Android使用HttpURLConnection实现多线程下载
工具类代码:
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package com.example.xiaocool.multithreadclient; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; public class DownUtil { // 定义下载资源的路径 private String path; // 指定所下载的文件的保存位置 private String targetFile; // 定义需要使用多少线程下载资源 private int threadNum; // 定义下载的线程对象 private DownThread[] threads; // 定义下载的文件的总大小 private int fileSize; public DownUtil(String path, String targetFile, int threadNum) { this.path = path; this.threadNum = threadNum; // 初始化threads数组 threads = new DownThread[threadNum]; this.targetFile = targetFile; } public void download() throws Exception { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); conn.setRequestProperty( "Accept", "p_w_picpath/gif, p_w_picpath/jpeg, p_w_picpath/pjpeg, p_w_picpath/pjpeg, " + "application/x-shockwave-flash, application/xaml+xml, " + "application/vnd.ms-xpsdocument, application/x-ms-xbap, " + "application/x-ms-application, application/vnd.ms-excel, " + "application/vnd.ms-powerpoint, application/msword, */*"); conn.setRequestProperty("Accept-Language", "zh-CN"); conn.setRequestProperty("Charset", "UTF-8"); conn.setRequestProperty("Connection", "Keep-Alive"); // 得到文件大小 fileSize = conn.getContentLength(); conn.disconnect(); int currentPartSize = fileSize / threadNum + 1; RandomAccessFile file = new RandomAccessFile(targetFile, "rw"); // 设置本地文件的大小 file.setLength(fileSize); file.close(); for (int i = 0; i < threadNum; i++) { // 计算每条线程的下载的开始位置 int startPos = i * currentPartSize; // 每个线程使用一个RandomAccessFile进行下载 RandomAccessFile currentPart = new RandomAccessFile(targetFile, "rw"); // 定位该线程的下载位置 currentPart.seek(startPos); // 创建下载线程 threads[i] = new DownThread(startPos, currentPartSize, currentPart); // 启动下载线程 threads[i].start(); } } // 获取下载的完成百分比 public double getCompleteRate() { // 统计多条线程已经下载的总大小 int sumSize = 0; for (int i = 0; i < threadNum; i++) { sumSize += threads[i].length; } // 返回已经完成的百分比 return sumSize * 1.0 / fileSize; } private class DownThread extends Thread { // 当前线程的下载位置 private int startPos; // 定义当前线程负责下载的文件大小 private int currentPartSize; // 当前线程需要下载的文件块 private RandomAccessFile currentPart; // 定义已经该线程已下载的字节数 public int length; public DownThread(int startPos, int currentPartSize, RandomAccessFile currentPart) { this.startPos = startPos; this.currentPartSize = currentPartSize; this.currentPart = currentPart; } @Override public void run() { try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection)url .openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); conn.setRequestProperty( "Accept", "p_w_picpath/gif, p_w_picpath/jpeg, p_w_picpath/pjpeg, p_w_picpath/pjpeg, " + "application/x-shockwave-flash, application/xaml+xml, " + "application/vnd.ms-xpsdocument, application/x-ms-xbap, " + "application/x-ms-application, application/vnd.ms-excel, " + "application/vnd.ms-powerpoint, application/msword, */*"); conn.setRequestProperty("Accept-Language", "zh-CN"); conn.setRequestProperty("Charset", "UTF-8"); InputStream inStream = conn.getInputStream(); // 跳过startPos个字节,表明该线程只下载自己负责哪部分文件。 inStream.skip(this.startPos); byte[] buffer = new byte[1024]; int hasRead = 0; // 读取网络数据,并写入本地文件 while (length < currentPartSize && (hasRead = inStream.read(buffer)) > 0) { currentPart.write(buffer, 0, hasRead); // 累计该线程下载的总大小 length += hasRead; } currentPart.close(); inStream.close(); } catch (Exception e) { e.printStackTrace(); } } } }
MainActivity:
package com.example.xiaocool.multithreadclient; import android.os.Handler; import android.os.Message; import android.support.v7.app.ActionBarActivity; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.ProgressBar; import java.util.Timer; import java.util.TimerTask; public class MainActivity extends ActionBarActivity { EditText url; EditText target; Button downBn; ProgressBar bar; DownUtil downUtil; private int mDownStatus; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); url = (EditText) findViewById(R.id.url); target = (EditText) findViewById(R.id.target); downBn = (Button) findViewById(R.id.down); bar = (ProgressBar) findViewById(R.id.bar); // 创建一个Handler对象 final Handler handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what == 0x123) { bar.setProgress(mDownStatus); } } }; downBn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // 初始化DownUtil对象 最后一个参数指定线程数 downUtil = new DownUtil(url.getText().toString(), target.getText().toString(), 6); new Thread() { @Override public void run() { try { // 开始下载 downUtil.download(); } catch (Exception e) { e.printStackTrace(); } // 定义美妙调度获取一次系统的完成进度 final Timer timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { // 获取下载任务的完成比例 double completeRate = downUtil.getCompleteRate(); mDownStatus = (int) (completeRate * 100); handler.sendEmptyMessage(0x123); // 下载完成后取消任务调度 if (mDownStatus >= 100) { timer.cancel(); } } }, 0, 100); } }.start(); } }); } }
新闻名称:Android使用HttpURLConnection实现多线程下载
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