从图片网址获取缩略图网址

Question

我有一个字符串URL指向存储在我的设备的外部存储器上的图像:

String imageUrl = "/storage/emulated/0/DCIM/100MEDIA/IMAG0823.jpg"

我想获得查询MediaStore以获取此图像的缩略图.这就是我现在所做的:

private String getImageThumbnailPath(Context ctx, String imageUrl){

    Cursor cursor = MediaStore.Images.Thumbnails.queryMiniThumbnails(
            ctx.getContentResolver(), Uri.fromFile(new File(imageUrl)),
            MediaStore.Images.Thumbnails.MICRO_KIND,
            null);

    String url = "";
    if( cursor != null && cursor.getCount() > 0 ) {
        cursor.moveToFirst();
        url = cursor.getString( cursor.getColumnIndex( MediaStore.Images.Thumbnails.DATA ) );
        cursor.close();
    }
    return url;
} 

但是,调用此方法并打印它的内容不显示任何内容(光标为空).

如何查询MediaStore与我的图片网址相关联的缩略图网址？

编辑

我还尝试直接从图像URL解析Uri,如下所示:

Cursor cursor = MediaStore.Images.Thumbnails.queryMiniThumbnails(
        ctx.getContentResolver(), Uri.parse(imageUrl),
        MediaStore.Images.Thumbnails.MINI_KIND,
        null);

但结果是一样的.

Answer 1

如果您从图库中选择图像,则以下代码有效,否则我们无法使用缩略图,我们必须创建缩略图.

首先,您必须找到MediaStore.Images.Media._ID

public String[] getRealPathFromURI(Uri contentUri) {
    String[] proj = { MediaStore.Images.Media.DATA,
            MediaStore.Images.Media._ID };
    Cursor cursor = getActivity().getContentResolver().query(contentUri,
            proj, null, null, null);
    int path_index = cursor.getColumnIndexOrThrow(proj[0]);
    int id_index = cursor.getColumnIndexOrThrow(proj[1]);
    cursor.moveToFirst();
    return new String[] { cursor.getString(path_index),
            cursor.getLong(id_index) + "" };
}

从上面getRealPathFromURI我们现在MediaStore.Images.Media._ID,使用此ID来查找缩略图.

public static Bitmap getThumbnail(ContentResolver contentResolver, long id) {
        Cursor cursor = contentResolver.query(
                MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                new String[]{MediaStore.Images.Media.DATA}, // Which columns
                // to return
                MediaStore.Images.Media._ID + "=?", // Which rows to return
                new String[]{String.valueOf(id)}, // Selection arguments
                null);// order

        if (cursor != null && cursor.getCount() > 0) {
            cursor.moveToFirst();
            String filePath = cursor.getString(0);
            cursor.close();
            int rotation = 0;
            try {
                ExifInterface exifInterface = new ExifInterface(filePath);
                int exifRotation = exifInterface.getAttributeInt(
                        ExifInterface.TAG_ORIENTATION,
                        ExifInterface.ORIENTATION_UNDEFINED);
                if (exifRotation != ExifInterface.ORIENTATION_UNDEFINED) {
                    switch (exifRotation) {
                        case ExifInterface.ORIENTATION_ROTATE_180:
                            rotation = 180;
                            break;
                        case ExifInterface.ORIENTATION_ROTATE_270:
                            rotation = 270;
                            break;
                        case ExifInterface.ORIENTATION_ROTATE_90:
                            rotation = 90;
                            break;
                    }
                }
            } catch (IOException e) {
                Log.e("getThumbnail", e.toString());
            }
            Bitmap bitmap = MediaStore.Images.Thumbnails.getThumbnail(
                    contentResolver, id,
                    MediaStore.Images.Thumbnails.MINI_KIND, null);
            if (rotation != 0) {
                Matrix matrix = new Matrix();
                matrix.setRotate(rotation);
                bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
                        bitmap.getHeight(), matrix, true);
            }
            return bitmap;
        } else
            return null;
    }

要使用上面的LOC

更新

String[] imageInfo = getRealPathFromURI(Uri.parse("YOUR_IMAGE_PATH"));
yourImageView.setImageBitmap(getThumbnail(getActivity()
                    .getContentResolver(), Long.parseLong(imageInfo[1])));

Uri.parse("YOUR_IMAGE_PATH") 是contentUri

Answer 2

我确信ThumbnailUtils类可以在这方面为您提供帮助。

Bitmap thumb = ThumbnailUtils.extractThumbnail(BitmapFactory.decodeFile(imagePath), THUMBSIZE, THUMBSIZE);

它返回一个位图，您应该在使用它之前检查它是否不为空。有时，损坏的文件会返回空缩略图。

如果您不支持 API 级别 8 以下的任何内容，则应该使用它。

更新

如果您需要缩略图路径，请使用此方法，

public String getThumbnailPath(Uri uri) {
    String[] projection = { MediaStore.Images.Media._ID };
    String result = null;
    Cursor cursor = managedQuery(uri, projection, null, null, null);
    int column_index = cursor
            .getColumnIndexOrThrow(MediaStore.Images.Media._ID);

    cursor.moveToFirst();
    long imageId = cursor.getLong(column_index);
    cursor.close();

    cursor = MediaStore.Images.Thumbnails.queryMiniThumbnail(
            getContentResolver(), imageId,
            MediaStore.Images.Thumbnails.MINI_KIND,
            null);
    if (cursor != null && cursor.getCount() > 0) {
        cursor.moveToFirst();
        result = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails.DATA));
        cursor.close();
    }
    return result;
}