如何在Android中收听新照片？

Question

我需要收听来自任何来源的新图像,例如下载图像,捕获新图像,其他应用程序下载图像等等.是否有任何监听器会在新图片添加到图库时触发事件？我一直在寻找两天.我无法得到任何可靠的东西.

我读到了 FileObserver,这会有帮助吗？

Answer 1

新照片到达画廊

意味着它已被添加到MediaStore.

首先,FileOberver是一种记忆杀手的方法.考虑大量文件.相反,ContentObserver似乎是一种更好的方法.

getContentResolver().registerContentObserver(android.provider.MediaStore.Images.Media.INTERNAL_CONTENT_URI, true, 
        new ContentObserver(new Handler()) {
            @Override
            public void onChange(boolean selfChange) {
                Log.d("your_tag","Internal Media has been changed");
                super.onChange(selfChange);
                Long timestamp = readLastDateFromMediaStore(context, MediaStore.Images.Media.INTERNAL_CONTENT_URI);
                // comapare with your stored last value and do what you need to do

            }
        }
    );
getContentResolver().registerContentObserver(android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI, true, 
    new ContentObserver(new Handler()) {
        @Override
        public void onChange(boolean selfChange) {
            Log.d("your_tag","External Media has been changed");
            super.onChange(selfChange);

            Long timestamp = readLastDateFromMediaStore(context, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
            // comapare with your stored last value and do what you need to do
        }
    }
);

private Long readLastDateFromMediaStore(Context context, Uri uri) {
        Cursor cursor = context.getContentResolver().query(uri, null, null, null, "date_added DESC");
        PhotoHolder media = null;
        Long dateAdded =-1;
        if (cursor.moveToNext()) {
            Long dateAdded = cursor.getLong(cursor.getColumnIndexOrThrow(MediaColumns.DATE_ADDED));         
        }
        cursor.close();
        return dateAdded;
}

在服务中执行此操作可能是一个好主意(永远运行)!您还需要取消注册onDestroy()

警告:这只会告诉您MediaStore何时更改,它没有任何关于添加/删除的具体信息.为此,您可能必须查询MediaStore以检测先前数据库或其他内容的任何更改.