android多线程下载2

在上一集中,我们简单介绍了如何创建多任务下载,但那种还不能拿来实用,这一集我们重点通过代码为大家展示如何创建多线程断点续传下载,这在实际项目中很常用.

main.xml:

<?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" 
 > 
 <EditText 
 android:layout_width="match_parent" 
 android:layout_height="wrap_content" 
 android:id="@+id/editText" 
 android:text="http://gongxue.cn/yingyinkuaiche/UploadFiles_9323/201008/2010082909434077.mp3" 
 /> 
 <LinearLayout 
 android:orientation="horizontal" 
 android:layout_width="match_parent" 
 android:layout_height="wrap_content" 
 > 
 <Button 
 android:layout_width="wrap_content" 
 android:layout_height="wrap_content" 
 android:id="@+id/downButton" 
 android:text="Download" 
 /> 
 <Button 
 android:layout_width="wrap_content" 
 android:layout_height="wrap_content" 
 android:id="@+id/pauseButton" 
 android:enabled="false" 
 android:text="Pause" 
 /> 
 </LinearLayout> 
 
 <ProgressBar 
 android:layout_width="match_parent" 
 android:layout_height="18dp" 
 style="?android:attr/progressBarStyleHorizontal" 
 android:id="@+id/progressBar" 
 /> 
 <TextView 
 android:layout_width="fill_parent" 
 android:layout_height="wrap_content" 
 android:id="@+id/textView" 
 android:gravity="center" 
 /> 
</LinearLayout> 

String.xml:

<?xml version="1.0" encoding="utf-8"?> 
<resources> 
 <string name="hello">Hello World, Main!</string> 
 <string name="app_name">多线程断点续传下载</string> 
</resources> 

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
 package="sms.multithreaddownload" 
 android:versionCode="1" 
 android:versionName="1.0"> 
 <application android:icon="@drawable/icon" android:label="@string/app_name"> 
 <activity android:name=".Main" 
 android:label="@string/app_name"> 
 <intent-filter> 
 <action android:name="android.intent.action.MAIN" /> 
 <category android:name="android.intent.category.LAUNCHER" /> 
 </intent-filter> 
 </activity> 
 <uses-library android:name="android.test.runner" /> 
 </application> 
 <uses-sdk android:minSdkVersion="8" /> 
 <instrumentation 
 android:targetPackage="sms.multithreaddownload" 
 android:name="android.test.InstrumentationTestRunner" /> 
 <!-- 访问网络的权限 --> 
 <uses-permission android:name="android.permission.INTERNET"/> 
 <!-- SDCard写数据的权限 --> 
 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> 
 
 
</manifest> 

activity程序:

package sms.multithreaddownload;  
 
import java.io.File;  
 
import sms.multithreaddownload.bean.DownloadListener;  
import sms.multithreaddownload.service.DownloadService;  
import android.app.Activity;  
import android.os.Bundle;  
import android.os.Environment;  
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 android.widget.TextView;  
import android.widget.Toast;  
 
public class Main extends Activity {  
 private EditText path;  
 private TextView progress;  
 private ProgressBar progressBar;  
 private Handler handler = new UIHandler();  
 private DownloadService servcie;  
 private Button downButton;  
 private Button pauseButton;  
 
 private final class UIHandler extends Handler {  
 @Override 
 public void handleMessage(Message msg) {  
 switch (msg.what) {  
 case 1:  
 int downloaded_size = msg.getData().getInt("size");  
                    progressBar.setProgress(downloaded_size);  
 int result = (int) ((float) downloaded_size / progressBar.getMax() * 100);  
                    progress.setText(result + "%");  
 if (progressBar.getMax() == progressBar.getProgress()) {  
                        Toast.makeText(getApplicationContext(), "下载完成", Toast.LENGTH_LONG).show();  
                    }  
            }  
        }  
    }  
 
