Before a client app tries to work with a file for which it has a content URI, the app can request information about the file from the server app, including the file's data type and file size. The data type helps the client app to determine if it can handle the file, and the file size helps the client app set up buffering and caching for the file.
This lesson demonstrates how to query the server app's
FileProvider to retrieve a file's MIME type and size.
Retrieve a file's MIME type
A file's data type indicates to the client app how it should handle the file's contents. To get
the data type of a shared file given its content URI, the client app calls
ContentResolver.getType(). This method returns
the file's MIME type. By default, a
FileProvider determines the file's MIME type from its
The following code snippet demonstrates how a client app retrieves the MIME type of a file once the server app has returned the content URI to the client:
... /* * Get the file's content URI from the incoming Intent, then * get the file's MIME type */ Uri returnUri = returnIntent.getData(); String mimeType = getContentResolver().getType(returnUri); ...
Retrieve a file's name and size
FileProvider class has a default implementation of the
query() method that returns the
name and size of the file associated with a content URI in a
Cursor. The default implementation returns two columns:
The file's name, as a
String. This value is the same as the value returned by
The size of the file in bytes, as a
longThis value is the same as the value returned by
The client app can get both the
SIZE for a file by setting all
of the arguments of
null except for the content URI. For example, this code snippet retrieves a file's
SIZE and displays each one in separate
... /* * Get the file's content URI from the incoming Intent, * then query the server app to get the file's display name * and size. */ Uri returnUri = returnIntent.getData(); Cursor returnCursor = getContentResolver().query(returnUri, null, null, null, null); /* * Get the column indexes of the data in the Cursor, * move to the first row in the Cursor, get the data, * and display it. */ int nameIndex = returnCursor.getColumnIndex(OpenableColumns.DISPLAY_NAME); int sizeIndex = returnCursor.getColumnIndex(OpenableColumns.SIZE); returnCursor.moveToFirst(); TextView nameView = (TextView) findViewById(R.id.filename_text); TextView sizeView = (TextView) findViewById(R.id.filesize_text); nameView.setText(returnCursor.getString(nameIndex)); sizeView.setText(Long.toString(returnCursor.getLong(sizeIndex))); ...
For additional related information, refer to: