原始完成于：2014-10-24 20:01:03
DownloadManager是一个处理HTTP下载请求的系统服务：
1. 基本用法
1 private void download() {
2 Request request = new Request(Uri.parse("http://files.cnblogs.com/wlrhnh/JeejenKnowledge-15793-release.apk"));
3 request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "4444.zip");
4 request.setNotificationVisibility(Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
5 long id = mDownloadMgr.enqueue(request);
6 Log.d("MMLL", "下载 id = " + id);
7 }
绿色代码指定文件下载路径，如果不指定，那么默认下载在“/data/data/com.android.providers.downloads/cache/***.apk”。代码中的id是个非常重要的属性，它表示DownloadManager给这次下载指定的ID，同时也是该文件在数据库中的column_id。默认行为，下载完成后Notification会自动消失；
红色代码表示下载完成后，Notification仍旧显示在下拉列表中，该API只能在API 11之后调用。
2. 获取下载文件的信息
API 11中新增了一个API，可以直接去到下载文件的Uri，如下：
1 Uri uri = mDownloadMgr.getUriForDownloadedFile(_id);
2 uri = file:///storage/emulated/0/Download/4444-4.zip //指定路径
3 uri = content://downloads/my_downloads/118 //默认路径
代码中红色log指的分别是指定路径和默认路径下得到的Uri，但是在API 低于11的系统中怎么使用呢？
DownloadManager提供了Query接口，代码如下：
1 int _id = -1;
2 String local_filename = null;
3 String local_uri = null;
4 Query query = new Query();
5 Cursor cursor = mDownloadMgr.query(query);
6 if (cursor != null) {
7 cursor.moveToFirst();
8 _id = cursor.getInt(cursor.getColumnIndex("_id"));
9 local_filename = cursor.getString(cursor.getColumnIndex("local_filename"));
10 local_uri = cursor.getString(cursor.getColumnIndex("local_uri"));
11 }
上面代码中得到的Cursor的数量为1，且就是自己应用程序中调用DownloadManager下载的最新一次文件信息， 可以看到query既没有设置Uri，也没有指定_id,那怎么返回这唯一的一条信息呢？其实在生成query时有一些默认值，其中Uri如下：
1 /**
2 * The content:// URI to access downloads owned by the caller's UID.
3 */
4 public static final Uri CONTENT_URI = Uri.parse("content://downloads/my_downloads");
而且秘密就在注释中，查询时会更据caller的UID，所以才会返回自己下载的文件的信息；
cursor的全部Column如下：
1 D/MMLL (16614): column = _id
2 D/MMLL (16614): column = local_filename
3 D/MMLL (16614): column = mediaprovider_uri
4 D/MMLL (16614): column = destination
5 D/MMLL (16614): column = title
6 D/MMLL (16614): column = description
7 D/MMLL (16614): column = uri
8 D/MMLL (16614): column = status
9 D/MMLL (16614): column = hint
10 D/MMLL (16614): column = media_type
11 D/MMLL (16614): column = total_size
12 D/MMLL (16614): column = last_modified_timestamp
13 D/MMLL (16614): column = bytes_so_far
14 D/MMLL (16614): column = local_uri
15 D/MMLL (16614): column = reason
16 D/MMLL (16614): column = bypass_recommended_size_limit
17 D/MMLL (16614): column = allowed_network_types
18 D/MMLL (16614): column = entity
对应的值如下：
1 D/MMLL (22053): cursor.getString(0) = 107
2 D/MMLL (22053): cursor.getString(0) = /data/data/com.android.providers.downloads/cache/4_lauchmode.zip
3 D/MMLL (22053): cursor.getString(0) = null
4 D/MMLL (22053): cursor.getString(0) = 2
5 D/MMLL (22053): cursor.getString(0) = 4_lauchmode.zip
6 D/MMLL (22053): cursor.getString(0) =
7 D/MMLL (22053): cursor.getString(0) = http://files.cnblogs.com/wlrhnh/4_lauchmode.zip
8 D/MMLL (22053): cursor.getString(0) = 200
9 D/MMLL (22053): cursor.getString(0) = null
10 D/MMLL (22053): cursor.getString(0) = application/zip
11 D/MMLL (22053): cursor.getString(0) = 1315681
12 D/MMLL (22053): cursor.getString(0) = 1414137592255
