36.Android之多线程和handle更新UI学习

android经常用到多线程更新UI，今天学习下.

首先布局比较简单：

<?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" >

    <ScrollView
        android:id="@+id/scrollView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

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

        </LinearLayout>
    </ScrollView>
    
 </LinearLayout>

增加一个读取文件线程类：

package com.example.mulitthreadactivitydemo;

import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.List;

import android.util.Log;

public class FileRead {

    boolean readend = false;
    List<String> al = null;
    private static final String Tag = "addfile";

    public class ReadNodesThread extends Thread {// 读取线程

        public void run() {
            al = new ArrayList<String>(100);
            al.clear();
            readend = false;
            int i = 0;
            try {
                String dirstr = "/storage/sdcard0/DCIM/test.txt";
                //RandomAccessFile raf = new RandomAccessFile("/sdcard/test.txt","r");
                RandomAccessFile raf = new RandomAccessFile(dirstr,"r");
                // try {
                while (raf.getFilePointer() < raf.length()) {
                    al.add(raf.readLine());
                    Log.i(Tag,"addfile = " + raf.readLine());
                    // sleep(100);//如果测试文件太小，这里休眠是为了测试，
                }

            } catch (Exception e1) {
                // TODO Auto-generated catch block      
                e1.printStackTrace();
            }
            readend = true;
        }
    };

}

最后修改下主类：

package com.example.mulitthreadactivitydemo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
  
public class MainActivity extends Activity {
    
    FileRead fr=null;
    Handler mHandler=null;
    int curi=0;
    Runnable updateui=null;
    String[] tmp=null;
    String s="";
    TextView tv=null;
    
    class ReadListener extends Thread{//监听线程，当数据更新数目大于10条时，更新UI

        public void run()
        {
            int i=0,newi=0;
            while(!fr.readend)
            {
                newi=fr.al.size();
                if((newi-i)>10)//新增数据大于10条，更新UI
                {
                    i=newi;
                    tmp=(String[])fr.al.toArray(new String[fr.al.size()]);
                    mHandler.post(updateui);
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
            //数据读完了
            tmp=(String[])fr.al.toArray(new String[fr.al.size()]);
            mHandler.post(updateui);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    };
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.tv);    
        fr=new FileRead();        
        FileRead.ReadNodesThread readThread = fr.new ReadNodesThread();
        updateui = new Runnable()//更新UI的线程
        {
            @Override
            public void run() {
                // TODO Auto-generated method stub

                int i=0;

                for(i=curi;i<tmp.length;i++)
                {
                    s+=tmp[i]+"
";
                }
                tv.setText(s);
                curi=i;
            }};
        readThread.start();
        ReadListener updateThread=new ReadListener();
        mHandler=new Handler();
        updateThread.start();
    
    }

}

运行效果：可以看到滚动条慢慢变短，则说明程序加载成功.