.Net程序员玩转Android开发---(17)Handler用法

         在android开发中，如果在一个线程中想更新主界面中控件显示的数据，直接给主界面控件赋值就会出现异常，android中为了安全起见，是不允许在线程中更新界面控件的数据，遇到这种情况，我们可以使用Handler.  Handler就是处理界面和线程间的消息传递，通信的组件。下面我们演示下handler处理详细的两种办法,下面的这个列子通过点击不同按钮展现handler.post和handler.sendmsg两个传递消息的方法。

        

        1. Handler.Post

                      创建一个handler对象和Runnable对象，通过handler.post(new Runnable(){});处理来更新界面中的textview的数据

        2.Handler.sendMessage

              这个例子中，我们创建一个employee员工类，单击按钮的时候，显示员工的信息，通过handler.sendmessage来传递消息和参数进行处理

                全部代码

                 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textViewMsg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

    <Button
        android:id="@+id/btnpost"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="handler post" />

    <Button
        android:id="@+id/btnmsg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="handler message" />
    
</LinearLayout>

package com.example.helloword;



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

public class HandlerActivity extends Activity {

	
	private TextView tv;
	
	private Button btnpost;
	
	private Button btnmsg;
	
	private Handler handler=new Handler();//post处理handler
	
	//sendmsg处理handler
	private Handler handlerTwo=new Handler(){
		
		public void handleMessage(Message msg) {
			
			switch (msg.what) {
			case 0:
				tv.setText("姓名:"+((employee)msg.obj).name);
				break;
			
			}

		}
	};
	
	protected void onCreate(Bundle savedInstanceState) 
	{
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.handlerlayout);
		tv=(TextView)findViewById(R.id.textViewMsg);
		
		btnpost=(Button)findViewById(R.id.btnpost);
		btnmsg=(Button)findViewById(R.id.btnmsg);
		
		btnpost.setOnClickListener(new OnClickListener(){

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				Thread thread=new Thread(new Runnable()
				{

					@Override
					public void run() {
						// TODO Auto-generated method stub
						handler.post(runOne);
					}
				}
				);
				
				thread.start();
			}
		});
		
		
		btnmsg.setOnClickListener(new OnClickListener(){

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				Thread thread=new Thread(new Runnable()
				{
					@Override
					public void run() {
						// TODO Auto-generated method stub
						Message msg=new Message();
						msg.arg1=1;
						
						employee employeeone=new employee();
						employeeone.name="员工1";
						employeeone.age=20;
						msg.obj=employeeone;
						msg.what=0;
						
						handlerTwo.sendMessage(msg);
					}
				}
				);
				
				thread.start();
			}
		});
	
	}
	
	
    Runnable  runOne=new Runnable(){
		@Override
		public void run() {
			// TODO Auto-generated method stub
			tv.setText("正在执行handler post");
		}
    };
    
    
    public class employee
    {
    	  public String name;
    	  public int age;
    }
}