以下代碼是基於百度雲網盤：http://pan.baidu.com/s/1dD1Xo8T 中的demo進行優化及功能添加。
以下代碼實現功能有：多線程下載、多任務並行下載以及下載進度和下載速度的顯示等功能。
實現思路：根據線程數分割待下載文件；利用HttpURLConnection實現各部分文件的下載；利用RandomAccessFile實現下載內容的保存；各線程下載任務信息保存在數據庫，以便暫停和恢復下載。
demo已上傳到github：https://github.com/shichaohui/FileDownloadDemo.git 歡迎下載。
效果圖：
主要代碼
DownLoadHelper.java:
package com.example.test;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* 利用數據庫來記錄下載信息
*
* @author [email protected]
*/
public class DownLoadHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "download.db";
private static final String TB_NAME = "download_info";
private static final int DOWNLOAD_VERSION = 1;
public DownLoadHelper(Context context) {
super(context, DB_NAME, null, DOWNLOAD_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table "
+ TB_NAME
+ "(_id integer PRIMARY KEY AUTOINCREMENT, thread_id integer, "
+ "start_pos integer, end_pos integer, compelete_size integer,url char)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
這個類沒什麼好說的，就是創建數據庫和數據表。
DownlaodSqlTool.java
package com.example.test;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
/**
* 數據庫操作工具類
*
* @author [email protected]
*/
public class DownlaodSqlTool {
private static DownlaodSqlTool instance = null;
private DownLoadHelper dbHelper = null;
private DownlaodSqlTool(Context context) {
dbHelper = new DownLoadHelper(context);
}
private static synchronized void syncInit(Context context) {
if (instance == null) {
instance = new DownlaodSqlTool(context);
}
}
public static DownlaodSqlTool getInstance(Context context) {
if (instance == null) {
syncInit(context);
}
return instance;
}
/** 將下載的進度等信息保存到數據庫 */
public void insertInfos(List<DownloadInfo> infos) {
SQLiteDatabase database = dbHelper.getWritableDatabase();
for (DownloadInfo info : infos) {
String sql = "insert into download_info(thread_id,start_pos, end_pos,compelete_size,url) values (?,?,?,?,?)";
Object[] bindArgs = { info.getThreadId(), info.getStartPos(),
info.getEndPos(), info.getCompeleteSize(), info.getUrl() };
database.execSQL(sql, bindArgs);
}
}
/** 獲取下載的進度等信息 */
public List<DownloadInfo> getInfos(String urlstr) {
List<DownloadInfo> list = new ArrayList<DownloadInfo>();
SQLiteDatabase database = dbHelper.getWritableDatabase();
String sql = "select thread_id, start_pos, end_pos,compelete_size,url from download_info where url=?";
Cursor cursor = database.rawQuery(sql, new String[] { urlstr });
while (cursor.moveToNext()) {
DownloadInfo info = new DownloadInfo(cursor.getInt(0),
cursor.getInt(1), cursor.getInt(2), cursor.getInt(3),
cursor.getString(4));
list.add(info);
}
cursor.close();
return list;
}
/** 更新數據庫中的下載信息 */
public void updataInfos(int threadId, int compeleteSize, String urlstr) {
SQLiteDatabase database = dbHelper.getWritableDatabase();
String sql = "update download_info set compelete_size=? where thread_id=? and url=?";
Object[] bindArgs = { compeleteSize, threadId, urlstr };
database.execSQL(sql, bindArgs);
}
/** 關閉數據庫 */
public void closeDb() {
dbHelper.close();
}
/** 刪除數據庫中的數據 */
public void delete(String url) {
SQLiteDatabase database = dbHelper.getWritableDatabase();
database.delete("download_info", "url=?", new String[] { url });
}
}單例模式的數據庫操作類，主要實現數據的增刪改查等操作。
DownloadInfo.java
