[置顶] android 多线程断点续传下载 四 - 仿下载助手

我们先一起简单回顾下它的基本原理。

http://blog.csdn.net/shimiso/article/details/6763664  android 多线程断点续传下载 一

http://blog.csdn.net/shimiso/article/details/6763986  android 多线程断点续传下载 二

http://blog.csdn.net/shimiso/article/details/8448544  android 多线程断点续传下载 三

界面效果

线程池 ThreadPoolExecutor

在下面介绍实现下载原理的时候，我想尝试倒着来说，这样是否好理解一点？ 
我们都知道，下载助手，比如360， 百度的 手机助手，下载APP 的时候 ，都可以同时下载多个，所以，下载肯定是多线程的，所以我们就需要一个线程工具类 来管理我们的线程，这个工具类的核心，就是 线程池。 
线程池ThreadPoolExecutor ，先简单学习下这个线程池的使用

01. /**
02. * Parameters:
03. corePoolSize
04. the number of threads to keep in the pool, even if they are idle, unless allowCoreThreadTimeOut is set
05. maximumPoolSize
06. the maximum number of threads to allow in the pool
07. keepAliveTime
08. when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.
09. unit
10. the time unit for the keepAliveTime argument
11. workQueue
12. the queue to use for holding tasks before they are executed. This queue will hold only the Runnable tasks submitted                   by the execute method.
13. handler
14. the handler to use when execution is blocked because the thread bounds and queue capacities are reached
15. Throws:
16. IllegalArgumentException - if one of the following holds:
17. corePoolSize < 0
18. keepAliveTime < 0
19. maximumPoolSize <= 0
20. maximumPoolSize < corePoolSize
21. NullPointerException - if workQueue or handler is null
22. */
23. ThreadPoolExecutor threadpool=new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, hand

上面是 ThreadPoolExecutor的参数介绍， 

第一个参数 corePoolSize ： 空闲时 存在的线程数目、 
第二个参数 maximumPoolSize ：允许同时存在的最大线程数、 
第三个参数 keepAliveTime： 这个参数是 允许空闲线程存活的时间、 
第四个参数 unit ： 是 时间的单位 、 
第五个参数 workQueue ：这个是一个容器，它里面存放的是、 threadpool.execute(new Runnable()) 执行的线程.new Runnable()、 
第六个参数 handler：当执行被阻塞时，该处理程序将被阻塞，因为线程的边界和队列容量达到了 。

