Android 多線程下載

1. package my.Thread;
3. import java.io.BufferedInputStream;
4. import java.io.RandomAccessFile;
5. import java.net.HttpURLConnection;
6. import java.net.URL;
7. import java.net.URLConnection;
8. import java.util.concurrent.CountDownLatch;
11. import Android.app.Activity;
12. import android.os.Bundle;
13. import android.os.Environment;
14. import android.view.View;
15. import android.view.View.OnClickListener;
16. import android.widget.Button;
17. import android.widget.TextView;
19. public class ManyThreadActivity extends Activity {
20. /** Called when the activity is first created. */
21. private Button button;
22. private TextView textView;
23. private static final int THREAD_COUNT = 4;
24. private CountDownLatch latch = new CountDownLatch(THREAD_COUNT);
25. private long completeLength = 0;
26. private long fileLength;
27. public static String SaveFile=Environment.getExternalStorageDirectory()+"/DownFile/"+"test.Mp3";
28. public static final String url="http://210.30.12.33:8080/mp3/Beyond.mp3";
29. @Override
30. public void onCreate(Bundle savedInstanceState) {
31. super.onCreate(savedInstanceState);
32. setContentView(R.layout.main);
33. button=(Button)findViewById(R.id.button1);
34. textView=(TextView) findViewById(R.id.editText1);
35. textView.setText(url);
36. button.setOnClickListener(new MyListener());
37. }
38. class MyListener implements OnClickListener{
40. @Override
41. public void onClick(View v) {
42. // TODO Auto-generated method stub
43. try {
44. download(url);
45. } catch (Exception e) {
46. // TODO Auto-generated catch block
47. e.printStackTrace();
48. }
49. }
51. }
53. //進行下載的線程
54. class DownloadThread extends Thread {
55. private URL url;
56. private RandomAccessFile file;
57. private long from;
58. private long end;
60. /**
61. * @param url 下載的URL
62. * @param file 下載完成之後存儲的文件
63. * @param from 當前線程對應文件的起始位置
64. * @param end 當前線程對應文件的結束位置
65. */
66. DownloadThread(URL url, RandomAccessFile file, long from, long end) {
67. this.url = url;
68. this.file = file;
69. this.from = from;
70. this.end = end;
71. }
73. public void run() {
74. try {
75. long pos = from;
76. byte[] buf = new byte[1024*8];
78. HttpURLConnection cn = (HttpURLConnection) url.openConnection();
80. //設置請求的起始和結束位置。
81. cn.setRequestProperty("Range", "bytes=" + from + "-" + end);
83. BufferedInputStream bis = new BufferedInputStream(cn.getInputStream());
84. int len;
85. while ((len = bis.read(buf)) > 0) {
86. synchronized (file) {
87. file.seek(pos);
88. file.write(buf, 0, len);
89. }
90. pos += len;
91. completeLength += len;
92. System.out.println(completeLength * 100 / fileLength + "%");
93. }
94. cn.disconnect();
95. } catch (Exception e) {
96. e.printStackTrace();
97. }
98. latch.countDown();
99. }
100. }
102. public void download(String address) throws Exception {
103. URL url = new URL(address);
104. URLConnection cn = url.openConnection();
105. fileLength = cn.getContentLength();
106. long packageLength = fileLength / THREAD_COUNT;//每個線程要下載的字節數
107. long leftLength = fileLength % THREAD_COUNT;//剩下的字節數
109. RandomAccessFile file = new RandomAccessFile(SaveFile, "rw");
111. System.out.println(fileLength);
112. //計算每個線程請求的起始位置和結束位置。
113. /*
114. * 第一個線程的起始位置是0~0+packageLength(每個線程要下載的字節數)
115. * 第二個線程的起始位置是endPos+1(第一個線程的packageLength+1)~endPos+1+packageLength
116. * 第二個線程的起始位置是.........
117. */
118. long pos = 0;
119. for (int i = 0; i < THREAD_COUNT; i++) {
120. long endPos = pos + packageLength;
121. new DownloadThread(url, file, pos, endPos).start();
122. if(leftLength > 0) {
123. endPos++;
124. leftLength--;
125. }
126. pos = endPos;
127. }
128. latch.await();
129. }
131. }

保存為test.mp3文件