如何在Android Q中从contentResolver.openFileDescriptor(Uri uri, String s)获取媒体项real_Path？

Question

MediaStore.MediaColumns.DATA 常量在 API 级别 Q 中已弃用。

应用程序可能没有文件系统权限来直接访问此路径。应用程序不应尝试直接打开此路径，而应使用 ContentResolver#openFileDescriptor(Uri, String) 来获取访问权限。对于面向 Build.VERSION_CODES.Q 或更高版本的应用程序，此值将始终为 NULL。

Answer 1

确实如此，我们无法获得真正的路径。只是简单的方法使用 contentResolver() 打开流并将文件的全部内容复制到新文件中，为了获取文件信息，我们需要调用 getContentResolver().query() 的 query() 方法，然后我们可以获得文件的 DISPLAY_NAME以及更多信息，例如 FILE_SIZE。

对于那些赞成该问题的人来说，简单的代码示例：

public class MainFragment extends Fragment {

    private Button openGallery;
    private File selectedFile;
    private Context context;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        context = container.getContext();
        return inflater.inflate(R.layout.fragment_question, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        openGallery = view.findViewById(R.id.openGallery);
        openGallery.setOnClickListener(v->browseFile());
    }


    private void browseFile() {

        if (ActivityCompat.checkSelfPermission(context, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
            openFiles();
        } else {
            requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 786);
        }
    }

    private void openFiles() {

        deleteFileFromCacheDir();

        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.setType("*/*");
        intent.addCategory(Intent.CATEGORY_OPENABLE);

        if (intent.resolveActivity(context.getPackageManager()) != null) {
            startActivityForResult(intent, 786);
        }
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == 786 && resultCode == -1 && data != null) {

            Uri uri = data.getData();
            openStreamAndCopyContent(uri); // Here i am just copy the content of file and paste it into my new file. You can check the type of the file image/video/audio & do it whatever you want

            // Now here is your file

            if (selectedFile != null && selectedFile.exists()){
                // Do it whatever you want Or send it to server 
            } 

        }

    }

    private void openStreamAndCopyContent(Uri uri) {

        try {

            String fileName = "temp" + System.currentTimeMillis() + "." + MimeTypeMap.getSingleton().getExtensionFromMimeType(context.getContentResolver().getType(uri));
            selectedFile = new File(context.getCacheDir().getAbsolutePath() + File.separator + fileName);

            InputStream inputStream = context.getContentResolver().openInputStream(uri);

            if (inputStream != null) {
                Utility.copy(inputStream, selectedFile);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == 786) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                openFiles();
            } else if (grantResults[0] == PackageManager.PERMISSION_DENIED && getActivity() != null) {

                if (!ActivityCompat.shouldShowRequestPermissionRationale(getActivity(), Manifest.permission.READ_EXTERNAL_STORAGE)) {

                    new AlertDialog.Builder(context).setTitle(R.string.permission_required).setMessage(R.string.permission_message)
                            .setPositiveButton(R.string.open_settings, (dialog, which) ->
                                    context.startActivity(new Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS,
                                            Uri.parse("package:" + BuildConfig.APPLICATION_ID)))).setNegativeButton(R.string.close, null).show();
                }
            }
        }
    }


    private void deleteFileFromCacheDir() {

        if (selectedFile != null && selectedFile.exists()) {
            if (selectedFile.delete()) {
                selectedFile = null;
            }
        }
    }

    @Override
    public void onDestroyView() {

        deleteFileFromCacheDir();

        super.onDestroyView();
    }



    }

Answer 2

我相信这是不可能的，因为从编程的角度来看你根本不需要这条路径。

您无法读取/更改/删除真实路径的文件。您应该使用 ContentResolver 来执行问题中所述的这些操作。

如果您只想向用户显示路径，那么我建议提供一个选项来使用 Intent.createChooser 打开/共享文件，或者仅显示 MediaColumns.RELATIVE_PATH。

Answer 3

就我而言，我使用了 cacheDir

val fileDescriptorPath = fileDescriptor(myUri)
//use path and then delete it
fileDescriptorPath?.delete()

private fun fileDescriptor(uri: Uri?): File? {
    if (uri == null) return null
    var input: FileInputStream? = null
    var output: FileOutputStream? = null
    val filePath: String = File(context.cacheDir, "tmp.fileExtension").absolutePath
   return try {
       val parcelFileDescriptor: ParcelFileDescriptor = context.contentResolver.openFileDescriptor(uri, "r")!!
       val fileDescriptor = parcelFileDescriptor.fileDescriptor
        input = FileInputStream(fileDescriptor)
        output = FileOutputStream(filePath)
        var read: Int
        val bytes = ByteArray(1024)
        while (input.read(bytes).also { read = it } != -1) {
            output.write(bytes, 0, read)
        }
        parcelFileDescriptor.close()
        File(filePath)
    } catch (ignored: IOException) {
        Log.v("pathFileDescriptor", "IOException: ${ignored.message}")
       null
    } finally {
        input?.close()
        output?.close()
    }
}