Android實現網路多執行緒斷點續傳下載
阿新 • • 發佈：2019-02-15
本示例介紹在Android平臺下通過HTTP協議實現斷點續傳下載。
我們編寫的是Andorid的HTTP協議多執行緒斷點下載應用程式。直接使用單執行緒下載HTTP檔案對我們來說是一件非常簡單的事。那麼，多執行緒斷點需要什麼功能？
1.多執行緒下載，
2.支援斷點。
使用多執行緒的好處：使用多執行緒下載會提升檔案下載的速度。那麼多執行緒下載檔案的過程是：
(1)首先獲得下載檔案的長度，然後設定本地檔案的長度。
HttpURLConnection.getContentLength();//獲取下載檔案的長度
RandomAccessFile file = newRandomAccessFile("QQWubiSetup.exe","rwd");
file.setLength(filesize);//設定本地檔案的長度
(2)根據檔案長度和執行緒數計算每條執行緒下載的資料長度和下載位置。
如：檔案的長度為6M，執行緒數為3，那麼，每條執行緒下載的資料長度為2M，每條執行緒開始下載的位置如下圖所示。
例如10M大小，使用3個執行緒來下載，
執行緒下載的資料長度 (10%3 == 0 ？ 10/3:10/3+1) ,第1，2個執行緒下載長度是4M，第三個執行緒下載長度為2M
下載開始位置：執行緒id*每條執行緒下載的資料長度 = ?
下載結束位置：（執行緒id+1）*每條執行緒下載的資料長度-1=?
(3)使用Http的Range頭欄位指定每條執行緒從檔案的什麼位置開始下載，下載到什麼位置為止，
如：指定從檔案的2M位置開始下載，下載到位置(4M-1byte)為止
程式碼如下：HttpURLConnection.setRequestProperty("Range","bytes=2097152-4194303");
(4)儲存檔案，使用RandomAccessFile類指定每條執行緒從本地檔案的什麼位置開始寫入資料。
RandomAccessFile threadfile =new RandomAccessFile("QQWubiSetup.exe ","rwd");
threadfile.seek(2097152);//從檔案的什麼位置開始寫入資料
程式結構如下圖所示：
string.xml檔案中程式碼：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">Hello World, MainActivity!</string>
<string name="app_name">Android網路多執行緒斷點下載</string>
<string name="path">下載路徑</string>
<string name="downloadbutton">下載</string>
<string name="sdcarderror">SDCard不存在或者防寫</string>
<string name="success">下載完成</string>
<string name="error">下載失敗</string>
</resources><?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">
<!-- 下載路徑 -->
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/path"/>
<EditText
android:id="@+id/path"
android:text="http://www.winrar.com.cn/download/wrar380sc.exe"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</EditText>
<!-- 下載按鈕 -->
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/downloadbutton"
android:id="@+id/button"/>
<!-- 進度條 -->
<ProgressBar
android:layout_width="fill_parent"
android:layout_height="20dip"
style="?android:attr/progressBarStyleHorizontal"
android:id="@+id/downloadbar" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:id="@+id/resultView" />
</LinearLayout><?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.android.downloader" android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".MainActivity"
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>
<!-- 在SDCard中建立與刪除檔案許可權 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<!-- 往SDCard寫入資料許可權 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<!-- 訪問internet許可權 -->
<uses-permission android:name="android.permission.INTERNET"/>
</manifest> package com.android.downloader;
import java.io.File;
import com.android.network.DownloadProgressListener;
import com.android.network.FileDownloader;
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.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
private EditText downloadpathText;
private TextView resultView;
private ProgressBar progressBar;
/**
* 當Handler被建立會關聯到建立它的當前執行緒的訊息佇列，該類用於往訊息佇列傳送訊息
* 訊息佇列中的訊息由當前執行緒內部進行處理
*/
private Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case 1:
progressBar.setProgress(msg.getData().getInt("size"));
float num = (float)progressBar.getProgress()/(float)progressBar.getMax();
int result = (int)(num*100);
resultView.setText(result+ "%");
if(progressBar.getProgress()==progressBar.getMax()){
Toast.makeText(MainActivity.this, R.string.success, 1).show();
}
break;
case -1:
Toast.makeText(MainActivity.this, R.string.error, 1).show();
break;
}
}
};
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downloadpathText = (EditText) this.findViewById(R.id.path);
progressBar = (ProgressBar) this.findViewById(R.id.downloadbar);
resultView = (TextView) this.findViewById(R.id.resultView);
Button button = (Button) this.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String path = downloadpathText.getText().toString();
