既然上面的答案对我不起作用，下面是对我有效的解决方案:

对于>19和<=19 API级别。

这个方法涵盖了从uri中获取filePath的所有情况

/**
 * Get a file path from a Uri. This will get the the path for Storage Access
 * Framework Documents, as well as the _data field for the MediaStore and
 * other file-based ContentProviders.
 *
 * @param context The activity.
 * @param uri The Uri to query.
 * @author paulburke
 */
public static String getPath(final Context context, final Uri uri) {

    // DocumentProvider
    if ( Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT && DocumentsContract.isDocumentUri(context, uri)) {
        // ExternalStorageProvider
        if (isExternalStorageDocument(uri)) {
            final String docId = DocumentsContract.getDocumentId(uri);
            final String[] split = docId.split(":");
            final String type = split[0];

            if ("primary".equalsIgnoreCase(type)) {
                return Environment.getExternalStorageDirectory() + "/" + split[1];
            }else{
                Toast.makeText(context, "Could not get file path. Please try again", Toast.LENGTH_SHORT).show();
            }
        }
        // DownloadsProvider
        else if (isDownloadsDocument(uri)) {

            final String id = DocumentsContract.getDocumentId(uri);
            final Uri contentUri = ContentUris.withAppendedId(
                    Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));

            return getDataColumn(context, contentUri, null, null);
        }
        // MediaProvider
        else if (isMediaDocument(uri)) {
            final String docId = DocumentsContract.getDocumentId(uri);
            final String[] split = docId.split(":");
            final String type = split[0];

            Uri contentUri = null;
            if ("image".equals(type)) {
                contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
            } else if ("video".equals(type)) {
                contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
            } else if ("audio".equals(type)) {
                contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            } else {
                contentUri = MediaStore.Files.getContentUri("external");
            }

            final String selection = "_id=?";
            final String[] selectionArgs = new String[] {
                    split[1]
            };

            return getDataColumn(context, contentUri, selection, selectionArgs);
        }
    }
    // MediaStore (and general)
    else if ("content".equalsIgnoreCase(uri.getScheme())) {
        return getDataColumn(context, uri, null, null);
    }
    // File
    else if ("file".equalsIgnoreCase(uri.getScheme())) {
        return uri.getPath();
    }

    return null;
}

下面API 19使用这段代码从URI中获取文件路径:

public String getRealPathFromURI(Context context, Uri contentUri) {
  Cursor cursor = null;
  try { 
    String[] proj = { MediaStore.Images.Media.DATA };
    cursor = context.getContentResolver().query(contentUri,  proj, null, null, null);
    int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
    cursor.moveToFirst();
    return cursor.getString(column_index);
  } finally {
    if (cursor != null) {
      cursor.close();
    }
  }
}

我用一行代码做到这一点:

val bitmap = MediaStore.Images.Media。getBitmap (contentResolver uri)

在onActivityResult中看起来是这样的:

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    if (resultCode == Activity.RESULT_OK && requestCode == REQUEST_CODE_IMAGE_PICKER ) {
        data?.data?.let { imgUri: Uri ->
            val bitmap = MediaStore.Images.Media.getBitmap(contentResolver, imgUri)
        }
    }
}

这个解决方案适用于所有情况:

在某些情况下，从URL中获取路径太难了。那你为什么需要路径?把文件复制到其他地方?你不需要路径。

public void SavePhotoUri (Uri imageuri, String Filename){

    File FilePath = context.getDir(Environment.DIRECTORY_PICTURES,Context.MODE_PRIVATE);
    try {
        Bitmap selectedImage = MediaStore.Images.Media.getBitmap(context.getContentResolver(), imageuri);
        String destinationImagePath = FilePath + "/" + Filename;
        FileOutputStream destination = new FileOutputStream(destinationImagePath);
        selectedImage.compress(Bitmap.CompressFormat.JPEG, 100, destination);
        destination.close();
    }
    catch (Exception e) {
        Log.e("error", e.toString());
    }
}

不要尝试在文件系统中查找uri，那样在数据库中查找东西会很慢。

你可以通过给工厂一个输入流来从uri中获得位图，就像给工厂一个文件一样:

InputStream is = getContentResolver().openInputStream(uri);
Bitmap bitmap = BitmapFactory.decodeStream(is);
is.close();

像下面这样获取Uri。

//* get cursor like normal

Then

while (cursor.moveToNext()) {
    Uri uri = ContentUris.withAppendedId(
    MediaStore.Images.Media.EXTERNAL_CONTENT_URI, id);
}