多线程断点下载（开始下载，暂停下载，百分比进度条）

喜欢ヅ旅行 2022-08-20 12:22 156阅读 0赞

1.  **package** cn.itcast.download;  
2.    
3.  **import** java.io.File;  
4.  **import** java.io.FileInputStream;  
5.  **import** java.io.FileNotFoundException;  
6.  **import** java.io.FileOutputStream;  
7.  **import** java.io.IOException;  
8.  **import** java.io.InputStream;  
9.  **import** java.io.RandomAccessFile;  
10. **import** java.net.HttpURLConnection;  
11. **import** java.net.MalformedURLException;  
12. **import** java.net.ProtocolException;  
13. **import** java.net.URL;  
14.   
15. **import** cn.itcast.mutiledownload.StreamTool;  
16.   
17. **import** android.app.Activity;  
18. **import** android.os.Bundle;  
19. **import** android.os.Handler;  
20. **import** android.os.Message;  
21. **import** android.view.View;  
22. **import** android.view.View.OnClickListener;  
23. **import** android.widget.Button;  
24. **import** android.widget.EditText;  
25. **import** android.widget.ProgressBar;  
26. **import** android.widget.TextView;  
27. **import** android.widget.Toast;  
28.   
29. **public** **class** MutiledownloadActivity **extends** Activity **implements** OnClickListener \{  
30.   
31.     **private** ProgressBar pb;  
32.     **private** Button bt;  
33.     **private** TextView tv;  
34.     **private** EditText et;  
35.     **boolean** flag = **true**;  
36.     **boolean** stopflag = **false**;  
37.     **private** Handler handler = **new** Handler() \{  
38.   
39.         @Override  
40.         **public** **void** handleMessage(Message msg) \{  
41.             pb.setProgress(total);  
42.   
43.             **int** max = pb.getMax();  
44.             **if** (total >= (max - 1)) \{  
45.                 total = max;  
46.                 flag = **false**;  
47.             \}  
48.             **int** result = total \* 100 / max;  
49.             tv.setText("当前进度 :" + result + "%");  
50.   
51.             **super**.handleMessage(msg);  
52.         \}  
53.     \};  
54.   
55.     **int** total = 0;  
56.   
57.     @Override  
58.     **public** **void** onCreate(Bundle savedInstanceState) \{  
59.         **super**.onCreate(savedInstanceState);  
60.         setContentView(R.layout.main);  
61.         pb = (ProgressBar) **this**.findViewById(R.id.pb);  
62.         bt = (Button) **this**.findViewById(R.id.bt);  
63.         tv = (TextView) **this**.findViewById(R.id.tv\_process);  
64.         et = (EditText) **this**.findViewById(R.id.et);  
65.         bt.setOnClickListener(**this**);  
66.   
67.     \}  
68.   
69.     @Override  
70.     **public** **void** onClick(View v) \{  
71.         **switch** (v.getId()) \{  
72.         **case** R.id.bt:  
73.             // 创建一个子线程 定期的更新ui  
74.   
75.             **if**("开始下载".equals(bt.getText().toString()))\{  
76.                 bt.setText("暂停");  
77.                 stopflag = **false**; //开始下载   
78.             \}  
79.             **else** \{  
80.                 bt.setText("开始下载");  
81.                 stopflag = **true**;  
82.             \}  
83.                 **new** Thread() \{  
84.   
85.                     @Override  
86.                     **public** **void** run() \{  
87.                         **super**.run();  
88.                         **while** (flag) \{  
89.                             **try** \{  
90.                                 sleep(1000);  
91.                                 // 如果total > = 文件长度  
92.                                 Message msg = **new** Message();  
93.                                 handler.sendMessage(msg);  
94.                             \} **catch** (InterruptedException e) \{  
95.                                 e.printStackTrace();  
96.                             \}  
97.   
98.                         \}  
99.                     \}  
100.                 \}.start();  
101.   
102.                 // 开始执行下载的操作  
103.                 String path = et.getText().toString().trim();  
104.                 **if** ("".equals(path)) \{  
105.                     Toast.makeText(**this**, "路径不能为空", 1).show();  
106.                     **return**;  
107.                 \}  
108.                 **try** \{  
109.                     URL url = **new** URL(path);  
110.                     HttpURLConnection conn = (HttpURLConnection) url  
111.                             .openConnection();  
112.                     conn.setRequestMethod("GET");  
113.                     conn.setConnectTimeout(5000);  
114.                     conn.setRequestProperty("User-Agent",  
115.                             "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");  
116.                     **int** code = conn.getResponseCode();  
117.                     **if** (code == 200) \{  
118.                         **int** len = conn.getContentLength();  
119.                         RandomAccessFile file = **new** RandomAccessFile(  
120.                                 "/mnt/sdcard/" + getFilenName(path), "rwd");  
121.                         // 1.设置本地文件大小跟服务器的文件大小一致  
122.                         file.setLength(len);  
123.                         // 设置进度条的最大值  
124.                         pb.setMax(len);  
125.   
126.                         // 2 .假设开启3 个线程  
127.                         **int** threadnumber = 3;  
128.                         **int** blocksize = len / threadnumber;  
129.                         /\*\* 
130.                          \* 线程1 0~ blocksize 线程2 1\*bolocksize ~ 2\*blocksize 线程3 
