文章出处
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:
String.xml
Hello World, Main!
多线程断点续传下载
AndroidManifest.xml:
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 downloadedLength = new ConcurrentHashMap();
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 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 data = new HashMap();
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> 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