工具类 ThreadManager

介绍完了 线程池参数，那我们就先创建一个线程管理的工具类 ThreadManager

001. public class ThreadManager {
002. public static final String DEFAULT_SINGLE_POOL_NAME = "DEFAULT_SINGLE_POOL_NAME";
003.
004. private static ThreadPoolProxy mLongPool = null;
005. private static Object mLongLock = new Object();
006.
007. private static ThreadPoolProxy mShortPool = null;
008. private static Object mShortLock = new Object();
009.
010. private static ThreadPoolProxy mDownloadPool = null;
011. private static Object mDownloadLock = new Object();
012.
013. private static Map<String, ThreadPoolProxy> mMap = new HashMap<String, ThreadPoolProxy>();
014. private static Object mSingleLock = new Object();
015.
016. /** 获取下载线程 */
017. public static ThreadPoolProxy getDownloadPool() {
018. synchronized (mDownloadLock) {
019. if (mDownloadPool == null) {
020. mDownloadPool = new ThreadPoolProxy(3, 3, 5L);
021. }
022. return mDownloadPool;
023. }
024. }
025.
026. /** 获取一个用于执行长耗时任务的线程池，避免和短耗时任务处在同一个队列而阻塞了重要的短耗时任务，通常用来联网操作 */
027. public static ThreadPoolProxy getLongPool() {
028. synchronized (mLongLock) {
029. if (mLongPool == null) {
030. mLongPool = new ThreadPoolProxy(5, 5, 5L);
031. }
032. return mLongPool;
033. }
034. }
035.
036. /** 获取一个用于执行短耗时任务的线程池，避免因为和耗时长的任务处在同一个队列而长时间得不到执行，通常用来执行本地的IO/SQL */
037. public static ThreadPoolProxy getShortPool() {
038. synchronized (mShortLock) {
039. if (mShortPool == null) {
040. mShortPool = new ThreadPoolProxy(2, 2, 5L);
041. }
042. return mShortPool;
043. }
044. }
045.
046. /** 获取一个单线程池，所有任务将会被按照加入的顺序执行，免除了同步开销的问题 */
047. public static ThreadPoolProxy getSinglePool() {
048. return getSinglePool(DEFAULT_SINGLE_POOL_NAME);
049. }
050.
051. /** 获取一个单线程池，所有任务将会被按照加入的顺序执行，免除了同步开销的问题 */
052. public static ThreadPoolProxy getSinglePool(String name) {
053. synchronized (mSingleLock) {
054. ThreadPoolProxy singlePool = mMap.get(name);
055. if (singlePool == null) {
056. singlePool = new ThreadPoolProxy(1, 1, 5L);
057. mMap.put(name, singlePool);
058. }
059. return singlePool;
060. }
061. }
062.
063. public static class ThreadPoolProxy {
064. private ThreadPoolExecutor mPool;
065. private int mCorePoolSize;
066. private int mMaximumPoolSize;
067. private long mKeepAliveTime;
068.
069. private ThreadPoolProxy(int corePoolSize, int maximumPoolSize, long keepAliveTime) {
070. mCorePoolSize = corePoolSize;
071. mMaximumPoolSize = maximumPoolSize;
072. mKeepAliveTime = keepAliveTime;
073. }
074.
075. /** 执行任务，当线程池处于关闭，将会重新创建新的线程池 */
076. public synchronized void execute(Runnable run) {
077. if (run == null) {
078. return;
079. }
080. if (mPool == null || mPool.isShutdown()) {
081. mPool = new ThreadPoolExecutor(mCorePoolSize, mMaximumPoolSize, mKeepAliveTime, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(), Executors.defaultThreadFactory(), new AbortPolicy());
082. }
083. mPool.execute(run);
084. }
085.
086. /** 取消线程池中某个还未执行的任务 */
087. public synchronized void cancel(Runnable run) {
088. if (mPool != null && (!mPool.isShutdown() || mPool.isTerminating())) {
089. mPool.getQueue().remove(run);
090. }
091. }
092.
093. /** 取消线程池中某个还未执行的任务 */
094. public synchronized boolean contains(Runnable run) {
095. if (mPool != null && (!mPool.isShutdown() || mPool.isTerminating())) {
096. return mPool.getQueue().contains(run);
097. } else {
098. return false;
099. }
100. }
101.
102. /** 立刻关闭线程池，并且正在执行的任务也将会被中断 */
103. public void stop() {
104. if (mPool != null && (!mPool.isShutdown() || mPool.isTerminating())) {
105. mPool.shutdownNow();
106. }
107. }
108.
109. /** 平缓关闭单任务线程池，但是会确保所有已经加入的任务都将会被执行完毕才关闭 */
110. public synchronized void shutdown() {
111. if (mPool != null && (!mPool.isShutdown() || mPool.isTerminating())) {
112. mPool.shutdownNow();
113. }
114. }
115.
116. }
117. }

这个线程池工具类 主要就是 生成一个线程池， 以及 取消线程池中的任务，查询线程池中是否包含某一任务。

下载任务 DownloadTask

我们的现在线程 DownloadTask 就 通过 ThreadManager .getDownloadPool（）.execute() 方法 交给线程池去管理。