package com.example.test;
/**
* 保存每個下載線程下載信息類
*
* @author [email protected]
*/
public class DownloadInfo {
private int threadId; // 下載線程的id
private int startPos; // 開始點
private int endPos; // 結束點
private int compeleteSize; // 完成度
private String url; // 下載文件的URL地址
/**
*
* @param threadId
* 下載線程的id
* @param startPos
* 開始點
* @param endPos
* 結束點
* @param compeleteSize
* // 已下載的大小
* @param url
* 下載地址
*/
public DownloadInfo(int threadId, int startPos, int endPos,
int compeleteSize, String url) {
this.threadId = threadId;
this.startPos = startPos;
this.endPos = endPos;
this.compeleteSize = compeleteSize;
this.url = url;
}
public DownloadInfo() {
}
/** 獲取下載地址 */
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
/** 獲取下載線程的Id */
public int getThreadId() {
return threadId;
}
public void setThreadId(int threadId) {
this.threadId = threadId;
}
/** 獲取下載的開始位置 */
public int getStartPos() {
return startPos;
}
public void setStartPos(int startPos) {
this.startPos = startPos;
}
/** 獲取下載的結束位置 */
public int getEndPos() {
return endPos;
}
public void setEndPos(int endPos) {
this.endPos = endPos;
}
/** 獲取已下載的大小 */
public int getCompeleteSize() {
return compeleteSize;
}
public void setCompeleteSize(int compeleteSize) {
this.compeleteSize = compeleteSize;
}
@Override
public String toString() {
return "DownloadInfo [threadId=" + threadId + ", startPos=" + startPos
+ ", endPos=" + endPos + ", compeleteSize=" + compeleteSize
+ "]";
}
}
下載實體類，針對於單個下載線程，保存下載線程對應的文件相關信息，比如當前下載線程負責下載的部分是從文件的哪個點開始的（startPos）、哪個點結束的（endPos）以及當前已經下載了多少（compeleteSize）等信息。
DownloadingInfo.java
package com.example.test;
/**
* 某一任務正在下載時的信息
*
* @author [email protected]
*
*/
public class DownloadingInfo {
private String kbps = "0"; // 每秒下載速度
private int secondSize = 0; // 一秒鐘累計下載量
private int fileSize = 0; // 文件大小
public String getKbps() {
return kbps;
}
public void setKbps(String kbps) {
this.kbps = kbps;
}
public int getSecondSize() {
return secondSize;
}
public void setSecondSize(int secondSize) {
this.secondSize = secondSize;
}
public int getFileSize() {
return fileSize;
}
public void setFileSize(int fileSize) {
this.fileSize = fileSize;
}
@Override
public String toString() {
return "DownloadingInfo [kbps=" + kbps + ", secondSize=" + secondSize
+ ", fileSize=" + fileSize + "]";
}
}
這也是一個下載相關的實體類，針對於一個下載任務（包括多個下載線程）。保存下載任務的下載進度、速度等用於客戶端顯示的數據。
DownloadHttpTool.java
package com.example.test;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
/**
* 利用Http協議進行多線程下載具體實現類
*
* @author [email protected]
*/
public class DownloadHttpTool {
private final int THREAD_COUNT = 2; // 線程數量
private String urlstr = ""; // URL地址
private Context mContext = null;
private List<DownloadInfo> downloadInfos = null; // 保存下載信息的類
/** 下載文件保存路徑 */
public static String filePath = ""; // 目錄
private String fileName = ""; // 文件名
private String fileNameTmp = ""; // 臨時文件名
/** 臨時文件名後綴 */
public static final String FILE_TMP_SUFFIX = ".tmp";
private int fileSize = 0; // 文件大小
private DownlaodSqlTool sqlTool = null; // 文件信息保存的數據庫操作類
private DownloadComplated downloadComplated = null;
private int totalCompelete = 0;// 所有線程已下載的總數
private List<DownloadThread> threads = null; // 下載線程
private Handler handler = null;
// 利用枚舉表示下載的幾種狀態
