其实可以理解Handler为主线程和另外的线程之间进行数据更新的东东，并且Handler在主线程中，并在Handler直接调用线程的run方法
package com.Handler02;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
public class Handler02Activity extends Activity {
/** Called when the activity is first created. */
private Handler handler=new Handler();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
handler.post(thread1);
setContentView(R.layout.main);
System.out.println("================Main==============="+Thread.currentThread().getId());
System.out.println("============Main========="+Thread.currentThread().getName());
}
Runnable thread1=new Runnable() {
@Override
public void run() {
System.out.println("======thread1==============="+Thread.currentThread().getId());
System.out.println("========thread1============"+Thread.currentThread().getName());
try {
Thread.sleep(10000);
} catch (Exception e) {
// TODO: handle exception
}
}
};
}
结果是主线程等待10s后才显示出来，并且线程ID
package com.Handler4;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.TextView;
public class Handler4Activity extends Activity {
/** Called when the activity is first created. */
private TextView textView;
private MyHandler myHandler=new MyHandler();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textView=(TextView)this.findViewById(R.id.textView1);
}
class MyHandler extends Handler{
//从消息队列中取出并handleMessage处理消息
@Override
public void handleMessage(Message msg) {
textView.setText((String)msg.obj);
}
}
public void download(View view){
Thread thread=new Thread(new Runnable() {
@Override
public void run() {
try {
String s="zhangzhao";
Thread.sleep(5000);
//数据发送出来
//textView.setText(s);
Message message=Message.obtain();//最好不要new，这个obtain会节省资源
message.obj=s;
myHandler.sendMessage(message);//没有指定looper那么就会发送给主线程中的looper
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
thread.start();//会出错原因是在非UI线程里面直接操作UI
//主线程维护了一个消息对列，当其他的线程有数据需要传递给主线程的时候，你就把数据封装成一个Message对象，然后放在主线程的
//消息队列中去，对应消息的处理由Looper，子线程通过Handler把下载完的数据封装到Message里面，然后把消息取出来交给Handler进行处理
//通过Handle和Message实现两个线程之间达到共享数据
}
}
package com.Handler5;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
public class Handler5Activity extends Activity {
/** Called when the activity is first created. */
private ProgressBar progressBar;
private Button button;
private TextView textView;
private MyHandler myHandler=new MyHandler();
int i=0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
progressBar = (ProgressBar)this.findViewById(R.id.progressBar1);
textView=(TextView)this.findViewById(R.id.textView1);
}
class MyHandler extends Handler{
@Override
public void handleMessage(Message msg) {
int pos =(Integer)msg.obj;
progressBar.setProgress(pos);
textView.setText(pos+"%");
}
}
public void downLoad(View view){
new Thread(new Runnable() {
@Override
public void run() {
while(i<=100){
try {
Thread.sleep(300);
i+=10;
Message message=Message.obtain();
message.obj=i;
myHandler.sendMessage(message);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}).start();
}
}
效果：