有了线程池管理我们的线程， 那我们下一步 就是 DownloadTask 这个类去下载了。

01. /** 下载任务 */
02. public class DownloadTask implements Runnable {
03. private DownloadInfo info;
04.
05. public DownloadTask(DownloadInfo info) {
06. this.info = info;
07. }
08.
09. @Override
10. public void run() {
11. info.setDownloadState(STATE_DOWNLOADING);// 先改变下载状态
12. notifyDownloadStateChanged(info);
13. File file = new File(info.getPath());// 获取下载文件
14. HttpResult httpResult = null;
15. InputStream stream = null;
16. if (info.getCurrentSize() == 0 || !file.exists()
17. || file.length() != info.getCurrentSize()) {
18. // 如果文件不存在，或者进度为0，或者进度和文件长度不相符，就需要重新下载
19.
20. info.setCurrentSize(0);
21. file.delete();
22. }
23. httpResult = HttpHelper.download(info.getUrl());
24. // else {
25. // // //文件存在且长度和进度相等，采用断点下载
26. // httpResult = HttpHelper.download(info.getUrl() + "&range=" +
27. // info.getCurrentSize());
28. // }
29. if (httpResult == null
30. || (stream = httpResult.getInputStream()) == null) {
31. info.setDownloadState(STATE_ERROR);// 没有下载内容返回，修改为错误状态
32. notifyDownloadStateChanged(info);
33. } else {
34. try {
35. skipBytesFromStream(stream, info.getCurrentSize());
36. } catch (Exception e1) {
37. e1.printStackTrace();
38. }
39.
40. FileOutputStream fos = null;
41. try {
42. fos = new FileOutputStream(file, true);
43. int count = -1;
44. byte[] buffer = new byte[1024];
45. while (((count = stream.read(buffer)) != -1)
46. && info.getDownloadState() == STATE_DOWNLOADING) {
47. // 每次读取到数据后，都需要判断是否为下载状态，如果不是，下载需要终止，如果是，则刷新进度
48. fos.write(buffer, 0, count);
49. fos.flush();
50. info.setCurrentSize(info.getCurrentSize() + count);
51. notifyDownloadProgressed(info);// 刷新进度
52. }
53. } catch (Exception e) {
54. info.setDownloadState(STATE_ERROR);
55. notifyDownloadStateChanged(info);
56. info.setCurrentSize(0);
57. file.delete();
58. } finally {
59. IOUtils.close(fos);
60. if (httpResult != null) {
61. httpResult.close();
62. }
63. }
64.
65. // 判断进度是否和app总长度相等
66. if (info.getCurrentSize() == info.getAppSize()) {
67. info.setDownloadState(STATE_DOWNLOADED);
68. notifyDownloadStateChanged(info);
69. } else if (info.getDownloadState() == STATE_PAUSED) {// 判断状态
70. notifyDownloadStateChanged(info);
71. } else {
72. info.setDownloadState(STATE_ERROR);
73. notifyDownloadStateChanged(info);
74. info.setCurrentSize(0);// 错误状态需要删除文件
75. file.delete();
76. }
77. }
78. mTaskMap.remove(info.getId());
79. }
80. }

下载的原理 很简单，就是 通过 目标的URL 拿到流，然后写到本地。 

因为下载在 run（） 里面执行，这个DownloadTask 类 我们就看run() 方法的实现，所以 关键代码 就是下面一点点

01. fos = new FileOutputStream(file, true);
02. int count = -1;
03. byte[] buffer = new byte[1024];
04. while (((count = stream.read(buffer)) != -1)
05. && info.getDownloadState() == STATE_DOWNLOADING) {
06. // 每次读取到数据后，都需要判断是否为下载状态，如果不是，下载需要终止，如果是，则刷新进度
07. fos.write(buffer, 0, count);
08. fos.flush();
09. info.setCurrentSize(info.getCurrentSize() + count);
10. notifyDownloadProgressed(info);// 刷新进度
11. }

这个在我们刚接触Java 的时候 肯定都写过了。 这就是往本地写数据的代码。所以run（）方法中的 前面 就是拿到 stream 输入流， 以及 把file 创建出来。

刷新进度，状态

关于控制 button中text 显示 暂停 ，下载，还是进度，就靠 notifyDownloadProgressed(info);和 notifyDownloadStateChanged（info）两个方法， 这两个方法 实际上调用的是两个接口，只要我们在我们需要改变界面的类里 实现这两个接口，就可以接收到 包含最新信息的info对象。而我们在哪个类里改变button 上面 显示的文字呢？ 当然是在 我们的adapter 里面了，大家都知道 是在 adapter 的getView() 方法里面 加载的每一条数据的布局。

