在Kitkat版本上应该使用新的SD Card API

BillL[Google]

大家好！

这是来自我的同事Steven Zhang 有关最近不少国内厂商提出的在Kitkat版本上使用新的SD Card API所碰到的问题的解释信息 - 很多使用老的API会碰到无法储存信息到外插的SD卡。希望这个信息对国内的开发者们有参考价值：

Recently, some of the OEM like Huawei, Lenovo, ZTE raised their concern about our new external SD Card API and permission change in Kitkat.

Start from Kitkat, we have adjusted the extermal SD Card access API. In the http://developer.android.com/about/versions/android-4.4.html , we have the following info:

If your app reads from external storage...

Your app can not read shared files on the external storage when running on Android 4.4, unless your app has theREAD_EXTERNAL_STORAGE permission. That is, files within the directory returned bygetExternalStoragePublicDirectory() are no longer accessible without the permission. However, if you need to access only your app-specific directories, provided by getExternalFilesDir(), then you do not need theREAD_EXTERNAL_STORAGE permission.

More info can be found at http://developer.android.com/training/basics/data-storage/files.html .

This means only preloaded app can have full access.  And 3rd party apps will only have full access for their private data or read access for public folders in external storage.

The OEMs have tested their Kitkat devices against the popular apps, they found a lot of issue. Except the ES File Manager, other popular apps like wechat, sina weibo, QQ, Baidu video, Kugou...., they are still using old API. So this means they can not access the files on the external sdcard.  And, some apps will download files into external sdcard will totally fail.

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