System.out.println(Environment.getExternalStorageState()+"------"+Environment.MEDIA_MOUNTED);
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
download(path, Environment.getExternalStorageDirectory());
}else{
Toast.makeText(MainActivity.this, R.string.sdcarderror, 1).show();
}
}
});
}
/**
* 主執行緒(UI執行緒)
* 對於顯示控制元件的介面更新只是由UI執行緒負責，如果是在非UI執行緒更新控制元件的屬性值，更新後的顯示介面不會反映到螢幕上
* @param path
* @param savedir
*/
private void download(final String path, final File savedir) {
new Thread(new Runnable() {
@Override
public void run() {
FileDownloader loader = new FileDownloader(MainActivity.this, path, savedir, 3);
progressBar.setMax(loader.getFileSize());//設定進度條的最大刻度為檔案的長度
try {
loader.download(new DownloadProgressListener() {
@Override
public void onDownloadSize(int size) {//實時獲知檔案已經下載的資料長度
Message msg = new Message();
msg.what = 1;
msg.getData().putInt("size", size);
handler.sendMessage(msg);//傳送訊息
}
});
} catch (Exception e) {
handler.obtainMessage(-1).sendToTarget();
}
}
}).start();
}
}package com.android.service;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBOpenHelper extends SQLiteOpenHelper {
private static final String DBNAME = "down.db";
private static final int VERSION = 1;
public DBOpenHelper(Context context) {
super(context, DBNAME, null, VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS filedownlog (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, downlength INTEGER)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS filedownlog");
onCreate(db);
}
} FileService中程式碼：
package com.android.service;
import java.util.HashMap;
import java.util.Map;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
public class FileService {
private DBOpenHelper openHelper;
public FileService(Context context) {
openHelper = new DBOpenHelper(context);
}
/**
* 獲取每條執行緒已經下載的檔案長度
* @param path
* @return
*/
public Map<Integer, Integer> getData(String path){
SQLiteDatabase db = openHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select threadid, downlength from filedownlog where downpath=?", new String[]{path});
Map<Integer, Integer> data = new HashMap<Integer, Integer>();
while(cursor.moveToNext()){
data.put(cursor.getInt(0), cursor.getInt(1));
}
cursor.close();
db.close();
return data;
}
/**
* 儲存每條執行緒已經下載的檔案長度
* @param path
* @param map
*/
public void save(String path, Map<Integer, Integer> map){//int threadid, int position
SQLiteDatabase db = openHelper.getWritableDatabase();
db.beginTransaction();
try{
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
db.execSQL("insert into filedownlog(downpath, threadid, downlength) values(?,?,?)",
new Object[]{path, entry.getKey(), entry.getValue()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}
/**
* 實時更新每條執行緒已經下載的檔案長度
* @param path
* @param map
*/
public void update(String path, Map<Integer, Integer> map){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.beginTransaction();
try{
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
db.execSQL("update filedownlog set downlength=? where downpath=? and threadid=?",
new Object[]{entry.getValue(), path, entry.getKey()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}
/**
* 當檔案下載完成後，刪除對應的下載記錄
* @param path
*/
public void delete(String path){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.execSQL("delete from filedownlog where downpath=?", new Object[]{path});
db.close();
}
}package com.android.network;
public interface DownloadProgressListener {
public void onDownloadSize(int size);
} package com.android.network;
import java.io.File;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import com.android.service.FileService;
import android.content.Context;
import android.util.Log;
public class FileDownloader {
private static final String TAG = "FileDownloader";
private Context context;
private FileService fileService;
/* 已下載檔案長度 */
private int downloadSize = 0;
