Android：外部存储权限问题：
我真的需要有人指导我解决外部存储或 SD 卡的一些问题。我不会讨论复杂性。我有一个名为 MyVideos 的文件夹。它位于 Motrola Xoom 的 SD 卡文件夹中；路径是 "/mnt/sdcard-ext/MyVideos. 该文件夹已经存在。但是，我遇到了一些奇怪的错误..例如，如果我检查该文件夹是否存在使用以下代码：
File myDirectory = new File(defaultStorage, "/MyVideos/");
if (myDirectory.exists())
{
my code: lets say true
}
else
{
my code: false
}
其中 defaultStorage is = "/mnt/sdcard-ext" 它总是返回 false。它应该返回 true，因为该文件夹确实存在于该文件夹中。 执行其他操作
for (File f : myDirectory.listFiles())
{
if (f.isFile())
{
filenames.add(f.getName()); //add to array
}//if closes
}//for closes
像我一样 以下行的致命异常
for (File f : myDirectory.listFiles())
错误堆栈如下：
E/AndroidRuntime(22644): FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity
E/AndroidRuntime(22644): Caused by: java.lang.NullPointerException
我刚刚提到了堆栈中重要的内容。准确地说，它是一个 NullPointerException，尽管我
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
在清单文件中使用它，但它不起作用。最令人惊讶的元素是它在这里运行良好；但有一个在美国的客户，它在他的所有设备上崩溃了。英国或其他国家的设备的权限设置有什么不同吗？美国..我将感谢如果你在这里帮助我的话..这对我来说是一个大问题。 谢谢
I really need someone here to guide me about some issues with the external storage OR sd-card. I won't go into complexities. I have a folder with the name of MyVideos. It is located in the sd-card folder of Motrola Xoom; the path is "/mnt/sdcard-ext/MyVideos. The folder is already there. However, there are some strange errors I am having.. For example, if I check if the folder exists or not using the following code:
File myDirectory = new File(defaultStorage, "/MyVideos/");
if (myDirectory.exists())
{
my code: lets say true
}
else
{
my code: false
}
where defaultStorage is = "/mnt/sdcard-ext". It always return false. It should return true since the folder surely exists there. And assuming that the folder exists there, I perform other operations like
for (File f : myDirectory.listFiles())
{
if (f.isFile())
{
filenames.add(f.getName()); //add to array
}//if closes
}//for closes
I get FATAL exception at the following line
for (File f : myDirectory.listFiles())
The error stack is below:
E/AndroidRuntime(22644): FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity
E/AndroidRuntime(22644): Caused by: java.lang.NullPointerException
I have just mentioned the things that are important from the stack. It is a NullPointerException to be precise. Although I am using
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
in my manifest file. Even then it doesn't work. The most surprising element is that it is running fine here; but there is a client in USA, it is crashing on all his devices.. Is there any difference in the permission settings of devices in UK or in USA.. I shall be thankful to you if you help me here.. It is a big problem for me.
Thanks
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根据 文档，您描述的状态意味着您无法访问外部媒体存储：
public static final String MEDIA_SHARED
添加到 API 级别 1 getExternalStorageState() 如果媒体存在且未安装且通过 USB 共享，则返回 MEDIA_SHARED海量存储。
常数值：“共享”
您需要转到 USB 大容量存储选项并关闭 USB 存储。
PS：感谢 DigCamara，我从这个 SO 答案复制。
谢谢
According to the documentation, the state you're describing means that the external media storage isn't accessible to you:
public static final String MEDIA_SHARED
Added in API level 1 getExternalStorageState() returns MEDIA_SHARED if the media is present not mounted, and shared via USB mass storage.
Constant Value: "shared"
You need to go to your USB Mass Storage options and turn off USB storage.
PS : Thanks to DigCamara I copied from this SO answer.
Thanks