android多线程断点下载

package com.itheima.multidownloader;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.InputStream;import java.io.InputStreamReader;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.view.View;import android.widget.EditText;import android.widget.LinearLayout;import android.widget.ProgressBar;public class MainActivity extends Activity {private EditText et_path;private EditText et_thread_count;private String path;// 总的线程的个数private int totalThreadCount;/** * 正在运行的线程的数量 */private int runningThreadCount;private LinearLayout ll_container;private List<ProgressBar> pbs;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);et_path = (EditText) findViewById(R.id.et_path);et_thread_count = (EditText) findViewById(R.id.et_threadcount);ll_container = (LinearLayout) findViewById(R.id.ll_container);}public void download(View view) {path = et_path.getText().toString().trim();String str_count = et_thread_count.getText().toString().trim();totalThreadCount = Integer.parseInt(str_count);ll_container.removeAllViews();//删除旧的pbs = new ArrayList<ProgressBar>();for(int i= 0;i<totalThreadCount;i++){//有几个线程 就创建几个进度条ProgressBar pb = (ProgressBar) View.inflate(this, R.layout.pb, null);ll_container.addView(pb);pbs.add(pb);}new Thread() {public void run() {try {// 推荐大家使用exe文件作为下载测试的文件URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");int code = conn.getResponseCode();if (code == 200) {int length = conn.getContentLength();System.out.println("服务器文件的长度为:" + length);RandomAccessFile raf = new RandomAccessFile(Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+getDownLoadFileName(path), "rw");// 在本地创建一个空文件大小和服务器的文件大小保持一致raf.setLength(length);raf.close();int blocksize = length / totalThreadCount;// 把服务器的资源等分成3份// 每一份的大小System.out.println("每一份:" + blocksize);runningThreadCount = totalThreadCount;for (int threadid = 0; threadid < totalThreadCount; threadid++) {int startPosition = threadid * blocksize;int endPosition = (threadid + 1) * blocksize - 1;if (threadid == (totalThreadCount - 1)) {endPosition = length - 1;}System.out.println("线程理论:" + threadid + "下载的范围:"+ startPosition + "~~" + endPosition);// 开启子线程,让每个子线程下载对应位置的数据..new DownloadThread(threadid, startPosition, endPosition).start();}}} catch (Exception e) {e.printStackTrace();}};}.start();}public class DownloadThread extends Thread {/** * 线程id */private int threadid;/** * 当前线程下载的开始位置 */private int startPosition;/** * 当前线程下载的结束位置 */private int endPosition;/** * 当前线程下载的进度的总大小 */private int threadTotal;/** * 上一次下载的总大小 */private int lastdownloadTotalSize;public DownloadThread(int threadid, int startPosition, int endPosition) {this.threadid = threadid;this.startPosition = startPosition;this.endPosition = endPosition;threadTotal = endPosition - startPosition;pbs.get(threadid).setMax(threadTotal);//设置当前线程的进度条的总大小}@Overridepublic void run() {System.out.println("线程:" + threadid + "开始工作了");// 让当前线程下载自己对应范围的数据try {// 判断是否已经下载过一部分的数据.File finfo = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+totalThreadCount+ getDownLoadFileName(path) + threadid + ".txt");if (finfo.exists() && finfo.length() > 0) {FileInputStream fis = new FileInputStream(finfo);BufferedReader br = new BufferedReader(new InputStreamReader(fis));String lastposition = br.readLine();// 这个线程上一次下载的大小int intlastposition = Integer.parseInt(lastposition);lastdownloadTotalSize = intlastposition - startPosition;startPosition = intlastposition;fis.close();}URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");System.out.println("线程真实下载开始和结束:" + threadid + "下载的范围:"+ startPosition + "~~" + endPosition);conn.setRequestProperty("Range", "bytes=" + startPosition + "-"+ endPosition);// 从服务器下载资源.int code = conn.getResponseCode(); // 206 请求部分数据成功if (code == 206) {InputStream is = conn.getInputStream();RandomAccessFile raf = new RandomAccessFile(Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+getDownLoadFileName(path), "rw");// ★ 非常重要指定文件写的开始位置raf.seek(startPosition);byte[] buffer = new byte[1024];int len = -1;int total = 0;// 当前线程这一次下载了多少的数据while ((len = is.read(buffer)) != -1) {raf.write(buffer, 0, len);// 把当前下载的位置记录下来.total += len;RandomAccessFile inforaf = new RandomAccessFile(Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+totalThreadCount + getDownLoadFileName(path)+ threadid + ".txt", "rwd");// 每一次更新// 数据都被同步到底层硬盘// 存当前线程已经下载到了哪个位置inforaf.write(String.valueOf(startPosition + total).getBytes());inforaf.close();pbs.get(threadid).setProgress(total+lastdownloadTotalSize);}is.close();raf.close();System.out.println("线程:" + threadid + "下载完毕了...");}} catch (Exception e) {e.printStackTrace();} finally {synchronized (MainActivity.this) {runningThreadCount--;if (runningThreadCount <= 0) {System.out.println("多线程下载完毕.");for (int i = 0; i < totalThreadCount; i++) {File f = new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+totalThreadCount+ getDownLoadFileName(path) + i + ".txt");System.out.println(f.delete());}}}}}}/** * 根据路径获取文件名 *  * @param path * @return */public String getDownLoadFileName(String path) {return path.substring(path.lastIndexOf("/") + 1);}}