/* 原始檔案長度 */
private int fileSize = 0;
/* 執行緒數 */
private DownloadThread[] threads;
/* 本地儲存檔案 */
private File saveFile;
/* 快取各執行緒下載的長度*/
private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>();
/* 每條執行緒下載的長度 */
private int block;
/* 下載路徑 */
private String downloadUrl;
/**
* 獲取執行緒數
*/
public int getThreadSize() {
return threads.length;
}
/**
* 獲取檔案大小
* @return
*/
public int getFileSize() {
return fileSize;
}
/**
* 累計已下載大小
* @param size
*/
protected synchronized void append(int size) {
downloadSize += size;
}
/**
* 更新指定執行緒最後下載的位置
* @param threadId 執行緒id
* @param pos 最後下載的位置
*/
protected synchronized void update(int threadId, int pos) {
this.data.put(threadId, pos);
this.fileService.update(this.downloadUrl, this.data);
}
/**
* 構建檔案下載器
* @param downloadUrl 下載路徑
* @param fileSaveDir 檔案儲存目錄
* @param threadNum 下載執行緒數
*/
public FileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) {
try {
this.context = context;
this.downloadUrl = downloadUrl;
fileService = new FileService(this.context);
URL url = new URL(this.downloadUrl);
if(!fileSaveDir.exists()) fileSaveDir.mkdirs();
this.threads = new DownloadThread[threadNum];
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(5*1000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Referer", downloadUrl);
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; 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");
conn.connect();
printResponseHeader(conn);
if (conn.getResponseCode()==200) {
this.fileSize = conn.getContentLength();//根據響應獲取檔案大小
if (this.fileSize <= 0) throw new RuntimeException("Unkown file size ");
String filename = getFileName(conn);//獲取檔名稱
this.saveFile = new File(fileSaveDir, filename);//構建儲存檔案
Map<Integer, Integer> logdata = fileService.getData(downloadUrl);//獲取下載記錄
if(logdata.size()>0){//如果存在下載記錄
for(Map.Entry<Integer, Integer> entry : logdata.entrySet())
data.put(entry.getKey(), entry.getValue());//把各條執行緒已經下載的資料長度放入data中
}
if(this.data.size()==this.threads.length){//下面計算所有執行緒已經下載的資料長度
for (int i = 0; i < this.threads.length; i++) {
this.downloadSize += this.data.get(i+1);
}
print("已經下載的長度"+ this.downloadSize);
}
//計算每條執行緒下載的資料長度
this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
}else{
throw new RuntimeException("server no response ");
}
} catch (Exception e) {
print(e.toString());
throw new RuntimeException("don't connection this url");
}
}
/**
* 獲取檔名
* @param conn
* @return
*/
private String getFileName(HttpURLConnection conn) {
String filename = this.downloadUrl.substring(this.downloadUrl.lastIndexOf('/') + 1);
if(filename==null || "".equals(filename.trim())){//如果獲取不到檔名稱
for (int i = 0;; i++) {
String mine = conn.getHeaderField(i);
if (mine == null) break;
if("content-disposition".equals(conn.getHeaderFieldKey(i).toLowerCase())){
Matcher m = Pattern.compile(".*filename=(.*)").matcher(mine.toLowerCase());
if(m.find()) return m.group(1);
}
}
filename = UUID.randomUUID()+ ".tmp";//預設取一個檔名
}
return filename;
}
/**
* 開始下載檔案
* @param listener 監聽下載數量的變化,如果不需要了解實時下載的數量,可以設定為null
* @return 已下載檔案大小
* @throws Exception
*/
public int download(DownloadProgressListener listener) throws Exception{
try {
RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
if(this.fileSize>0) randOut.setLength(this.fileSize);
randOut.close();
URL url = new URL(this.downloadUrl);
if(this.data.size() != this.threads.length){
this.data.clear();
for (int i = 0; i < this.threads.length; i++) {
this.data.put(i+1, 0);//初始化每條執行緒已經下載的資料長度為0
}
}
for (int i = 0; i < this.threads.length; i++) {//開啟執行緒進行下載
int downLength = this.data.get(i+1);
if(downLength < this.block && this.downloadSize<this.fileSize){//判斷執行緒是否已經完成下載,否則繼續下載
this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
this.threads[i].setPriority(7);
this.threads[i].start();
}else{
this.threads[i] = null;
}
}
