读取系统所有 图片 和缩略图

    /**
       * 读取系统的 多媒体索引 获取 sd卡中的所有图片信息
       */
      public void initImagesIndex() {
            ImageCache. imgDirPathList = new ArrayList<String>();
            ImageCache. imagesIndex = new HashMap<String, List<Map<String, String>>>();
            ContentResolver cr = mContext.getContentResolver();
            String[] imagesProjection = { Images.ImageColumns. _ID, Images.ImageColumns.DATA , Images.ImageColumns.BUCKET_DISPLAY_NAME };
             // 查询sd上所有的图片信息
            Cursor cur = cr.query(Images.Media. EXTERNAL_CONTENT_URI, imagesProjection, null , null, null);
             if (cur.moveToFirst()) {
                   int _id; // 图片id
                  String data; // 图片Path 具体路径
                  String dirName; // 图片所在目录的名称
                   int _idColumn = cur.getColumnIndex(Images.ImageColumns._ID );
                   int data_idColcum = cur.getColumnIndex(Images.ImageColumns.DATA );
                   int dispalyname_Column = cur.getColumnIndex(Images.ImageColumns.BUCKET_DISPLAY_NAME );
                   do {
                        _id = cur.getInt(_idColumn);
                        data = cur.getString(data_idColcum);
                        dirName = cur.getString(dispalyname_Column);
                        HashMap<String, String> map = new HashMap<>();
                        map.put(CommonConst.ImageMap. ID, _id + "");
                        map.put(CommonConst.ImageMap. PATH, data);
                        map.put(CommonConst.ImageMap. DIR_NAME, dirName);
                         // 图片所在文件夹路径
                        String imgDirPath = data.substring(0, data.lastIndexOf("/" ));
                         if (!ImageCache.imagesIndex .containsKey(imgDirPath)) {
                               // 当找不到 该图片所在文件夹路径 时 则创建一个新的List 并且注入到 Map 中
                              List<Map<String, String>> list = new ArrayList<Map<String, String>>();
                              list.add(map);
                              ImageCache. imagesIndex.put(imgDirPath, list);
                              Log. i(TAG, "img dir path = " + imgDirPath);
                        } else {
                               // 找到的话 在原有的List 添加该图片信息
                              ImageCache. imagesIndex.get(imgDirPath).add(map);
                        }
                         // 给图片所在文件夹路径 List 添加值 便于 计算出 adapter 使用
                         if (!ImageCache.imgDirPathList .contains(imgDirPath)) {
                              ImageCache. imgDirPathList.add(imgDirPath);
                        }
                  } while (cur.moveToNext());
            }
            initImagesThumb();
      }

      /**
       * 初始化 读取 缩略图信息
       */
      public void initImagesThumb() {
            ContentResolver cr = mContext.getContentResolver();
            String[] imagesProjection = { Thumbnails. IMAGE_ID, Thumbnails.DATA };
            Cursor cur = cr.query(Thumbnails. EXTERNAL_CONTENT_URI, imagesProjection, null , null, null);
             if (cur.moveToFirst()) {
                  String imagID; // 图片Path 具体路径
                  String imgThumbPath; // 图片所在目录的名称
                   int imagID_column = cur.getColumnIndex(Thumbnails.IMAGE_ID );
                   int imgThumbPath_column = cur.getColumnIndex(Thumbnails.DATA );
                   do {
                        imagID = cur.getString(imagID_column);
                        imgThumbPath = cur.getString(imgThumbPath_column);
                        ImageCache. imgThumbMap.put(imagID, imgThumbPath);
                  } while (cur.moveToNext());
            }
      }