那就一起看下是不是这样子呢？

001. public class RecommendAdapter extends BaseAdapter implements
002. DownloadManager.DownloadObserver {
003.
004. ArrayList<AppInfo> list;
005. private List<ViewHolder> mDisplayedHolders;
006. private FinalBitmap finalBitmap;
007. private Context context;
008.
009. public RecommendAdapter(ArrayList<AppInfo> list, FinalBitmap finalBitmap,
010. Context context) {
011. this.list = list;
012. this.context = context;
013. this.finalBitmap = finalBitmap;
014. mDisplayedHolders = new ArrayList<ViewHolder>();
015. }
016.
017.
018.
019. public void startObserver() {
020. DownloadManager.getInstance().registerObserver(this);
021. }
022.
023. public void stopObserver() {
024. DownloadManager.getInstance().unRegisterObserver(this);
025. }
026.
027. @Override
028. public int getCount() {
029. return list.size();
030. }
031.
032. @Override
033. public Object getItem(int position) {
034. return list.get(position);
035. }
036.
037. @Override
038. public long getItemId(int position) {
039. return position;
040. }
041.
042. @Override
043. public View getView(int position, View convertView, ViewGroup parent) {
044. final AppInfo appInfo = list.get(position);
045. final ViewHolder holder;
046.
047. if (convertView == null) {
048. holder = new ViewHolder(context);
049. } else {
050. holder = (ViewHolder) convertView.getTag();
051. }
052. holder.setData(appInfo);
053. mDisplayedHolders.add(holder);
054. return holder.getRootView();
055. }
056.
057. @Override
058. public void onDownloadStateChanged(DownloadInfo info) {
059. refreshHolder(info);
060. }
061.
062. @Override
063. public void onDownloadProgressed(DownloadInfo info) {
064. refreshHolder(info);
065.
066. }
067.
068. public List<ViewHolder> getDisplayedHolders() {
069. synchronized (mDisplayedHolders) {
070. return new ArrayList<ViewHolder>(mDisplayedHolders);
071. }
072. }
073.
074. public void clearAllItem() {
075. if (list != null){
076. list.clear();
077. }
078. if (mDisplayedHolders != null) {
079. mDisplayedHolders.clear();
080. }
081. }
082.
083. public void addItems(ArrayList<AppInfo> infos) {
084. list.addAll(infos);
085. }
086.
087. private void refreshHolder(final DownloadInfo info) {
088. List<ViewHolder> displayedHolders = getDisplayedHolders();
089. for (int i = 0; i < displayedHolders.size(); i++) {
090. final ViewHolder holder = displayedHolders.get(i);
091. AppInfo appInfo = holder.getData();
092. if (appInfo.getId() == info.getId()) {
093. AppUtil.post(new Runnable() {
094. @Override
095. public void run() {
096. holder.refreshState(info.getDownloadState(),
097. info.getProgress());
098. }
099. });
100. }
101. }
102.
103. }
104.
105. public class ViewHolder {
106. public TextView textView01;
107. public TextView textView02;
108. public TextView textView03;
109. public TextView textView04;
110. public ImageView imageView_icon;
111. public Button button;
112. public LinearLayout linearLayout;
113.
114. public AppInfo mData;
115. private DownloadManager mDownloadManager;
116. private int mState;
117. private float mProgress;
118. protected View mRootView;
119. private Context context;
120. private boolean hasAttached;
121.
122. public ViewHolder(Context context) {
123. mRootView = initView();
124. mRootView.setTag(this);
125. this.context = context;
126.
127.
128. }
129.
130. public View getRootView() {
131. return mRootView;
132. }
133.
134. public View initView() {
135. View view = AppUtil.inflate(R.layout.item_recommend_award);
136.
137. imageView_icon = (ImageView) view
138. .findViewById(R.id.imageview_task_app_cion);
139.
140. textView01 = (TextView) view
141. .findViewById(R.id.textview_task_app_name);
142. textView02 = (TextView) view
143. .findViewById(R.id.textview_task_app_size);
144. textView03 = (TextView) view
145. .findViewById(R.id.textview_task_app_desc);
146. textView04 = (TextView) view
147. .findViewById(R.id.textview_task_app_love);
148. button = (Button) view.findViewById(R.id.button_task_download);
149. linearLayout = (LinearLayout) view
150. .findViewById(R.id.linearlayout_task);
151.
152. button.setOnClickListener(new OnClickListener() {
153. @Override
154. public void onClick(View v) {
155. System.out.println("mState:173    "+mState);
156. if (mState == DownloadManager.STATE_NONE
157. || mState == DownloadManager.STATE_PAUSED