this.fileService.save(this.downloadUrl, this.data);
boolean notFinish = true;//下載未完成
while (notFinish) {// 迴圈判斷所有執行緒是否完成下載
Thread.sleep(900);
notFinish = false;//假定全部執行緒下載完成
for (int i = 0; i < this.threads.length; i++){
if (this.threads[i] != null && !this.threads[i].isFinish()) {//如果發現執行緒未完成下載
notFinish = true;//設定標誌為下載沒有完成
if(this.threads[i].getDownLength() == -1){//如果下載失敗,再重新下載
this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
this.threads[i].setPriority(7);
this.threads[i].start();
}
}
}
if(listener!=null) listener.onDownloadSize(this.downloadSize);//通知目前已經下載完成的資料長度
}
fileService.delete(this.downloadUrl);
} catch (Exception e) {
print(e.toString());
throw new Exception("file download fail");
}
return this.downloadSize;
}
/**
* 獲取Http響應頭欄位
* @param http
* @return
*/
public static Map<String, String> getHttpResponseHeader(HttpURLConnection http) {
Map<String, String> header = new LinkedHashMap<String, String>();
for (int i = 0;; i++) {
String mine = http.getHeaderField(i);
if (mine == null) break;
header.put(http.getHeaderFieldKey(i), mine);
}
return header;
}
/**
* 列印Http頭欄位
* @param http
*/
public static void printResponseHeader(HttpURLConnection http){
Map<String, String> header = getHttpResponseHeader(http);
for(Map.Entry<String, String> entry : header.entrySet()){
String key = entry.getKey()!=null ? entry.getKey()+ ":" : "";
print(key+ entry.getValue());
}
}
private static void print(String msg){
Log.i(TAG, msg);
}
}package com.android.network;
import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import android.util.Log;
public class DownloadThread extends Thread {
private static final String TAG = "DownloadThread";
private File saveFile;
private URL downUrl;
private int block;
/* 下載開始位置 */
private int threadId = -1;
private int downLength;
private boolean finish = false;
private FileDownloader downloader;
public DownloadThread(FileDownloader downloader, URL downUrl, File saveFile, int block, int downLength, int threadId) {
this.downUrl = downUrl;
this.saveFile = saveFile;
this.block = block;
this.downloader = downloader;
this.threadId = threadId;
this.downLength = downLength;
}
@Override
public void run() {
if(downLength < block){//未下載完成
try {
HttpURLConnection http = (HttpURLConnection) downUrl.openConnection();
http.setConnectTimeout(5 * 1000);
http.setRequestMethod("GET");
http.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
http.setRequestProperty("Accept-Language", "zh-CN");
http.setRequestProperty("Referer", downUrl.toString());
http.setRequestProperty("Charset", "UTF-8");
int startPos = block * (threadId - 1) + downLength;//開始位置
int endPos = block * threadId -1;//結束位置
http.setRequestProperty("Range", "bytes=" + startPos + "-"+ endPos);//設定獲取實體資料的範圍
http.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; 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)");
http.setRequestProperty("Connection", "Keep-Alive");
InputStream inStream = http.getInputStream();
byte[] buffer = new byte[1024];
int offset = 0;
print("Thread " + this.threadId + " start download from position "+ startPos);
RandomAccessFile threadfile = new RandomAccessFile(this.saveFile, "rwd");
threadfile.seek(startPos);
while ((offset = inStream.read(buffer, 0, 1024)) != -1) {
threadfile.write(buffer, 0, offset);
downLength += offset;
downloader.update(this.threadId, downLength);
downloader.append(offset);
}
threadfile.close();
inStream.close();
print("Thread " + this.threadId + " download finish");
this.finish = true;
} catch (Exception e) {
this.downLength = -1;
print("Thread "+ this.threadId+ ":"+ e);
}
}
}
private static void print(String msg){
Log.i(TAG, msg);
}
/**
* 下載是否完成
* @return
*/
public boolean isFinish() {
return finish;
}
/**
* 已經下載的內容大小
* @return 如果返回值為-1,代表下載失敗
*/
public long getDownLength() {
return downLength;
}
}