 @Override 
 public void onCreate(Bundle savedInstanceState) {  
 super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
        path = (EditText) this.findViewById(R.id.editText);  
        progress = (TextView) this.findViewById(R.id.textView);  
        progressBar = (ProgressBar) this.findViewById(R.id.progressBar);  
        downButton = (Button) this.findViewById(R.id.downButton);  
        pauseButton = (Button) this.findViewById(R.id.pauseButton);  
        downButton.setOnClickListener(new DownloadButton());  
        pauseButton.setOnClickListener(new PauseButton());  
    }  
 
 private final class DownloadButton implements View.OnClickListener {  
 @Override 
 public void onClick(View v) {  
            DownloadTask task;  
 try {  
                task = new DownloadTask(path.getText().toString());  
                servcie.isPause = false;  
                v.setEnabled(false);  
                pauseButton.setEnabled(true);  
 new Thread(task).start();  
            } catch (Exception e) {  
                e.printStackTrace();  
            }  
        }  
    }  
 
 public class PauseButton implements OnClickListener {  
 @Override 
 public void onClick(View v) {  
            servcie.isPause = true;  
            v.setEnabled(false);  
            downButton.setEnabled(true);  
        }  
    }  
 
 public void pause(View v) {  
    }  
 
 private final class DownloadTask implements Runnable {  
 
 public DownloadTask(String target) throws Exception {  
 if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {  
                File destination = Environment.getExternalStorageDirectory();  
                servcie = new DownloadService(target, destination, 3, getApplicationContext());  
                progressBar.setMax(servcie.fileSize);  
            } else {  
                Toast.makeText(getApplicationContext(), "SD卡不存在或写保护!", Toast.LENGTH_LONG).show();  
            }  
        }  
 
 @Override 
 public void run() {  
 try {  
                servcie.download(new DownloadListener() {  
 
 @Override 
 public void onDownload(int downloaded_size) {  
                        Message message = new Message();  
                        message.what = 1;  
                        message.getData().putInt("size", downloaded_size);  
                        handler.sendMessage(message);  
                    }  
 
                });  
            } catch (Exception e) {  
                e.printStackTrace();  
            }  
 
        }  
    }  
}  

工具类:

package sms.multithreaddownload.bean;  
 
import android.content.Context;  
import android.database.sqlite.SQLiteDatabase;  
import android.database.sqlite.SQLiteOpenHelper;  
 
public class DBHelper extends SQLiteOpenHelper {  
 
 public DBHelper(Context context) {  
 super(context, "MultiDownLoad.db", null, 1);  
    }  
 
 @Override 
 public void onCreate(SQLiteDatabase db) {  
        db.execSQL("CREATE TABLE fileDownloading(_id integer primary key autoincrement,downPath varchar(100),threadId INTEGER,downLength INTEGER)");  
    }  
 
 @Override 
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  
 // TODO Auto-generated method stub 
 
    }  
 
}  

package sms.multithreaddownload.bean;  
 
public interface DownloadListener {  
 public void onDownload(int downloaded_size);  
}  

package sms.multithreaddownload.bean;  
 
import java.io.File;  
import java.io.InputStream;  
import java.io.RandomAccessFile;  
import java.net.HttpURLConnection;  
import java.net.URL;  
 
import sms.multithreaddownload.service.DownloadService;  
 
import android.util.Log;  
 
public final class MultiThreadDownload implements Runnable {  
 public int id;  
 private RandomAccessFile savedFile;  
 private String path;  
 /* 当前已下载量 */ 
 public int currentDownloadSize = 0;  
 /* 下载状态 */ 
 public boolean finished;  
 /* 用于监视下载状态 */ 
 private final DownloadService downloadService;  
 /* 线程下载任务的起始点 */ 
 public int start;  
 /* 线程下载任务的结束点 */ 
 private int end;  
 
 public MultiThreadDownload(int id, File savedFile, int block, String path, Integer downlength, DownloadService downloadService) throws Exception {  
 this.id = id;  
 this.path = path;  
 if (downlength != null) this.currentDownloadSize = downlength;  
 this.savedFile = new RandomAccessFile(savedFile, "rwd");  
 this.downloadService = downloadService;  
        start = id * block + currentDownloadSize;  
        end = (id + 1) * block;  
    }  
 
