Android专题3——MainThread向WorkerThread通信

Android一般WorkerThread不能改变UI进程（MainThread）

所以需要Handler

点击数据按钮，启动一个线程，模拟从网上获得数据

点击以后，过一秒钟后改变TextView内容

首先给Button绑定一个监听器，让其创建一个线程

这个线程模拟从网络中获得数据

Handler定义如何处理

package com.njulya.testhandler;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {
    private Handler handler;
    private TextView text ;
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        text = (TextView)findViewById(R.id.textId);
        button = (Button)findViewById(R.id.buttonId);
        button.setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View arg0) {
                NetworkThread nt = new NetworkThread();
                nt.start();
            }
        });
        
        handler = new Handler(){
            @Override
            public void handleMessage(Message msg){
                String str = (String)msg.obj;
                text.setText(str);
            }
        };
    }

    private class NetworkThread extends Thread{
        @Override
        public void run(){
            try {
                sleep(2*1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            Message msg = handler.obtainMessage();
            msg.obj = "从网络获得的数据";
            handler.sendMessage(msg);
        }
    }

    @Override
    public 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;
    }
    
}

<RelativeLayout 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: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/textId"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
    
    <Button 
        android:id="@+id/buttonId"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/textId"
        android:text="数据"/>

</RelativeLayout>