下面是一个使用MediaStore获取按文件夹名称选择视频的示例代码：

首先，在AndroidManifest.xml文件中添加以下权限：

然后，在你的Activity中，可以使用以下代码来获取按文件夹名称选择视频：

import android.content.ContentResolver;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.provider.MediaStore;
import android.util.Log;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class VideoFolderPicker {

    public static List> getVideoFolders(Context context) {
        List> videoFolders = new ArrayList<>();
        ContentResolver contentResolver = context.getContentResolver();
        Uri uri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
        String[] projection = {
                MediaStore.Video.Media.BUCKET_ID,
                MediaStore.Video.Media.BUCKET_DISPLAY_NAME,
                "COUNT(*) AS " + MediaStore.Video.Media.DATA
        };
        String selection = "0==0) GROUP BY (" + MediaStore.Video.Media.BUCKET_ID;
        String sortOrder = MediaStore.Video.Media.DATE_MODIFIED + " DESC";
        Cursor cursor = contentResolver.query(uri, projection, selection, null, sortOrder);

        if (cursor != null) {
            while (cursor.moveToNext()) {
                String folderId = cursor.getString(cursor.getColumnIndex(MediaStore.Video.Media.BUCKET_ID));
                String folderName = cursor.getString(cursor.getColumnIndex(MediaStore.Video.Media.BUCKET_DISPLAY_NAME));
                String videoCount = cursor.getString(cursor.getColumnIndex(MediaStore.Video.Media.DATA));

                Map folder = new HashMap<>();
                folder.put("folderId", folderId);
                folder.put("folderName", folderName);
                folder.put("videoCount", videoCount);
                videoFolders.add(folder);
            }
            cursor.close();
        }
        return videoFolders;
    }
}

你可以在你的Activity中调用getVideoFolders方法来获取视频文件夹列表。例如：

List> videoFolders = VideoFolderPicker.getVideoFolders(this);
for (Map folder : videoFolders) {
    String folderId = folder.get("folderId");
    String folderName = folder.get("folderName");
    String videoCount = folder.get("videoCount");
    Log.d("VideoFolderPicker", "Folder ID: " + folderId + ", Folder Name: " + folderName + ", Video Count: " + videoCount);
}

这将打印出视频文件夹的ID、名称和包含的视频数量。

请注意，此代码使用MediaStore.Video.Media.EXTERNAL_CONTENT_URI来获取外部存储中的视频。如果你还想获取内部存储的视频，可以使用MediaStore.Video.Media.INTERNAL_CONTENT_URI。