 @Override 
 public void run() {  
 try {  
            HttpURLConnection conn = (HttpURLConnection) new URL(path).openConnection();  
            conn.setConnectTimeout(5000);  
            conn.setRequestMethod("GET");  
            conn.setRequestProperty("Range", "bytes=" + start + "-" + end); // 设置获取数据的范围 
 
            InputStream in = conn.getInputStream();  
 byte[] buffer = new byte[1024];  
 int len = 0;  
            savedFile.seek(start);  
 while (!downloadService.isPause && (len = in.read(buffer)) != -1) {  
                savedFile.write(buffer, 0, len);  
                currentDownloadSize += len;  
            }  
            savedFile.close();  
            in.close();  
            conn.disconnect();  
 if (!downloadService.isPause) Log.i(DownloadService.TAG, "Thread " + (this.id + 1) + "finished");  
            finished = true;  
        } catch (Exception e) {  
            e.printStackTrace();  
 throw new RuntimeException("File downloading error!");  
        }  
    }  
}  

 service类:

package sms.multithreaddownload.service;  
 
import java.io.File;  
import java.io.RandomAccessFile;  
import java.net.HttpURLConnection;  
import java.net.URL;  
import java.util.HashMap;  
import java.util.List;  
import java.util.Map;  
import java.util.Map.Entry;  
import java.util.UUID;  
import java.util.concurrent.ConcurrentHashMap;  
import java.util.regex.Matcher;  
import java.util.regex.Pattern;  
 
import sms.multithreaddownload.bean.DBHelper;  
import sms.multithreaddownload.bean.DownloadListener;  
import sms.multithreaddownload.bean.MultiThreadDownload;  
 
import android.content.Context;  
import android.database.Cursor;  
import android.database.sqlite.SQLiteDatabase;  
 
 
public class DownloadService {  
 public static final String TAG = "tag";  
 /* 用于查询数据库 */ 
 private DBHelper dbHelper;  
 /* 要下载的文件大小 */ 
 public int fileSize;  
 /* 每条线程需要下载的数据量 */ 
 private int block;  
 /* 保存文件地目录 */ 
 private File savedFile;  
 /* 下载地址 */ 
 private String path;  
 /* 是否停止下载 */ 
 public boolean isPause;  
 /* 线程数 */ 
 private MultiThreadDownload[] threads;  
 /* 各线程已经下载的数据量 */ 
 private Map<Integer, Integer> downloadedLength = new ConcurrentHashMap<Integer, Integer>();  
 
 public DownloadService(String target, File destination, int thread_size, Context context) throws Exception {  
        dbHelper = new DBHelper(context);  
 this.threads = new MultiThreadDownload[thread_size];  
 this.path = target;  
        URL url = new URL(target);  
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();  
        conn.setConnectTimeout(5000);  
        conn.setRequestMethod("GET");  
 
 if (conn.getResponseCode() != 200) {  
 throw new RuntimeException("server no response!");  
        }  
 
        fileSize = conn.getContentLength();  
 if (fileSize <= 0) {  
 throw new RuntimeException("file is incorrect!");  
        }  
        String fileName = getFileName(conn);  
 if (!destination.exists()) destination.mkdirs();  
 // 构建一个同样大小的文件 
 this.savedFile = new File(destination, fileName);  
        RandomAccessFile doOut = new RandomAccessFile(savedFile, "rwd");  
        doOut.setLength(fileSize);  
        doOut.close();  
        conn.disconnect();  
 
