东西拼凑，最终弄出来能够用的代码

[1].[代码] [Java]代码

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public class DownManagerTask {         private static final String TAG = "DownManagerTask" ;         private static DownManagerTask DOWN_TASK = new DownManagerTask();         private Context context;     private DownloadManager downloadManager;     long downloadId = - 1 ;     private Bitmap bitmap;     private ImageView imageView;                 private DownManagerTask(){}         public static DownManagerTask getInstance(){         return DOWN_TASK;     }         @SuppressLint ( "InlinedApi" )     public void init(Context context,ImageView imageView){         this .context = context;         this .imageView = imageView;         downloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);     }         /**      * 将下载的图片转化成bitMap      *      */     @SuppressLint ( "NewApi" )     private void parseBitMap(){         try {             ParcelFileDescriptor pfd = downloadManager.openDownloadedFile(downloadId);             FileDescriptor fileDescriptor = pfd.getFileDescriptor();              bitmap = BitmapFactory.decodeFileDescriptor(fileDescriptor);              pfd.close();         } catch (Exception e){              e.printStackTrace();         }     }         /**      * 下载方法      * @param url      */     @SuppressLint ( "NewApi" )     public void download(String url){         Log.d(TAG, url);         Uri uri = Uri.parse(url);         DownloadManager.Request request = new DownloadManager.Request(uri);         request.setAllowedNetworkTypes(Request.NETWORK_MOBILE                 | Request.NETWORK_WIFI);         request.setAllowedOverRoaming( false );         MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();         String mimeString = mimeTypeMap.getMimeTypeFromExtension(MimeTypeMap                 .getFileExtensionFromUrl(url));         request.setMimeType(mimeString);         //request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "Bugdroid.png");          request.allowScanningByMediaScanner();         request.setVisibleInDownloadsUi( true );         downloadId = downloadManager.enqueue(request);         Log.d(TAG, "downloadId:" +downloadId);         context.registerReceiver(receiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));     }         public void unregisterReceiver(){         context.unregisterReceiver(receiver);     }         @SuppressLint ( "NewApi" )     public void temp(){         Cursor c = downloadManager.query( new DownloadManager.Query().setFilterById(downloadId));         if (c != null ){             c.moveToFirst();             Log.d(TAG,(c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME))));             c.close();         }     }         private BroadcastReceiver receiver = new BroadcastReceiver() {                 @SuppressLint ( "NewApi" )         @Override         public void onReceive(Context context, Intent intent) {             //这里能够取得下载的id，这样就能够知道哪个文件下载完毕了。适用与多个下载任务的监听             if (intent.getAction().equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)){                 Log.v(TAG, "" +intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0 ));                  Log.v(TAG, "download complete" );                  parseBitMap();                  imageView.setImageBitmap(bitmap);                  Toast.makeText(context, "download complete" , Toast.LENGTH_SHORT).show();             }         }     };