private enum Download_State {
Downloading, Pause, Ready, Compeleted, Exception;
}
private Download_State state = Download_State.Ready; // 當前下載狀態
/**
* @param context
* 上下文對象
* @param downloadComplated
*/
public DownloadHttpTool(Context context, Handler handler,
DownloadComplated downloadComplated) {
super();
this.mContext = context;
this.handler = handler;
this.downloadComplated = downloadComplated;
sqlTool = DownlaodSqlTool.getInstance(mContext);
if ("".equals(filePath)) {
// TODO 根據有無sdcard設置路徑
filePath = Environment.getExternalStorageDirectory()
.getAbsolutePath() + "/meiriq-download";
}
threads = new ArrayList<DownloadThread>();
}
/**
* 開始下載
*
* @param url
* 下載地址
*/
public void start(String urlstr) {
this.urlstr = urlstr;
String[] ss = urlstr.split("/");
fileName = ss[ss.length - 1];
fileNameTmp = fileName + FILE_TMP_SUFFIX;
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... arg0) {
// 下載之前首先異步線程調用ready方法做下載的準備工作
ready();
Message msg = new Message();
msg.what = 1;
msg.arg1 = fileSize;
msg.obj = DownloadHttpTool.this.urlstr;
handler.sendMessage(msg);
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// 開始下載
startDownload();
}
}.execute();
}
/** 在開始下載之前需要調用ready方法進行配置 */
private void ready() {
if (new File(filePath + "/" + fileName).exists()) {
downloadComplated.onComplated(urlstr);
return;
}
totalCompelete = 0;
downloadInfos = sqlTool.getInfos(urlstr);
if (downloadInfos.size() == 0) { // 數據庫中沒有相關信息
initFirst();
} else {
File file = new File(filePath + "/" + fileNameTmp);
if (!file.exists()) {
sqlTool.delete(urlstr);
initFirst();
} else {
fileSize = downloadInfos.get(downloadInfos.size() - 1)
.getEndPos();
for (DownloadInfo info : downloadInfos) {
totalCompelete += info.getCompeleteSize();
}
}
}
}
/** 開始下載 */
private void startDownload() {
if (downloadInfos != null) {
if (state == Download_State.Downloading) {
return;
}
state = Download_State.Downloading;
for (DownloadInfo info : downloadInfos) { // 開啓線程下載
DownloadThread thread = new DownloadThread(info.getThreadId(),
info.getStartPos(), info.getEndPos(),
info.getCompeleteSize(), info.getUrl());
thread.start();
threads.add(thread);
}
}
}
/** 暫停當前下載任務 */
public void pause() {
state = Download_State.Pause;
}
/** 刪除當前下載任務 */
public void delete() {
compeleted();
File file = new File(filePath + "/" + fileNameTmp);
file.delete();
}
/** 完成下載 */
private void compeleted() {
state = Download_State.Compeleted;
sqlTool.delete(urlstr);
downloadComplated.onComplated(urlstr);
}
/** 獲取目標文件大小 */
public int getFileSize() {
return fileSize;
}
/** 獲取當前下載的大小 */
public int getTotalCompeleteSize() {
return totalCompelete;
}
/** 第一次下載時進行的初始化 */
private void initFirst() {
URL url = null;
RandomAccessFile accessFile = null;
HttpURLConnection connection = null;
try {
url = new URL(urlstr);
connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(5000);
connection.setRequestMethod("GET");
fileSize = connection.getContentLength();
if (fileSize < 0) {
return;
}
File fileParent = new File(filePath);
if (!fileParent.exists()) {
fileParent.mkdir();
}
File file = new File(fileParent, fileNameTmp);
if (!file.exists()) {
file.createNewFile();
}
// 隨機訪問文件
accessFile = new RandomAccessFile(file, "rwd");
