无法从 ActivityResultContracts.CreateDocument() 的内容 uri 中获取文件类型

Question

I am using ActivityResultLauncher to allow the user to select a file in which I will save a bitmap. I need to get the file extension of the file the user selected so that I can set the Bitmap.CompressFormat when I save the Bitmap. Here is my code:

    private ActivityResultLauncher<String> activityResultLauncher =
                registerForActivityResult(new ActivityResultContracts.CreateDocument(),
                new ActivityResultCallback<Uri>() {
                    @Override
                    public void onActivityResult(Uri uri) {
                        Timber.d("Result = %s", uri.toString());
                        OutputStream outputStream = null;
                        Bitmap bitmap = cameraViewModel.getImage();
                        try {
                            ContentResolver contentResolver = mainActivity.getContentResolver();
                            MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
                            String type = mimeTypeMap.getExtensionFromMimeType(contentResolver.getType(uri));
                            outputStream = contentResolver.openOutputStream(uri);
                            if (outputStream != null && bitmap != null) {
                                bitmap.compress(Bitmap.CompressFormat.PNG, 100, outputStream);
                                outputStream.close();
                            }
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                });

The type is always returned as null, is there anyway to get past the opaqueness of the content uri and see the actual filename

Answer 1

Get rid of MimeTypeMap and call getType() on the ContentResolver .

The type is always returned as null, is there anyway to get past the opaqueness of the content uri and see the actual filename

No, because it is not necessarily a file.