android multi_thread多线程下载

MainActivity.java

package com.multi_thread.download;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
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.ProgressBar;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

	private Button btn_download;
	private ProgressBar progressBar;
	private MyHandler myHandler;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		btn_download = (Button) findViewById(R.id.button1);
		progressBar = (ProgressBar) findViewById(R.id.progressBar1);
		progressBar.setProgress(0);

		btn_download.setOnClickListener(this);
		myHandler = new MyHandler();
	}

	@Override
	public void onClick(View v) {
		if (v.getId() == R.id.button1) {
			MyThread thread = new MyThread();
			thread.start();
		}
	}

	class MyHandler extends Handler {
		@Override
		public void handleMessage(Message msg) {
			super.handleMessage(msg);
			Bundle bundle = msg.getData();

			Toast.makeText(MainActivity.this, bundle.get("name").toString(),
					Toast.LENGTH_SHORT).show();
		}

	}

	class MyThread extends Thread {
		@Override
		public void run() {
			callHandler("开始下载");
			progressBar.setProgress(0);
			try {
				URL url = new URL(
						"http://192.168.43.78:8080/MyWeb/only_one_sing.mp3");
				HttpURLConnection connection = (HttpURLConnection) url
						.openConnection();
				int filesize = connection.getContentLength();
				progressBar.setMax(filesize);
				InputStream input = connection.getInputStream();
				File file = new File(Environment.getExternalStorageDirectory()
						+ "/aaa/aa.mp3");// Environment.getExternalStorageDirectory()
				file.createNewFile();
				OutputStream output = new FileOutputStream(file);
				byte[] b = new byte[1024];

				int fenzise = filesize / 2;
				int sizemore = filesize % 2;

				MultiThread[] threads = new MultiThread[2];
				for (int i = 0; i < threads.length; i++) {
					MultiThread thread = new MultiThread(url, file, i*fenzise, fenzise
							* (i + 1) - 1);
					thread.start();
					threads[i] = thread;
				}
				int count=0;
				boolean isfinished = true;
				while (isfinished) {
					// 先把整除的余数搞定
					count = sizemore;
					isfinished = false;
					for (int i = 0; i < threads.length; i++) {
						count += threads[i].getDownloadsize();
						if (!threads[i].isOk()) {
							isfinished = true;
						}
					}
					progressBar.setProgress(count);//更新下载进度
					// 休息1秒后再读取下载进度
					if(count==filesize){
						callHandler("下载结束");
						System.out.println("---------下载结束");
					}
					sleep(1000);
				}
				
			} catch (Exception e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
		}

		// 调用Handler
		private void callHandler(String str) {
			// TODO Auto-generated method stub
			Message message = new Message();
			Bundle data = new Bundle();
			data.putString("name", str);
			message.setData(data);
			MainActivity.this.myHandler.sendMessage(message);
		}
	}
}

MultiThread.java

package com.multi_thread.download;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.RandomAccessFile;
import java.net.URL;
import java.net.URLConnection;

public class MultiThread  extends Thread{
	
	private URL url;
	private File file;
	private int startPsittion;
	private int endPosition;
	private boolean isOk=false;// 用于标识当前线程是否下载完成
	
	private int downloadsize;
	
	public MultiThread(URL url,File file,int startPsittion,int endPosition) {
		this.url=url;
		this.file=file;
		this.startPsittion=startPsittion;
		this.endPosition=endPosition;
	}
	
	@Override
	public void run() {
		try {
			BufferedInputStream input=null;
			RandomAccessFile output=null;
			byte[] b=new byte[1024];
			URLConnection conn=url.openConnection();
			conn.setAllowUserInteraction(true);

			// 设置当前线程下载的起点，终点
			conn.setRequestProperty("Range","bytes="+startPsittion+"-"+endPosition);
			// 使用java中的RandomAccessFile 对文件进行随机读写操作
			output=new RandomAccessFile(file, "rw");
			// 设置开始写文件的位置
			output.seek(startPsittion);
			
			input=new BufferedInputStream(conn.getInputStream());
			int count=0;
			// 开始循环以流的形式读写文件
			while(count<endPosition){
				int length=input.read(b, 0, 1024);
				if(length==-1)
				break;
				
				output.write(b,0,length);//错误代码：output.write(b,0,1024);
				count+=length;
				
				if(count>endPosition){
					downloadsize+=length-(count-endPosition)+1;
				}else{
					downloadsize+=length;
				}
			}
			isOk=true;// 下载完成设为true
			input.close();
			output.close();						
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public boolean isOk() {
		return isOk;
	}
	
	public int getDownloadsize() {
		return downloadsize;
	}
	
	
}

activity_main.xml

<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" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="100dp"
        android:text="下载" />

    <ProgressBar
        android:id="@+id/progressBar1"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_marginTop="10dp"
        android:layout_below="@+id/button1" />

</RelativeLayout>

manifest.xml

    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.INTERNET"/>