13 D/MMLL (22053): cursor.getString(0) = 1315681
14 D/MMLL (22053): cursor.getString(0) = content://downloads/my_downloads/107
15 D/MMLL (22053): cursor.getString(0) = placeholder
16 D/MMLL (22053): cursor.getString(0) = 0
17 D/MMLL (22053): cursor.getString(0) = -1
18 D/MMLL (22053): cursor.getString(0) = null
或者
1 D/MMLL ( 8796): cursor.getString(0) = 113
2 D/MMLL ( 8796): cursor.getString(0) = /storage/emulated/0/Download/4444.zip
3 D/MMLL ( 8796): cursor.getString(0) = content://media/external/file/34731
4 D/MMLL ( 8796): cursor.getString(0) = 4
5 D/MMLL ( 8796): cursor.getString(0) = 4444.zip
6 D/MMLL ( 8796): cursor.getString(0) =
7 D/MMLL ( 8796): cursor.getString(0) = http://files.cnblogs.com/wlrhnh/4_lauchmode.zip
8 D/MMLL ( 8796): cursor.getString(0) = 200
9 D/MMLL ( 8796): cursor.getString(0) = file:///storage/emulated/0/Download/4444.zip
10 D/MMLL ( 8796): cursor.getString(0) = application/zip
11 D/MMLL ( 8796): cursor.getString(0) = 1315681
12 D/MMLL ( 8796): cursor.getString(0) = 1414149416875
13 D/MMLL ( 8796): cursor.getString(0) = 1315681
14 D/MMLL ( 8796): cursor.getString(0) = file:///storage/emulated/0/Download/4444.zip
15 D/MMLL ( 8796): cursor.getString(0) = placeholder
16 D/MMLL ( 8796): cursor.getString(0) = 0
17 D/MMLL ( 8796): cursor.getString(0) = -1
18 D/MMLL ( 8796): cursor.getString(0) = null
3. 监听下载状态的BroadCast，代码如下：
1 private void regisiterBroadCast() {
2 IntentFilter intentFilter = new IntentFilter();
3 intentFilter.addAction(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
4 intentFilter.addAction(DownloadManager.ACTION_NOTIFICATION_CLICKED);
5 intentFilter.addAction(DownloadManager.ACTION_VIEW_DOWNLOADS);
6
7 this.registerReceiver(new BroadcastReceiver() {
8 @Override
9 public void onReceive(Context context, Intent intent) {
10 if (intent != null) {
11 Log.d("MMLL", "intent.getAction = " + intent.getAction());
12 Bundle bundle = intent.getExtras();
13 if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(intent.getAction())) {
14 Log.d("MMLL", "ACTION_DOWNLOAD_COMPLETE");
15 } else if (DownloadManager.ACTION_NOTIFICATION_CLICKED.equals(intent.getAction())) {
16 Log.d("MMLL", "ACTION_NOTIFICATION_CLICKED");
17 } else if (DownloadManager.ACTION_VIEW_DOWNLOADS.equals(intent.getAction())) {
18 Log.d("MMLL", "ACTION_VIEW_DOWNLOADS");
19 }
20 }
21 }
22 }, intentFilter);
23 }
除了下载完成后发送的广播能接受到之外，其他的两个广播暂时还收不到，待研究；
4. 如果下载的是APK，并且药调用Installer来安装，安装的代码如下：
1 private void installApk(Uri uri) {
2 Intent intent = new Intent(Intent.ACTION_VIEW);
3 intent.setDataAndType(uri, "application/vnd.android.package-archive");
4 startActivity(intent);
5 }
可见需要传入一个Uri，在前面的分析中，我们知道设置下载路径和默认下载路径返回的Uri是不一样的，
1 uri = file:///storage/emulated/0/Download/4444-4.zip //指定路径
2 uri = content://downloads/my_downloads/118 //默认路径
此时第一个uri传进去是可以正常安装的，但是第二个uri则不行，会提示“包解析失败”神马的，因此，如果下载的是APK，那么最好还是指定一下下载路径；
5. 那么在API 11之前如何获取Uri呢？
有两种方式：
1>. 前面提到的查询数据库，字段是local_uri
2>. 有一种比较复杂的方式，仅供参考：
1 public Uri getDownloadFile() {
2 long downloadId = getDownloadId();
3 int status = queryDownloadStatus(downloadId);
4 if (DownloadManager.STATUS_SUCCESSFUL == status) {
5 if (Build.VERSION.SDK_INT >= 11) {