accessFile.setLength(fileSize);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (accessFile != null) {
try {
accessFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (connection != null) {
connection.disconnect();
}
}
// 計算每個線程需要下載的大小
int range = fileSize / THREAD_COUNT;
// 保存每個線程的下載信息
downloadInfos = new ArrayList<DownloadInfo>();
for (int i = 0; i < THREAD_COUNT - 1; i++) {
DownloadInfo info = new DownloadInfo(i, i * range, (i + 1) * range
- 1, 0, urlstr);
downloadInfos.add(info);
}
// 最後一個線程和前面的處理有點不一樣
DownloadInfo info = new DownloadInfo(THREAD_COUNT - 1,
(THREAD_COUNT - 1) * range, fileSize - 1, 0, urlstr);
downloadInfos.add(info);
// 插入到數據庫
sqlTool.insertInfos(downloadInfos);
}
interface DownloadComplated {
/**
* 下載完成回調
*
* @param urlString
*/
void onComplated(String urlString);
}
/** 自定義下載線程 */
private class DownloadThread extends Thread {
private int threadId = 0; // 線程Id
private int startPos = 0; // 在文件中的開始的位置
private int endPos = 0; // 在文件中的結束的位置
private int compeleteSize = 0; // 已完成下載的大小
private String urlstr = ""; // 下載地址
/**
*
* @param threadId
* 線程Id
* @param startPos
* 在文件中的開始的位置
* @param endPos
* 在文件中的結束的位置
* @param compeleteSize
* 已完成下載的大小
* @param urlstr
* 下載地址
*/
public DownloadThread(int threadId, int startPos, int endPos,
int compeleteSize, String urlstr) {
this.threadId = threadId;
this.startPos = startPos;
this.endPos = endPos;
this.urlstr = urlstr;
this.compeleteSize = compeleteSize;
}
@Override
public void run() {
HttpURLConnection connection = null;
RandomAccessFile randomAccessFile = null;
InputStream is = null;
try {
randomAccessFile = new RandomAccessFile(filePath + "/"
+ fileNameTmp, "rwd");
randomAccessFile.seek(startPos + compeleteSize);
URL url = new URL(urlstr);
connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(5000);
connection.setRequestMethod("GET");
// 設置請求的數據的範圍
connection.setRequestProperty("Range", "bytes="
+ (startPos + compeleteSize) + "-" + endPos);
is = connection.getInputStream();
byte[] buffer = new byte[6 * 1024]; // 6K的緩存
int length = -1;
while ((length = is.read(buffer)) != -1) {
randomAccessFile.write(buffer, 0, length); // 寫緩存數據到文件
compeleteSize += length;
synchronized (this) { // 加鎖保證已下載的正確性
totalCompelete += length;
Message msg = new Message();
msg.what = 0;
msg.arg1 = length;
msg.arg2 = totalCompelete;
msg.obj = urlstr;
handler.sendMessage(msg);
}
// 非正在下載狀態時跳出循環
if (state != Download_State.Downloading) {
break;
}
}
} catch (Exception e) {
e.printStackTrace();
System.out.println("異常退出____" + urlstr);
state = Download_State.Exception;
} finally {
// 不管發生了什麼事，都要保存下載信息到數據庫
sqlTool.updataInfos(threadId, compeleteSize, urlstr);
if (threads.size() == 1) { // 當前線程是此url對應下載任務唯一一個正在執行的線程
try {
if (is != null) {
is.close();
}
if (randomAccessFile != null) {
randomAccessFile.close();
}
if (connection != null) {
connection.disconnect();
}
} catch (Exception e) {
e.printStackTrace();
}
if (state == Download_State.Downloading) { // 此時此線程的下載任務正常完成（沒有被人爲或異常中斷）
File file = new File(filePath + "/" + fileNameTmp);
file.renameTo(new File(filePath + "/" + fileName));
}
if (state != Download_State.Pause) {
compeleted();
}
}
threads.remove(this);
}
}
}
}一個DownloadHttpTool的實例表示一個下載任務，一個下載任務中可以有多個下載線程，可以通過修改常量THREAD_COUNT的方式修改一個下載任務的下載線程數。文件的保存路徑是在sdcard中的meiriq-download文件夾，也可以修改到其他路徑。
