (msg.what) { case MESSAGE: Thread thread = new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub Log.e("333", Thread.currentThread().getId() + "--->" + Thread.currentThread().getName()); } }); thread.start(); Log.e("222", Thread.currentThread().getId() + "--->" + Thread.currentThread().getName()); } } }; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.main); Log.e("111", Thread.currentThread().getId() + "--->" + Thread.currentThread().getName()); Message msg = new Message(); msg.what = MESSAGE; handler.sendMessage(msg); } }

运行后的log如下：