131.                          \* 2\*blocksize ~ 文件末尾 
132.                          \*/  
133.                         **for** (**int** i = 0; i < threadnumber; i++) \{  
134.                             **int** startposition = i \* blocksize;  
135.                             **int** endpositon = (i + 1) \* blocksize;  
136.                             **if** (i == (threadnumber - 1)) \{  
137.                                 // 最后一个线程  
138.                                 endpositon = len;  
139.                             \}  
140.   
141.                             DownLoadTask task = **new** DownLoadTask(i, path,  
142.                                     startposition, endpositon);  
143.                             task.start();  
144.                         \}  
145.   
146.                     \}  
147.                 \} **catch** (Exception e) \{  
148.                     Toast.makeText(**this**, "下载出现异常", 0).show();  
149.                     e.printStackTrace();  
150.                 \}  
151.               
152.             **break**;  
153.         \}  
154.   
155.     \}  
156.   
157.     **class** DownLoadTask **extends** Thread \{  
158.   
159.         **int** threadid;  
160.         String filepath;  
161.         **int** startposition;  
162.         **int** endpositon;  
163.   
164.         **public** DownLoadTask(**int** threadid, String filepath, **int** startposition,  
165.                 **int** endpositon) \{  
166.             **this**.threadid = threadid;  
167.             **this**.filepath = filepath;  
168.             **this**.startposition = startposition;  
169.             **this**.endpositon = endpositon;  
170.   
171.         \}  
172.   
173.         @Override  
174.         **public** **void** run() \{  
175.             **try** \{  
176.                 File postionfile = **new** File("/mnt/sdcard/" + threadid + ".txt");  
177.                 URL url = **new** URL(filepath);  
178.                 HttpURLConnection conn = (HttpURLConnection) url  
179.                         .openConnection();  
180.                 System.out.println("线程" + threadid + "正在下载 " + "开始位置 : "  
181.                         + startposition + "结束位置 " + endpositon);  
182.   
183.                 **if** (postionfile.exists()) \{  
184.                     FileInputStream fis = **new** FileInputStream(postionfile);  
185.                     **byte**\[\] result = StreamTool.getBytes(fis);  
186.                     String str = **new** String(result);  
187.                     **if** (!"".equals(str)) \{  
188.                         **int** newstartposition = Integer.parseInt(str);  
189.                         **if** (newstartposition > startposition) \{  
190.                             startposition = newstartposition;  
191.                         \}  
192.                     \}  
193.                 \}  
194.   
195.                 // "Range", "bytes=2097152-4194303")  
196.                 conn.setRequestProperty("Range", "bytes=" + startposition + "-"  
197.                         + endpositon);  
198.                 conn.setRequestMethod("GET");  
199.                 conn.setConnectTimeout(5000);  
200.                 conn.setRequestProperty("User-Agent",  
201.                         "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");  
202.                 InputStream is = conn.getInputStream();  
203.                 RandomAccessFile file = **new** RandomAccessFile("/mnt/sdcard/"  
204.                         + getFilenName(filepath), "rwd");  
205.                 // 设置 数据从文件哪个位置开始写  
206.                 file.seek(startposition);  
207.                 **byte**\[\] buffer = **new** **byte**\[1024\];  
208.                 **int** len = 0;  
209.                 // 代表当前读到的服务器数据的位置 ,同时这个值已经存储的文件的位置  
210.                 **int** currentPostion = startposition;  
211.                 // 创建一个文件对象 ,记录当前某个文件的下载位置  
212.   
213.                 **while** ((len = is.read(buffer)) != -1) \{  
214.                     **if** (stopflag) \{  
215.                         **return**;  
216.                     \}  
217.                     file.write(buffer, 0, len);  
218.   
219.                     **synchronized** (MutiledownloadActivity.**this**) \{  
220.                         total += len;  
221.                     \}  
222.   
223.                     currentPostion += len;  
224.                     // 需要把currentPostion 信息给持久化到存储设备  
225.                     String position = currentPostion + "";  
226.                     FileOutputStream fos = **new** FileOutputStream(postionfile);  
227.                     fos.write(position.getBytes());  
228.                     fos.flush();  
229.                     fos.close();  
230.                 \}  
231.   
232.                 file.close();  
233.                 System.out.println("线程" + threadid + "下载完毕");  
234.                 // 当线程下载完毕后 把文件删除掉  
235.                 **if** (postionfile.exists()) \{  
236.                     postionfile.delete();  
237.                 \}  
238.   
239.             \} **catch** (Exception e) \{  
240.                 e.printStackTrace();  
241.             \}  
242.   
243.             **super**.run();  
244.         \}  
245.   
246.     \}  
247.   
248.     **public** String getFilenName(String path) \{  
249.         **int** start = path.lastIndexOf("/") + 1;  
250.         **return** path.substring(start, path.length());  
251.     \}

1.  \}

转载地址http://blog.csdn.net/dacainiao007/article/details/8222779