此類中在下載開始的時候首先會執行ready()方法獲取文件相關的信息，之後執行startDownload()開啓下載線程執行下載。
下載時使用HttpURLConnection類的setRequestProperty方法指定請求頭字段實現文件的隨機下載（下載從某一個點開始到某一個點結束之際的內容），使用RandomAccessFile實現文件的隨機訪問（可以從某一個點開始寫入數據）。
爲了保證下載速度，寫入數據庫的操作並不是每次寫入文件之後都執行，而是在下載出現異常或者暫停等操作之後才寫入數據庫。所有下載任務全部結束後執行關閉數據流等操作。
DownloadUtil.java
package com.example.test;
import java.io.File;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import com.example.test.DownloadHttpTool.DownloadComplated;
/**
* 將下載方法封裝在此類 提供開始、暫停、刪除以及重置的方法。<br>
* 通過修改常量{@link DownloadUtil#MAX_COUNT}可改變最大並行下載任務量
*
* @author [email protected]
*/
public class DownloadUtil {
private static DownloadUtil instance = null;
private Context context = null;
private List<String> downloadList = null;
private Map<String, DownloadHttpTool> downloadMap = null;
private int currentUrlIndex = -1;
private final int MAX_COUNT = 2; // 最大並行下載量
private int currentCount = 0; // 當前並行下載量
private final String FLAG_FREE = "free"; // 標記downloadMap中空閒的DownloadHttpTool實例
private OnDownloadListener onDownloadListener = null;
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
String url = msg.obj.toString();
if (msg.what == 0) {
if (onDownloadListener != null) {
onDownloadListener
.downloadProgress(url, msg.arg2, msg.arg1);
}
} else if (msg.what == 1) {
if (onDownloadListener != null) {
onDownloadListener.downloadStart(url, msg.arg1);
}
} else if (msg.what == 2) {
onDownloadListener.downloadEnd(url);
}
}
};
private DownloadUtil(Context context) {
this.context = context;
downloadList = new ArrayList<String>();
downloadMap = new HashMap<String, DownloadHttpTool>();
}
private static synchronized void syncInit(Context context) {
if (instance == null) {
instance = new DownloadUtil(context);
}
}
public static DownloadUtil getInstance(Context context) {
if (instance == null) {
syncInit(context);
}
return instance;
}
/**
* 下載之前的準備工作，並自動開始下載
*
* @param context
*/
public void prepare(String urlString) {
downloadList.add(urlString);
if (currentCount < MAX_COUNT) {
start();
} else {
System.out.println("等待下載____" + urlString);
}
}
/**
* 開始下載
*/
private synchronized void start() {
if (++currentUrlIndex >= downloadList.size()) {
currentUrlIndex--;
return;
}
currentCount++;
String urlString = downloadList.get(currentUrlIndex);
System.out.println("開始下載____" + urlString);
DownloadHttpTool downloadHttpTool = null;
if (downloadMap.size() < MAX_COUNT) { // 保證downloadMap.size() <= 2
downloadHttpTool = new DownloadHttpTool(context, mHandler,
downloadComplated);
if (downloadMap.containsKey(urlString)) {
downloadMap.remove(urlString);
}
downloadMap.put(urlString, downloadHttpTool);
} else {
downloadHttpTool = downloadMap.get(FLAG_FREE);
downloadMap.remove(FLAG_FREE);
downloadMap.put(urlString, downloadHttpTool);
}
downloadHttpTool.start(urlString);
}
/** 暫停當前下載任務 */
public void pause(String urlString) {
paused(urlString, new Paused() {
@Override
public void onPaused(DownloadHttpTool downloadHttpTool) {
downloadHttpTool.pause();
}
});
}
/** 暫停所有的下載任務 */
public void pauseAll() {
// 如果需要邊遍歷集合邊刪除數據，需要從後向前遍歷，否則會出異常（Caused by:
// java.util.ConcurrentModificationException）
String[] keys = new String[downloadMap.size()];
