Android providers downloads documents document 192

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Luvnish Monga Luvnish Monga 5, 2 2 gold badges 21 21 silver badges 27 27 bronze badges. Sachidanand Navik Sachidanand Navik 1. Don't forgot to give permissions else probability of down vote increases for my post — Sachidanand Navik. Following are fixes i found first add these two lines in your AndroidManifest file Than add the below line just after setContentView method ActivityCompat.

Waseem Khan Waseem Khan 50 6 6 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. The next step in writing a custom document provider is to subclass the abstract class DocumentsProvider. At minimum, you must implement the following methods:.

These are the only methods you are strictly required to implement, but there are many more you might want to. See DocumentsProvider for details. Your implementation of queryRoots needs to return a Cursor pointing to all the root directories of your document provider, using columns defined in DocumentsContract.

In the following snippet, the projection parameter represents the specific fields the caller wants to get back. The snippet creates a new cursor and adds one row to it—one root, a top level directory, like Downloads or Images. Most providers only have one root. You might have more than one, for example, in the case of multiple user accounts.

In that case, just add a second row to the cursor. If your document provider connects to a dynamic set of roots—for example, to a USB device that might be disconnected or an account that the user can sign out from—you can update the document UI to stay in sync with those changes using the ContentResolver.

Your implementation of queryChildDocuments must return a Cursor that points to all the files in the specified directory, using columns defined in DocumentsContract. This method gets called when the user chooses your root in the picker UI. The system then calls this method any time the user selects a subdirectory within your documents provider.

This snippet makes a new cursor with the requested columns, then adds information about every immediate child in the parent directory to the cursor.

A child can be an image, another directory—any file:. Your implementation of queryDocument must return a Cursor that points to the specified file, using columns defined in DocumentsContract. The queryDocument method returns the same information that was passed in queryChildDocuments , but for a specific file:. Your document provider can also provide thumbnails for a document by overriding the DocumentsProvider.

The following code snippet provides an example of how to implement the DocumentsProvider. Caution : A document provider should not return thumbnail images more than double the size specified by the sizeHint parameter. You must implement openDocument to return a ParcelFileDescriptor representing the specified file.

Other apps can use the returned ParcelFileDescriptor to stream data. The system calls this method after the user selects a file, and the client app requests access to it by calling openFileDescriptor. For example:. If your document provider streams files or handles complicated data structures, consider implementing the createReliablePipe or createReliableSocketPair methods.

Those methods allow you to create a pair of ParcelFileDescriptor objects, where you can return one and send the other via an ParcelFileDescriptor. You can get the complete code for the snippet above by downloading the StorageProvider code sample. You can allow client apps to create files within your document provider. Your document provider also needs to implement the createDocument method. When a user selects a directory within your document provider to save a new file, the document provider receives a call to createDocument.

The client app can then use that ID to get a handle for the file and, ultimately, call openDocument to write to the new file. The following code snippet demonstrates how to create a new file within a document provider. In addition to opening, creating, and viewing files, your document provider can also allow client apps the ability to rename, copy, move, and delete files.

You also need to implement the corresponding method of the DocumentsProvider class. Virtual files , a feature introduced in Android 7. To enable other apps to view virtual files, your document provider needs to produce an alternative openable file representation for the virtual files.

For example, imagine a document provider contains a file format that other apps cannot directly open, essentially a virtual file. The document provider then returns the virtual file in a different, but openable, file format like an image. The client app can then open the virtual file for the user to view.

This flag alerts client apps that the file does not have a direct bytecode representation and cannot be directly opened. If you declare that a file in your document provider is virtual, it is strongly recommended that you make it available in another MIME type like an image or a PDF.

The document provider declares the alternate MIME types that it supports for viewing a virtual file by overriding the getDocumentStreamTypes method. When client apps call the getStreamTypes android. Uri, java. String method, the system calls the getDocumentStreamTypes method of the document provider.

After the client determines that the document provider can produce the document in a viewable file format, the client app calls the openTypedAssetFileDescriptor method, which internally calls the document provider's openTypedDocument method.

The document provider returns the file to the client app in the requested file format. The following code snippet demonstrates a simple implementation of the getDocumentStreamTypes and openTypedDocument methods. Suppose your document provider is a password-protected cloud storage service and you want to make sure that users are logged in before you start sharing their files. What should your app do if the user is not logged in? A content provider can be used to manage access to a variety of data storage sources, including both structured data, such as a SQLite relational database, or unstructured data such as image files.

For more information on the types of storage available on Android, see Storage options , as well as Designing data storage. Content providers offer granular control over the permissions for accessing data.

You can choose to restrict access to a content provider from solely within your application, grant blanket permission to access data from other applications, or configure different permissions for reading and writing data. For more information on using content providers securely, see Security tips for storing data , as well as Content provider permissions. You can use a content provider to abstract away the details for accessing different data sources in your application. For example, your application might store structured records in a SQLite database, as well as video and audio files.

You can use a content provider to access all of this data, if you implement this development pattern in your application. Also note that CursorLoader objects rely on content providers to run asynchronous queries and then return the results to the UI layer in your application. For more information on using a CursorLoader to load data in the background, see Running a query with a CursorLoader.

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