Android:如何查询存储桶名称列表

Question

我只想检索存储桶的名称(专辑)。例如。相机、下载等但不是所有照片的相机、下载等列表，那么如何为每个存储桶名称检索一行？

我的意思是像在 Gallery 应用程序中，你首先有相册，例如相机。当你点击它时，它会显示相机的所有照片。

我可以使用查询的 Where 子句查询相机胶卷中的照片。但是，如果我只想要每个相册的名称而不是照片，是否可以查询呢？如果我查询所有的照片，每组照片只取一行，那会很耗时。

请帮忙

Answer 1

我有同样的问题，这是我的解决方案(在跟踪图库源代码之后)获取相册名称和其中的第一张图片(可以用作该相册的缩略图):

(请注意，桶重复已通过 groupby 和排序技术删除)

    // which image properties are we querying
    String[] PROJECTION_BUCKET = {
            ImageColumns.BUCKET_ID,
            ImageColumns.BUCKET_DISPLAY_NAME,
            ImageColumns.DATE_TAKEN,
            ImageColumns.DATA};
    // We want to order the albums by reverse chronological order. We abuse the
    // "WHERE" parameter to insert a "GROUP BY" clause into the SQL statement.
    // The template for "WHERE" parameter is like:
    //    SELECT ... FROM ... WHERE (%s)
    // and we make it look like:
    //    SELECT ... FROM ... WHERE (1) GROUP BY 1,(2)
    // The "(1)" means true. The "1,(2)" means the first two columns specified
    // after SELECT. Note that because there is a ")" in the template, we use
    // "(2" to match it.
    String BUCKET_GROUP_BY =
            "1) GROUP BY 1,(2";
    String BUCKET_ORDER_BY = "MAX(datetaken) DESC";

    // Get the base URI for the People table in the Contacts content provider.
    Uri images = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;

    Cursor cur = getContentResolver().query(
            images, PROJECTION_BUCKET, BUCKET_GROUP_BY, null, BUCKET_ORDER_BY);

    Log.i("ListingImages"," query count=" + cur.getCount());

    if (cur.moveToFirst()) {
        String bucket;
        String date;
        String data;
        int bucketColumn = cur.getColumnIndex(
                MediaStore.Images.Media.BUCKET_DISPLAY_NAME);

        int dateColumn = cur.getColumnIndex(
                MediaStore.Images.Media.DATE_TAKEN);
        int dataColumn = cur.getColumnIndex(
                MediaStore.Images.Media.DATA);

        do {
            // Get the field values
            bucket = cur.getString(bucketColumn);
            date = cur.getString(dateColumn);
            data = cur.getString(dataColumn);

            // Do something with the values.
            Log.i("ListingImages", " bucket=" + bucket 
                    + "  date_taken=" + date
                    + "  _data=" + data);
        } while (cur.moveToNext());
    }