6 return mDownloadMgr.getUriForDownloadedFile(downloadId);
7 } else {
8 FileOutputStream outStream = null;
9 ParcelFileDescriptor.AutoCloseInputStream instream = null;
10 try {
11 ParcelFileDescriptor desc = mDownloadMgr.openDownloadedFile(downloadId);
12 instream = new ParcelFileDescriptor.AutoCloseInputStream(desc);
13
14 String fileName = Environment.getExternalStorageDirectory().getAbsolutePath().toString();
15 fileName += "/jeejen/" + Calendar.getInstance().getTimeInMillis() + "_" + downloadId + ".apk";
16 File file = new File(fileName);
17 if (!file.getParentFile().exists()) {
18 file.getParentFile().mkdirs();
19 }
20 file.createNewFile();
21 outStream = new FileOutputStream(file);
22 byte[] buffer = new byte[1024];
23 int read;
24
25 while ((read = instream.read(buffer)) != -1) {
26 outStream.write(buffer, 0, read);
27 }
28
29 return Uri.fromFile(file);
30 } catch (Exception e) {
31 e.printStackTrace();
32 return null;
33 } finally {
34 try {
35 if (outStream != null) {
36 outStream.close();
37 }
38 } catch (Exception e) {
39 }
40 try {
41 if (instream != null) {
42 instream.close();
43 }
44 } catch (Exception e) {
45 }
46 }
47 }
48 }
49 return null;
50 }
个人觉得这种方式比较复杂，但不失为一种思路。比较简单粗暴的方式是：
1 private void copyToSD(String path) {
2 FileInputStream inputStream = null;
3 FileOutputStream outputStream = null;
4 try {
5 inputStream = new FileInputStream(path);
6 outputStream = new FileOutputStream("sdcard/jeejen/大卫.zip");
7 byte[] bb = new byte[1024];
8 int count = -1;
9 while ((count = inputStream.read(bb)) != -1) {
10 outputStream.write(bb, 0, count);
11 }
12 outputStream.flush();
13 } catch (FileNotFoundException e) {
14 e.printStackTrace();
15 } catch (IOException e) {
16 e.printStackTrace();
17 } finally {
18 if (inputStream != null) {
19 try {
20 inputStream.close();
21 } catch (IOException e) {
22 e.printStackTrace();
23 }
24 }
25 if (outputStream != null) {
26 try {
27 outputStream.close();
28 } catch (IOException e) {
29 e.printStackTrace();
30 }
31 }
32 }
33 }
把local_filename字段对应的值传进去即可；
6. 如何获取当前下载进度？
获取进度的基本原理是注册一个ContentObserver，因为伴随着下载，会往数据库中写入下载文件的大小和当前下载完成的大小。代码如下：
1 private void getProgress(long id) {
2 long total_size = -1L;
3 long bytes_so_far = -1L;
4 Query query = new Query().setFilterById(id);
5 Cursor cur = mDownloadMgr.query(query);
6 if (cur != null && cur.moveToFirst()) {
7 do {
8 total_size = cur.getLong(cur.getColumnIndex("total_size"));
9 bytes_so_far = cur.getLong(cur.getColumnIndex("bytes_so_far"));
10 Log.d("MMLL", "bytes_so_far = " + bytes_so_far + ", total_size = " + total_size);
11 } while (cur.moveToNext());
12 }
13 }
14
15 private class DownloadChangeObserver extends ContentObserver {
16
17 public DownloadChangeObserver(Handler handler) {
18 super(handler);
19 }
20
21 @Override
22 public void onChange(boolean selfChange) {
23 super.onChange(selfChange);
24 getProgress(id);
25 }
26
27 /*@Override
28 public void onChange(boolean selfChange, Uri uri) {
29 super.onChange(selfChange, uri);
30 }*/
31
32 }
然后注册，如下：
1 getContentResolver().registerContentObserver(Uri.parse("content://downloads/my_downloads"), true, new DownloadChangeObserver(null));
OK，至此Over