How to open file manager and select specific file type in my app?

Question

I use the following code in my Android app to open the gallery and select a video file.

Now I want to modify this code to open the file manager, and select a file of specific type ( for example *.xyz). How can I do this !?

public View.OnClickListener btnChoosePhotoPressed = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent_file = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Video.Media.INTERNAL_CONTENT_URI);
            final int ACTIVITY_SELECT_IMAGE = 1234;
            startActivityForResult(intent_file, ACTIVITY_SELECT_IMAGE);
        }
    };


protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);    
        switch (requestCode) {
            case 1234:
                if (resultCode == RESULT_OK) {        

                    Uri selectedImage = data.getData();
                    String[] filePathColumn = {MediaStore.Video.Media.DATA};

                    Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);                        
                    cursor.moveToFirst();
                    int columnIndex = cursor.getColumnIndex(filePathColumn[0]);                        
                    final String filePath = cursor.getString(columnIndex);
                    cursor.close();

                    // Now I use filePath to access the file.

                }
        }
};

I searched for similar questions and this answer was helpful: Open Default File Manager in android? It helps to open the file manager. However, how can I handle the second part of my code about cursor, filePathColumn, and filepath !? I need the filePath to access the file.

Any help is highly appreciated.

---

EDIT 1 :

I changed my code to the following:

public View.OnClickListener btnChoosePhotoPressed = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent_file = new Intent();
            final int ACTIVITY_SELECT_IMAGE = 1234;
            intent_file.setAction(Intent.ACTION_GET_CONTENT);
            intent_file.setType("video/*");
            startActivityForResult(Intent.createChooser(intent_file, "Select Picture"),ACTIVITY_SELECT_IMAGE);
        }
    };


protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);    
        switch (requestCode) {
            case 1234:
                if (resultCode == RESULT_OK) {        

                    Uri selectedImage = data.getData();
                    final String filePath = selectedImage.getPath();

                }
        }
};

This time, it opens the file manager to select the file. But unfortunately, the filePath is somehow incorrect. Because later in my code, I use the following methods to send the file via sftp, which fails, and no file is transferred.

File file = new File(filePath);
FileInputStream fis = new FileInputStream(file);
channelSftp2.put(fis, file.getName());
fis.close();

So, any suggestions?