downloadMap.keySet().toArray(keys);
for (int i = keys.length - 1; i >= 0; i--) {
pause(keys[i]);
}
instance = null;
}
/**
* 恢復當前下載任務
*
* @param urlString
* 要恢復下載的文件的地址
*/
public void resume(String urlString) {
prepare(urlString);
}
/** 恢復所有的下載任務 */
public void resumeAll() {
for (Entry<String, DownloadHttpTool> entity : downloadMap.entrySet()) {
prepare(entity.getKey());
}
}
/** 刪除當前下載任務 */
public void delete(String urlString) {
boolean bool = paused(urlString, new Paused() {
@Override
public void onPaused(DownloadHttpTool downloadHttpTool) {
downloadHttpTool.pause();
downloadHttpTool.delete();
}
});
if (!bool) { // 下載任務不存在，直接刪除臨時文件
File file = new File(DownloadHttpTool.filePath + "/"
+ urlString.split("/")[urlString.split("/").length - 1]
+ DownloadHttpTool.FILE_TMP_SUFFIX);
System.out.println(file.delete());
}
}
interface Paused {
void onPaused(DownloadHttpTool downloadHttpTool);
}
/**
* 暫停
*
* @param urlString
* @param paused
* @return 下載任務是否存在的標識
*/
private boolean paused(String urlString, Paused paused) {
if (downloadMap.containsKey(urlString)) {
currentCount--;
DownloadHttpTool downloadHttpTool = downloadMap.get(urlString);
paused.onPaused(downloadHttpTool);
if (!downloadMap.containsKey(FLAG_FREE)) { // 保證key == FLAG_FREE的數量
// = 1
downloadMap.put(FLAG_FREE, downloadHttpTool);
}
downloadMap.remove(urlString);
start();
return true;
}
return false;
}
DownloadComplated downloadComplated = new DownloadComplated() {
@Override
public void onComplated(String urlString) {
System.out.println("下載完成____" + urlString);
Message msg = new Message();
msg.what = 2;
msg.obj = urlString;
mHandler.sendMessage(msg);
pause(urlString);
// 滿足此條件說明全部下載結束
if (downloadMap.size() == 1 && downloadMap.containsKey(FLAG_FREE)) {
System.out.println("全部下載結束");
}
}
};
/** 設置下載監聽 */
public void setOnDownloadListener(OnDownloadListener onDownloadListener) {
this.onDownloadListener = onDownloadListener;
}
/** 下載回調接口 */
public interface OnDownloadListener {
/**
* 下載開始回調接口
*
* @param url
* @param fileSize
* 目標文件大小
*/
public void downloadStart(String url, int fileSize);
/**
* 下載進度回調接口
*
* @param
* @param downloadedSize
* 已下載大小
* @param lenth
* 本次下載大小
*/
public void downloadProgress(String url, int downloadedSize, int length);
/**
* 下載完成回調
*
* @param url
*/
public void downloadEnd(String url);
}
}一個單例的類封了”開始“、”暫停“、”繼續“、”刪除“等下載任務相關操作方法，管理所有下載任務；利用Handler實現下載進度等信息的更新；常量FLAG_FREE標識空閒下載任務；可通過修改常量MAX_COUNT的值的方式修改最大並行下載任務數。
該類管理下載任務的方式：獲取該類實例後調用prepare(String urlString)方法添加下載任務，如果沒有達到最大並行下載數，則會執行start()開始下載，否則等待其他下載任務下載完成後下載；當一個任務被暫停、刪除或者下載完成後執行start()開始新的下載。集合downloadMap保存所有的下載任務，最多MAX_COUNT個。當一個下載任務完成後downloadMap中對應的下載任務變爲FLAG_FREE以便後來的任務重複使用，如果FLAG_FREE的任務已存在則直接刪除此任務。
MainActivity.java
package com.example.test;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Timer;
import java.util.TimerTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.example.test.DownloadUtil.OnDownloadListener;
public class MainActivity extends FragmentActivity implements OnClickListener {
private ListView listView = null;
private List<String> urls = null;
private DownloadUtil downloadUtil = null;
private final String TAG_PROGRESS = "_progress";
private final String TAG_TOTAL = "_total";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listview);