 // 计算每条线程需要下载的数据长度 
 this.block = fileSize % thread_size == 0 ? fileSize / thread_size : fileSize / thread_size + 1;  
 // 查询已经下载的记录 
        downloadedLength = this.getDownloadedLength(path);  
    }  
 
 private Map<Integer, Integer> getDownloadedLength(String path) {  
        SQLiteDatabase db = dbHelper.getReadableDatabase();  
        String sql = "SELECT threadId,downLength FROM fileDownloading WHERE downPath=?";  
        Cursor cursor = db.rawQuery(sql, new String[] { path });  
        Map<Integer, Integer> data = new HashMap<Integer, Integer>();  
 while (cursor.moveToNext()) {  
            data.put(cursor.getInt(0), cursor.getInt(1));  
        }  
        db.close();  
 return data;  
    }  
 
 private String getFileName(HttpURLConnection conn) {  
        String fileName = path.substring(path.lastIndexOf("/") + 1, path.length());  
 if (fileName == null || "".equals(fileName.trim())) {  
            String content_disposition = null;  
 for (Entry<String, List<String>> entry : conn.getHeaderFields().entrySet()) {  
 if ("content-disposition".equalsIgnoreCase(entry.getKey())) {  
                    content_disposition = entry.getValue().toString();  
                }  
            }  
 try {  
                Matcher matcher = Pattern.compile(".*filename=(.*)").matcher(content_disposition);  
 if (matcher.find()) fileName = matcher.group(1);  
            } catch (Exception e) {  
                fileName = UUID.randomUUID().toString() + ".tmp"; // 默认名 
            }  
        }  
 return fileName;  
    }  
 
 public void download(DownloadListener listener) throws Exception {  
 this.deleteDownloading(); // 先删除上次的记录,再重新添加 
 for (int i = 0; i < threads.length; i++) {  
            threads[i] = new MultiThreadDownload(i, savedFile, block, path, downloadedLength.get(i), this);  
 new Thread(threads[i]).start();  
        }  
 this.saveDownloading(threads);  
 
 while (!isFinish(threads)) {  
            Thread.sleep(900);  
 if (listener != null) listener.onDownload(getDownloadedSize(threads));  
 this.updateDownloading(threads);  
        }  
 if (!this.isPause) this.deleteDownloading();// 完成下载之后删除本次下载记录 
    }  
 
 private void saveDownloading(MultiThreadDownload[] threads) {  
        SQLiteDatabase db = dbHelper.getWritableDatabase();  
 try {  
            db.beginTransaction();  
 for (MultiThreadDownload thread : threads) {  
                String sql = "INSERT INTO fileDownloading(downPath,threadId,downLength) values(?,?,?)";  
                db.execSQL(sql, new Object[] { path, thread.id, 0 });  
            }  
            db.setTransactionSuccessful();  
        } finally {  
            db.endTransaction();  
            db.close();  
        }  
    }  
 
 private void deleteDownloading() {  
        SQLiteDatabase db = dbHelper.getWritableDatabase();  
        String sql = "DELETE FROM fileDownloading WHERE downPath=?";  
        db.execSQL(sql, new Object[] { path });  
        db.close();  
    }  
 
 private void updateDownloading(MultiThreadDownload[] threads) {  
        SQLiteDatabase db = dbHelper.getWritableDatabase();  
 try {  
            db.beginTransaction();  
 for (MultiThreadDownload thread : threads) {  
                String sql = "UPDATE fileDownloading SET downLength=? WHERE threadId=? AND downPath=?";  
                db.execSQL(sql, new String[] { thread.currentDownloadSize + "", thread.id + "", path });  
            }  
            db.setTransactionSuccessful();  
        } finally {  
            db.endTransaction();  
            db.close();  
        }  
    }  
 
 private int getDownloadedSize(MultiThreadDownload[] threads) {  
 int sum = 0;  
 for (int len = threads.length, i = 0; i < len; i++) {  
            sum += threads[i].currentDownloadSize;  
        }  
 return sum;  
    }  
 
 private boolean isFinish(MultiThreadDownload[] threads) {  
 try {  
 for (int len = threads.length, i = 0; i < len; i++) {  
 if (!threads[i].finished) {  
 return false;  
                }  
            }  
 return true;  
        } catch (Exception e) {  
 return false;  
        }  
    }  
}  

运行效果:

源码下载地址