android 多线程断点续传下载 一

想做一个下载功能，当然理想的功能要支持多任务同时下载，断点续传的功能，我想一步一步来，首先困难摆在了多任务这里

开始我的思路是在一个Service中启动下载的流操作，然后通过Service中声明一个Activity中的Handler更新UI(比如进度条。。。)

可是我发现在Service中声明一个Activity中的Handler是做不到的（可能只是我做不到吧，无法申请内存）

于是，我决定在Activity中直接启动线程，让其运行，调用自身的Handler来更新UI，没想到在这个下载Activity onPause（）的时候，线程还是活的，也就是说可以继续下载，下例是我做的一个两个任务同时下载的小例子，后面会把理想中的功能都陆续添加上的...

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical" android:layout_width="fill_parent"android:layout_height="fill_parent"><ProgressBar style="?android:attr/progressBarStyleHorizontal"android:layout_height="wrap_content" android:id="@+id/progressBar1"android:layout_width="fill_parent"></ProgressBar><TextView android:layout_width="fill_parent" android:id="@+id/textView1"android:layout_height="wrap_content" /><ProgressBar style="?android:attr/progressBarStyleHorizontal"android:layout_height="wrap_content" android:id="@+id/progressBar2"android:layout_width="fill_parent"></ProgressBar><TextView android:layout_width="fill_parent" android:id="@+id/textView2"android:layout_height="wrap_content" /></LinearLayout>

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="sms.down"      android:versionCode="1"      android:versionName="1.0">    <uses-sdk android:minSdkVersion="9" />    <application android:icon="@drawable/icon" android:label="@string/app_name">        <activity android:name=".MulThreadDownload"                  android:label="@string/app_name">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application>        <!-- 访问 internet 权限 --><uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.CALL_PHONE" /><uses-permission android:name="android.permission.SEND_SMS" /><uses-permission android:name="android.permission.READ_CONTACTS"/><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /><uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /><uses-permission android:name="android.permission.READ_PHONE_STATE"/></manifest>

package sms.down;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;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.widget.ProgressBar;import android.widget.TextView;public class MulThreadDownload extends Activity {/** Called when the activity is first created. */private ProgressBar pb1 = null;private TextView tv1 = null;private ProgressBar pb2 = null;private TextView tv2 = null;private String root = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator;private String downloadFile = "http://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3";private String downloadFile1 = "http://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3";// 声明已经读过的长度变量private int hasRead = 0;public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);pb1 = (ProgressBar) findViewById(R.id.progressBar1);tv1 = (TextView) findViewById(R.id.textView1);pb2 = (ProgressBar) findViewById(R.id.progressBar2);tv2 = (TextView) findViewById(R.id.textView2);download(downloadFile, root, pb1, tv1);download(downloadFile1, root, pb2, tv2);}private void download(String url, String targetPath, ProgressBar pb,TextView tv) {DownloadThread dt = new DownloadThread(url, targetPath, pb, tv);dt.start();}// 自定义一个Handler类，处理线程消息public class MyHandler extends Handler {private ProgressBar progressBar;private TextView textView;// 通过构造函数来确定给哪个ProgressBar刷新public MyHandler(ProgressBar progressBar, TextView textView) {this.progressBar = progressBar;this.textView = textView;}public void handleMessage(Message msg) {this.progressBar.setProgress(msg.arg1);this.textView.setText(msg.arg1 + "%");super.handleMessage(msg);}}// 下载线程public class DownloadThread extends Thread {private String url = "";private String targetPath = "";private int hasDownload = 0;private int len = -1;private byte buffer[] = new byte[4 * 1024];private int size = 0;private int rate = 0;private MyHandler myHandler = null;private Message msg = null;private ProgressBar pb = null;private TextView tv = null;public DownloadThread(String url, String targetPath, ProgressBar pb,TextView tv) {this.url = url;this.targetPath = targetPath;this.pb = pb;this.tv = tv;myHandler = new MyHandler(this.pb, this.tv);}public void run() {String targetFileName = this.targetPath+ this.url.substring(this.url.lastIndexOf("/") + 1,this.url.length());File downloadFile = new File(targetFileName);if (!downloadFile.exists()) {try {downloadFile.createNewFile();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}try {URL fileUrl = new URL(this.url);HttpURLConnection conn = (HttpURLConnection) fileUrl.openConnection();// 获取文件大小size = conn.getContentLength();InputStream is = conn.getInputStream();OutputStream os = new FileOutputStream(targetFileName);while ((len = is.read(buffer)) != -1) {os.write(buffer);hasDownload += len;rate = (hasDownload * 100 / size);msg = new Message();msg.arg1 = rate;myHandler.sendMessage(msg);System.out.println(rate + "%");}} catch (MalformedURLException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {e.printStackTrace();}}}}

源码下载