安卓 4.4+ : check if path is on secondary storage

Question

当 Android 版本为 4.4+ 时，我的应用程序必须检查某个文件夹是否在辅助存储上。

我正在使用这个:

private boolean isPathOnSecondaryStorage(String path) {
    boolean res=false;
    String secondaryStorage=System.getenv("SECONDARY_STORAGE");
    String[] secondaryPaths=secondaryStorage.split(":");
    for (int i=0;i<secondaryPaths.length;i++) {
        String secondaryPath=secondaryPaths[i].trim();
        if (path.contains(secondaryPath)) {
            res=true;
        }
    }
    return res;
}

注意:

• 路径由用户通过文件选择器 Activity 选择，从/mnt 开始

• 应用想像往常一样检查挂载的内容，例如在其插槽中插入外部 SD 卡时

所以我问上面提到的代码是否总是能够检测路径何时在辅助存储上，或者在某些设备上它可以找到不同于/mnt (Android 4.4+) 的奇怪安装点。

Answer 1

这是我目前的解决方案。不理想，但应该可以。

/**
 * Uses the Environmental variable "SECONDARY_STORAGE" to locate a removable micro sdcard
 * 
 * @return  the primary secondary storage directory or
 *          {@code null} if there is no removable storage
 */
public static File getRemovableStorage() {
    final String value = System.getenv("SECONDARY_STORAGE");
    if (!TextUtils.isEmpty(value)) {
        final String[] paths = value.split(":");
        for (String path : paths) {
            File file = new File(path);
            if (file.isDirectory()) {
                return file;
            }
        }
    }
    return null;
}

/**
 * Checks if a file is on the removable SD card.
 * 
 * @see {@link Environment#isExternalStorageRemovable()}
 * @param file a {@link File}
 * @return {@code true} if file is on a removable micro SD card, {@code false} otherwise
 */
public static boolean isFileOnRemovableStorage(File file) {
    final File microSD = getRemovableStorage();
    if (microSD != null) {
        String canonicalPath;
        try {
            canonicalPath = file.getCanonicalPath();
            if (canonicalPath.startsWith(microSD.getAbsolutePath())) {
                return true;
            }
        } catch (IOException e) {
        }
    }
    return false;
}