158. || mState == DownloadManager.STATE_ERROR) {
159.
160. mDownloadManager.download(mData);
161. } else if (mState == DownloadManager.STATE_WAITING
162. || mState == DownloadManager.STATE_DOWNLOADING) {
163. mDownloadManager.pause(mData);
164. } else if (mState == DownloadManager.STATE_DOWNLOADED) {
165. //                      tell2Server();
166. mDownloadManager.install(mData);
167. }
168. }
169. });
170. return view;
171. }
172.
173.
174. public void setData(AppInfo data) {
175.
176. if (mDownloadManager == null) {
177. mDownloadManager = DownloadManager.getInstance();
178.
179. }
180. String filepath= FileUtil.getDownloadDir(AppUtil.getContext()) + File.separator + data.getName() + ".apk";
181.
182. boolean existsFile = FileUtil.isExistsFile(filepath);
183. if(existsFile){
184. int fileSize = FileUtil.getFileSize(filepath);
185.
186. if(data.getSize()==fileSize){
187. DownloadInfo downloadInfo = DownloadInfo.clone(data);
188. downloadInfo.setCurrentSize(data.getSize());
189. downloadInfo.setHasFinished(true);
190. mDownloadManager.setDownloadInfo(data.getId(),downloadInfo );
191. }
192. //                  else if(fileSize>0){
193. //                      DownloadInfo downloadInfo = DownloadInfo.clone(data);
194. //                      downloadInfo.setCurrentSize(data.getSize());
195. //                      downloadInfo.setHasFinished(false);
196. //                      mDownloadManager.setDownloadInfo(data.getId(),downloadInfo );
197. //                  }
198.
199. }
200.
201. DownloadInfo downloadInfo = mDownloadManager.getDownloadInfo(data
202. .getId());
203. if (downloadInfo != null) {
204.
205. mState = downloadInfo.getDownloadState();
206. mProgress = downloadInfo.getProgress();
207. } else {
208.
209. mState = DownloadManager.STATE_NONE;
210. mProgress = 0;
211. }
212. this.mData = data;
213. refreshView();
214. }
215.
216. public AppInfo getData() {
217. return mData;
218. }
219.
220. public void refreshView() {
221. linearLayout.removeAllViews();
222. AppInfo info = getData();
223. textView01.setText(info.getName());
224. textView02.setText(FileUtil.FormetFileSize(info.getSize()));
225. textView03.setText(info.getDes());
226. textView04.setText(info.getDownloadNum() + "下载量);
227. finalBitmap.display(imageView_icon, info.getIconUrl());
228.
229.
230. if (info.getType().equals("0")) {
231. //              mState = DownloadManager.STATE_READ;
232. textView02.setVisibility(View.GONE);
233. }else{
234. String  path=FileUtil.getDownloadDir(AppUtil.getContext()) + File.separator + info.getName() + ".apk";
235. hasAttached = FileUtil.isValidAttach(path, false);
236.
237. DownloadInfo downloadInfo = mDownloadManager.getDownloadInfo(info
238. .getId());
239. if (downloadInfo != null && hasAttached) {
240. if(downloadInfo.isHasFinished()){
241.
242. mState = DownloadManager.STATE_DOWNLOADED;
243. }else{
244. mState = DownloadManager.STATE_PAUSED;
245.
246. }
247.
248. } else {
249. mState = DownloadManager.STATE_NONE;
250. if(downloadInfo !=null){
251. downloadInfo.setDownloadState(mState);
252. }
253. }
254. }
255.
256. refreshState(mState, mProgress);
257. }
258.
259. public void refreshState(int state, float progress) {
260. mState = state;
261. mProgress = progress;
262. switch (mState) {
263. case DownloadManager.STATE_NONE:
264. button.setText(R.string.app_state_download);
265. break;
266. case DownloadManager.STATE_PAUSED:
267. button.setText(R.string.app_state_paused);
268. break;
269. case DownloadManager.STATE_ERROR:
270. button.setText(R.string.app_state_error);
271. break;
272. case DownloadManager.STATE_WAITING:
273. button.setText(R.string.app_state_waiting);
274. break;
275. case DownloadManager.STATE_DOWNLOADING:
276. button.setText((int) (mProgress * 100) + "%");
277. break;
278. case DownloadManager.STATE_DOWNLOADED:
279. button.setText(R.string.app_state_downloaded);
280. break;
281. //          case DownloadManager.STATE_READ:
282. //              button.setText(R.string.app_state_read);
283. //              break;
284. default:
285. break;
286. }
287. }
288. }
289. }

何时 注册 监听observer

里面代码有点多，那就看startObserver（）方法做了什么。

1. public void startObserver() {
2. DownloadManager.getInstance().registerObserver(this);
3. }

这里 是 注册了observer, Observer 是什么东西？在DownloadManager 中我们定义了 

1. public