urls = new ArrayList<String>();
urls.add("http://pc1.gamedog.cn/big/game/dongzuo/102631/shenmiaotw2_yxdog.apk");
urls.add("http://pc1.gamedog.cn/big/game/yizhi/67450/baoweiluobo_an_yxdog.apk");
urls.add("http://pc1.gamedog.cn/big/game/yizhi/161623/zhiwudzjs2gqb_an.apk");
listView.setAdapter(myAdapter);
downloadUtil = DownloadUtil.getInstance(this);
downloadUtil.setOnDownloadListener(new OnDownloadListener() {
String text = "已下載%sM / 共%sM \n佔比%s \n下載速度%skb/s";
DecimalFormat decimalFormat = new DecimalFormat("#.##"); // 小數格式化
Timer timer = null;
Map<String, DownloadingInfo> downloadingInfos = new HashMap<String, DownloadingInfo>();
@Override
public void downloadStart(String url, int fileSize) {
DownloadingInfo info = new DownloadingInfo();
info.setFileSize(fileSize);
downloadingInfos.put(url, info);
((ProgressBar) listView.findViewWithTag(url + TAG_PROGRESS))
.setMax(fileSize);
}
@Override
public synchronized void downloadProgress(String url,
int downloadedSize, int length) {
DownloadingInfo info = downloadingInfos.get(url);
if (info != null) {
((ProgressBar) listView.findViewWithTag(url + TAG_PROGRESS))
.setProgress(downloadedSize);
((TextView) listView.findViewWithTag(url + TAG_TOTAL)).setText(String.format(
text,
decimalFormat
.format(downloadedSize / 1024.0 / 1024.0),
decimalFormat.format(info.getFileSize() / 1024.0 / 1024.0),
(int) (((float) downloadedSize / (float) info
.getFileSize()) * 100) + "%", info
.getKbps()));
info.setSecondSize(info.getSecondSize() + length);
}
if (timer == null) {
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
DownloadingInfo info = null;
for (Entry<String, DownloadingInfo> entry : downloadingInfos
.entrySet()) {
info = entry.getValue();
if (info != null) {
info.setKbps(decimalFormat.format(info
.getSecondSize() / 1024.0));
info.setSecondSize(0);
}
}
}
}, 0, 1000);
}
}
@Override
public void downloadEnd(String url) {
DownloadingInfo info = downloadingInfos.get(url);
if (info != null) {
((ProgressBar) listView.findViewWithTag(url + TAG_PROGRESS))
.setProgress(info.getFileSize());
((TextView) listView.findViewWithTag(url + TAG_TOTAL))
.setText(String.format(
text,
decimalFormat.format(info.getFileSize() / 1024.0 / 1024.0),
decimalFormat.format(info.getFileSize() / 1024.0 / 1024.0),
"100%", info.getKbps()));
downloadingInfos.remove(url);
}
}
});
}
BaseAdapter myAdapter = new BaseAdapter() {
@Override
public View getView(int position, View convertView, ViewGroup parent) {
Holder holder = null;
if (convertView == null) {
convertView = LayoutInflater.from(MainActivity.this).inflate(
R.layout.list_item, null);
holder = new Holder();
holder.tv_url = (TextView) convertView.findViewById(R.id.url);
holder.progressBar = (ProgressBar) convertView
.findViewById(R.id.progressBar);
holder.textView_total = (TextView) convertView
.findViewById(R.id.textView_total);
holder.button_start = (Button) convertView
.findViewById(R.id.button_start);
holder.button_pause = (Button) convertView
.findViewById(R.id.button_pause);
holder.button_resume = (Button) convertView
.findViewById(R.id.button_resume);
holder.button_delete = (Button) convertView
.findViewById(R.id.button_delete);
convertView.setTag(holder);
