ios 首次打开 App，不允许 扫码，引导用户去设置页面，开启相机权限

// #ifdef APP-PLUS

            var platform = plus.os.name  
            if(platform == 'iOS') {  
                var AVCaptureDevice = plus.ios.importClass('AVCaptureDevice')  
                var scaneState = AVCaptureDevice.authorizationStatusForMediaType('vide')  
                if (3 != scaneState) {  
                    uni.showModal({  
                        content: '需要访问您的相机，请到设置里开启',  
                        confirmText: '设置',  
                        success: res => {  
                            if(res.confirm) {  
                                plus.runtime.openURL('app-settings://')  
                            } else {  
                                uni.navigateBack({  
                                    delta: 1  
                                })  
                            }  
                        }  
                    });  
                }  
            }  
        // #endif  

AVAuthorizationStatusNotDetermined = 0,//用户暂时没有做相关选着  
AVAuthorizationStatusRestricted    = 1,//没有改媒体类型  
AVAuthorizationStatusDenied        = 2,//用户拒绝  
AVAuthorizationStatusAuthorized    = 3,//用户允许