挂载/卸载卷的unmount服务在4.4 Android上不起作用

Question

我使用反射挂载/卸载外部storage.it的版本低于4.4 Api。代码如下

import android.os.IBinder;
import android.os.RemoteException;
import android.os.ServiceManager;            
import android.os.storage.IMountService; 


private static final String MOUNT_POINT = "/mnt/ext_usb" or "/mnt/sdcard/" ...
private IMountService mMountService = null;

private synchronized IMountService getMountService() {
    if (mMountService == null) {
        IBinder service = ServiceManager.getService("mount");
        if (service != null) {
            mMountService = IMountService.Stub.asInterface(service);
        } else {
            Log.e(TAG, "Can't get mount service");
        }
    }
    return mMountService;
}

private void mount() {
    IMountService mountService = getMountService();
    try {
        if (mountService != null) {
            mountService.mountVolume(MOUNT_POINT);
        } else {
            //
        }
    } catch (RemoteException ex) {
        // Not much can be done
    }
}

private void unmount() {
    StorageManager sm = (StorageManager) getSystemService(Context.STORAGE_SERVICE);
    String state = sm.getVolumeState(MOUNT_POINT);
    if (!Environment.MEDIA_MOUNTED.equals(state) &&
            !Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
        //
        return;
    }

    IMountService mountService = getMountService();
    try {
        if (mountService != null) {
            mountService.unmountVolume(MOUNT_POINT, true, false);
        } else {
            Log.e(TAG, "Mount service is null, can't unmount");
        }
    } catch (RemoteException ex) {
        // Not much can be done
    }
}

任何获得它的解决方法都会抛出安全保护要求。我已经在清单中声明了这一点。我向谷歌了解了这个问题，我发现权限有working.As |signature Exception.android.permission.mount_unmount_filesystems level.Thanks。

Answer 1

为了使用具有signature | system权限的东西，您的包必须由平台的签名密钥签名。除非您正在创建自己的自定义ROM或具有根设备，否则您将无法做到这一点。

如果你的应用程序是一个常规的第三方应用程序(在Play商店发布)，那么你应该只使用公共API，而不是依赖于反射。只有公开的Android API被认为是稳定和公开的。另一些则是隐藏的，因为它们仅供系统内部使用。