setClick(holder);
} else {
holder = (Holder) convertView.getTag();
}
holder.tv_url.setText(urls.get(position));
holder.progressBar.setTag(urls.get(position) + TAG_PROGRESS);
holder.textView_total.setTag(urls.get(position) + TAG_TOTAL);
holder.button_start.setTag(urls.get(position));
holder.button_pause.setTag(urls.get(position));
holder.button_resume.setTag(urls.get(position));
holder.button_delete.setTag(urls.get(position));
return convertView;
}
private void setClick(Holder holder) {
holder.button_start.setOnClickListener(MainActivity.this);
holder.button_pause.setOnClickListener(MainActivity.this);
holder.button_resume.setOnClickListener(MainActivity.this);
holder.button_delete.setOnClickListener(MainActivity.this);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public Object getItem(int position) {
return urls.get(position);
}
@Override
public int getCount() {
return urls.size();
}
class Holder {
TextView tv_url = null;
ProgressBar progressBar = null;
TextView textView_total = null;
Button button_start = null;
Button button_pause = null;
Button button_resume = null;
Button button_delete = null;
}
};
@Override
public void onClick(View view) {
String url = view.getTag() == null ? "" : view.getTag().toString();
switch (view.getId()) {
case R.id.button_start:
downloadUtil.prepare(url);
break;
case R.id.button_pause:
downloadUtil.pause(url);
break;
case R.id.button_resume:
downloadUtil.resume(url);
break;
case R.id.button_delete:
downloadUtil.delete(url);
break;
default:
break;
}
}
}使用ListView展示待下載任務列表。使用List<String>集合urls保存下載地址。使用View.setTag(url+TAG_PROGRESS/TAG_TOTAL)的方式標記各個任務對應的View。在顯示數據的時候使用findViewWithTag(url+TAG_PROGRESS/TAG_TOTAL)的方式取得對應的View；使用Timer定時器，每隔1s刷新一次下載速度。
activity_main.xml
<LinearLayout xmlns:tools="http://schemas.android.com/tools"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<ListView
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</LinearLayout>list_item.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="10dp" >
<TextView
android:id="@+id/url"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<ProgressBar
android:id="@+id/progressBar"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/url" />
<TextView
android:id="@+id/textView_total"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/progressBar"
android:layout_margin="10dp"
android:lines="3"
android:text="下載進度" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/textView_total" >
<Button
android:id="@+id/button_start"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="開始"
android:textSize="12sp" />
<Button
android:id="@+id/button_pause"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="暫停"
android:textSize="12sp" />
<Button
android:id="@+id/button_resume"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="繼續"
android:textSize="12sp" />
<Button
android:id="@+id/button_delete"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="刪除"
android:textSize="12sp" />
</LinearLayout>
</RelativeLayout>最後添加連接網絡和操作sdcard的權限：
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />此代碼是使用數據庫和RandomAccessFile類實現斷點下載，除此方法外，還可以用臨時文件的方式實現斷點下載，具體方法：同以上代碼使用HttpURLConnection和setRequestProperty方法實現文件的部分下載，然後每一部分保存爲一個臨時文件，待全部下載完成後，將所有相關臨時文件寫入到一個文件，並刪除臨時文件即可。