如何判断SD卡是否已安装在Android中？

Question

我正在开发一个Android应用程序,需要查看用户存储的图像.问题是如果用户通过USB线安装了SD卡,我就无法读取磁盘上的图像列表.

有没有人知道如何判断usb是否已安装,以便我可以弹出一条消息通知用户它不起作用？

Answer 1

如果您尝试访问设备上的图像,最好的方法是使用MediaStore内容提供商.将其作为内容提供者访问将允许您查询存在的图像,并content://在适当的位置将URL 映射到设备上的文件路径.

如果您仍然需要访问SD卡,则Camera应用程序包含一个ImageUtils类,用于检查SD卡是否按如下方式安装:

static public boolean hasStorage(boolean requireWriteAccess) {
    //TODO: After fix the bug,  add "if (VERBOSE)" before logging errors.
    String state = Environment.getExternalStorageState();
    Log.v(TAG, "storage state is " + state);

    if (Environment.MEDIA_MOUNTED.equals(state)) {
        if (requireWriteAccess) {
            boolean writable = checkFsWritable();
            Log.v(TAG, "storage writable is " + writable);
            return writable;
        } else {
            return true;
        }
    } else if (!requireWriteAccess && Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
        return true;
    }
    return false;
}

Answer 2

这是jargonjustinpost中的checkFsWritable缺失函数

private static boolean checkFsWritable() {
        // Create a temporary file to see whether a volume is really writeable.
        // It's important not to put it in the root directory which may have a
        // limit on the number of files.
        String directoryName = Environment.getExternalStorageDirectory().toString() + "/DCIM";
        File directory = new File(directoryName);
        if (!directory.isDirectory()) {
            if (!directory.mkdirs()) {
                return false;
            }
        }
        return directory.canWrite();
    }