android HttpURLConnection实现多线程下载
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使用HttpURLConnection实现多线程下载
分类: Android 2013-07-17 01:03 1809人阅读 评论(2)收藏 举报
AndroidHttpURLConnection多线程下载
HttpURLConnection继承了URLConnection,因此也可用于向指定网站发送GET请求、POST请求,而且它在URLConnection基础上提供了如下便捷方法:
实现多线程下载的步骤:
下面用一个示例来示范使用HttpURLConnection实现多线程下载。此代码来源疯狂讲义一书,该代码主要思路:在Activity中点击按钮,调用DownUtil的download()方法,在download()中启动四个线程去下载资源,每个线程负责下载自己的那部分资源,代码如下:
Activity:
- package com.home.activity;
- import java.util.Timer;
- import java.util.TimerTask;
- 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.EditText;
- import android.widget.ProgressBar;
- import com.home.multithreaddown.R;
- import com.home.util.DownUtil;
- public class MultiThreadDownActivity extends Activity {
- private EditText urlText;
- private EditText targetText;
- private Button downBtn;
- private ProgressBar bar;
- private DownUtil downUtil;
- private int mDownStatus;
- private Handler handler;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- // 获取界面中控件
- targetText = (EditText) findViewById(R.id.main_et_name);
- urlText = (EditText) findViewById(R.id.main_et_url);
- downBtn = (Button) findViewById(R.id.main_btn_download);
- bar = (ProgressBar) findViewById(R.id.main_progressBar);
- // 创建一个Handler对象
- handler = new Handler() {
- public void handleMessage(Message msg) {
- if (msg.what == 0x123) {
- bar.setProgress(mDownStatus);
- }
- }
- };
- downBtn.setOnClickListener(new OnClickListener() {
- @Override
- public void onClick(View v) {
- // 初始化DownUtil对象
- downUtil = new DownUtil(urlText.getText().toString(),
- targetText.getText().toString(), 4);
- try {
- // 开始下载
- downUtil.download();
- } catch (Exception e) {
- e.printStackTrace();
- }
- // 定义每秒调度获取一次系统的完成进度
- final Timer timer = new Timer();
- timer.schedule(new TimerTask() {
- public void run() {
- // 获取下载任务的完成比率
- double completeRate = downUtil.getCompleteRate();
- mDownStatus = (int) (completeRate * 100);
- // 发送消息通知界面更新进度条
- handler.sendEmptyMessage(0x123);
- // 下载完成后取消任务调度
- if (mDownStatus >= 100) {
- timer.cancel();
- }
- }
- }, 0, 100);
- }
- });
- }
- }
下载的工具类(DownUtil):
- package com.home.util;
- 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;
- // 定义下载的文件的总大小
- private int fileSize;
- // 定义下载的线程对象
- private DownloadThread[] threads;
- public DownUtil(String path, String targetFile, int threadNum) {
- this.path = path;
- this.threadNum = threadNum;
- // 初始化threads数组
- threads = new DownloadThread[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",
- "image/gif,image/jpeg,image/pjpeg,application/x-shockwaveflash,application/x-ms-xbap,application/xaml+xml,application/vnd.ms-xpsdocument,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(
- "User-Agent",
- "Mozilla/4.0(compatible;MSIE7.0;Windows NT 5.2;Trident/4.0;.NET CLR 1.1.4322;.NET CLR 2.0.50727;.NET CLR 3.0.04506.30;.NET CLR 3.0.4506.2152;.NET CLR 3.5.30729)");
- 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 DownloadThread(startPos, currentPartSize,
- currentPart);
- // 启动下载线程
- threads[i].start();
- }
- }
- /**
- * 获取下载完成的百分比
- *
- * @return
- */
- 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 DownloadThread 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;
- // 定义该线程已下载的字节数
- private int length = 0;
- public DownloadThread(int startPos, int currentPartSize,
- RandomAccessFile currentPart) {
- this.startPos = startPos;
- this.currentPartSize = currentPartSize;
- this.currentPart = currentPart;
- }
- public void run() {
- try {
- URL url = new URL(path);
- HttpURLConnection conn = (HttpURLConnection) url
- .openConnection();
- conn.setConnectTimeout(5 * 1000);
- conn.setRequestMethod("GET");
- conn.setRequestProperty(
- "Accept",
- "image/gif,image/jpeg,image/pjpeg,application/x-shockwaveflash,application/x-ms-xbap,application/xaml+xml,application/vnd.ms-xpsdocument,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 is = conn.getInputStream();
- // 跳过startPos个字符,表明该线程只下载自己负责那部分文件
- is.skip(startPos);
- byte[] by = new byte[1024];
- int hasRead = 0;
- // 读取网络数据,并写入本地文件
- while (length < currentPartSize
- && (hasRead = is.read(by)) != -1) {
- currentPart.write(by, 0, hasRead);
- // 累计该线程下载的总大小
- length += hasRead;
- }
- currentPart.close();
- is.close();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- }
Activity布局XML:
- <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
- android:layout_width="match_parent"
- android:layout_height="match_parent"
- android:orientation="vertical" >
- <LinearLayout
- android:layout_width="match_parent"
- android:layout_height="wrap_content"
- android:orientation="horizontal" >
- <TextView
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:text="输入url:" />
- <EditText
- android:id="@+id/main_et_url"
- android:layout_width="match_parent"
- android:layout_height="wrap_content" />
- </LinearLayout>
- <LinearLayout
- android:layout_width="match_parent"
- android:layout_height="wrap_content"
- android:orientation="horizontal" >
- <TextView
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:text="输入保存的文件名:" />
- <EditText
- android:id="@+id/main_et_name"
- android:layout_width="match_parent"
- android:layout_height="wrap_content" />
- </LinearLayout>
- <Button
- android:id="@+id/main_btn_download"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:text="下载" />
- <ProgressBar
- android:id="@+id/main_progressBar"
- style="@android:style/Widget.ProgressBar.Horizontal"
- android:layout_width="match_parent"
- android:layout_height="wrap_content" />
- </LinearLayout>
权限:
- <!-- 在SD卡中创建与删除文件权限 -->
- <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
- <!-- 向SD卡写入数据权限 -->
- <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
- <!-- 授权访问网络 -->
- <uses-permission android:name="android.permission.INTERNET"/>
- 上一篇使用URL访问网络资源
- 下一篇简单使用URLConnection、HttpURLConnection和HttpClient访问网络资源
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