Android 环境中的NPE。getExternalStorageState（）？

找不到获取“空指针异常”的原因。我可以显式地检查“getStorageState是否为null”，但这并不能解释为什么会出现此错误。 错误是：

java.lang.NullPointerException
at android.os.Environment.getStorageState(Environment.java:719)
at android.os.Environment.getExternalStorageState(Environment.java:694)
at com.ciqual.android.insight.sessionService.RemoveFiles(SessionService.java:664)
com.vyshas.android.sessionService.onEndSession(SessionService.java:460)

at:（错误指向的行是：）（见Jellybean4.3和kitkat）

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Environment.MEDIA_MOUNTED.equals（Environment.getExternalStorageState）不会导致NPE，而Environment.getExternalStorageState（）.equals（Environment.MEDIA_MOUNTED）会导致NPE并使应用程序崩溃

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我仍然不知道为什么getExternalStorageState为空，即使我设置了权限，但解决方案至少不会使应用程序崩溃。

我从Android 4.3获得了类似的报告

源代码是：

    /**
     * Gets the current state of the primary "external" storage device.
     *
     * @see #getExternalStorageDirectory()
     */
    public static String getExternalStorageState() {
        try {
            IMountService mountService = IMountService.Stub.asInterface(ServiceManager
                    .getService("mount"));
            final StorageVolume primary = getPrimaryVolume();
            return mountService.getVolumeState(primary.getPath());
        } catch (RemoteException rex) {
            Log.w(TAG, "Failed to read external storage state; assuming REMOVED: " + rex);
            return Environment.MEDIA_REMOVED;
        }
    }

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我无事可做，只能试着抓住它。

你在运行什么版本的Android？另外，为了确认一下，你是说你的代码片段的第一行在第719行吗？你能发布你的完整堆栈跟踪吗？@cybersam:它出现在android 4.3和4中。4@nKn已添加堆栈跟踪…我认为如果条件是（Environment.MEDIA_MOUNTED）.equals（Environment.getExternalStorageState）它不会停止执行流，也不会导致NPE崩溃。。。

    /**
     * Gets the current state of the primary "external" storage device.
     *
     * @see #getExternalStorageDirectory()
     */
    public static String getExternalStorageState() {
        try {
            IMountService mountService = IMountService.Stub.asInterface(ServiceManager
                    .getService("mount"));
            final StorageVolume primary = getPrimaryVolume();
            return mountService.getVolumeState(primary.getPath());
        } catch (RemoteException rex) {
            Log.w(TAG, "Failed to read external storage state; assuming REMOVED: " + rex);
            return Environment.MEDIA_REMOVED;
        }
    }