uniMP.getAppid()的返回值为null

大佬们，帮忙看看为啥返回的事null呢

 try {  
            IUniMP uniMP = DCUniMPSDK.getInstance().openUniMP(mContext,"__UNI__ADC1D4B");  
            String appid = (String) uniMP.getAppid();  
            mUniMPCaches.put(uniMP.getAppid(), uniMP);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }

小程序打开了，但是uniMP.getAppid()的返回值为null返回null