使用Android自带DownloadManager下载文件

SDK在API Level 9中加入了DownloadManager服务，可以将长时间的下载任务交给系统，完全由系统管理。

直接看实例代码：

[java] view plain copy

1. packagecom.hebaijun.downloadtest;
3. importjava.io.UnsupportedEncodingException;
4. importjava.net.URLEncoder;
6. importandroid.app.Activity;
7. importandroid.app.DownloadManager;
8. importandroid.app.DownloadManager.Request;
9. importandroid.content.BroadcastReceiver;
10. importandroid.content.Context;
11. importandroid.content.Intent;
12. importandroid.content.IntentFilter;
13. importandroid.content.SharedPreferences;
14. importandroid.database.Cursor;
15. importandroid.net.Uri;
16. importandroid.os.Bundle;
17. importandroid.preference.PreferenceManager;
18. importandroid.util.Log;
19. importandroid.webkit.MimeTypeMap;
21. publicclassDownloadTestActivityextendsActivity{
22. privateDownloadManagerdownloadManager;
23. privateSharedPreferencesprefs;
24. privatestaticfinalStringDL_ID="downloadId";
25. /**Calledwhentheactivityisfirstcreated.*/
26. @Override
27. publicvoidonCreate(BundlesavedInstanceState){
28. super.onCreate(savedInstanceState);
29. setContentView(R.layout.main);
30. downloadManager=(DownloadManager)getSystemService(DOWNLOAD_SERVICE);
31. prefs=PreferenceManager.getDefaultSharedPreferences(this);
32. }
33. @Override
34. protectedvoidonPause(){
35. //TODOAuto-generatedmethodstub
36. super.onPause();
37. unregisterReceiver(receiver);
38. }
39. @Override
40. protectedvoidonResume(){
41. //TODOAuto-generatedmethodstub
42. super.onResume();
43. if(!prefs.contains(DL_ID)){
44. Stringurl="http://10.0.2.2/android/film/G3.mp4";
45. //开始下载
46. Uriresource=Uri.parse(encodeGB(url));
47. DownloadManager.Requestrequest=newDownloadManager.Request(resource);
48. request.setAllowedNetworkTypes(Request.NETWORK_MOBILE|Request.NETWORK_WIFI);
49. request.setAllowedOverRoaming(false);
50. //设置文件类型
51. MimeTypeMapmimeTypeMap=MimeTypeMap.getSingleton();
52. StringmimeString=mimeTypeMap.getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(url));
53. request.setMimeType(mimeString);
54. //在通知栏中显示
55. request.setShowRunningNotification(true);
56. request.setVisibleInDownloadsUi(true);
57. //sdcard的目录下的download文件夹
58. request.setDestinationInExternalPublicDir("/download/","G3.mp4");
59. request.setTitle("移动G3广告");
60. longid=downloadManager.enqueue(request);
61. //保存id
62. prefs.edit().putLong(DL_ID,id).commit();
63. }else{
64. //下载已经开始，检查状态
65. queryDownloadStatus();
66. }
68. registerReceiver(receiver,newIntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
69. }
71. /**
72. *如果服务器不支持中文路径的情况下需要转换url的编码。
73. *@paramstring
74. *@return
75. */
76. publicStringencodeGB(Stringstring)
77. {
78. //转换中文编码
79. Stringsplit[]=string.split("/");
80. for(inti=1;i<split.length;i++){
81. try{
82. split[i]=URLEncoder.encode(split[i],"GB2312");
83. }catch(UnsupportedEncodingExceptione){
84. e.printStackTrace();
85. }
86. split[0]=split[0]+"/"+split[i];
87. }
88. split[0]=split[0].replaceAll("\\+","%20");//处理空格
89. returnsplit[0];
90. }
92. privateBroadcastReceiverreceiver=newBroadcastReceiver(){
93. @Override
94. publicvoidonReceive(Contextcontext,Intentintent){
95. //这里可以取得下载的id，这样就可以知道哪个文件下载完成了。适用与多个下载任务的监听
96. Log.v("intent",""+intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID,0));
97. queryDownloadStatus();
98. }
99. };
101. privatevoidqueryDownloadStatus(){
102. DownloadManager.Queryquery=newDownloadManager.Query();
103. query.setFilterById(prefs.getLong(DL_ID,0));
104. Cursorc=downloadManager.query(query);
105. if(c.moveToFirst()){
106. intstatus=c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
107. switch(status){
108. caseDownloadManager.STATUS_PAUSED:
109. Log.v("down","STATUS_PAUSED");
110. caseDownloadManager.STATUS_PENDING:
111. Log.v("down","STATUS_PENDING");
112. caseDownloadManager.STATUS_RUNNING:
113. //正在下载，不做任何事情
114. Log.v("down","STATUS_RUNNING");
115. break;
116. caseDownloadManager.STATUS_SUCCESSFUL:
117. //完成
118. Log.v("down","下载完成");
119. break;
120. caseDownloadManager.STATUS_FAILED:
121. //清除已下载的内容，重新下载
122. Log.v("down","STATUS_FAILED");
123. downloadManager.remove(prefs.getLong(DL_ID,0));
124. prefs.edit().clear().commit();
125. break;
126. }
127. }
128. }
129. }

最后需要的权限是：

<uses-permission android:name="android.permission.INTERNET"/>

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

如果需要隐藏下载工具的提示和显示，修改代码：

request.setShowRunningNotification(false);

request.setVisibleInDownloadsUi(false);

加入下面的权限：

<uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION"/>

http://blog.youkuaiyun.com/lixiang0522/article/details/7608310