iOS推送通知在前台时未调用willPresentnotification代理方法

首先，需要在AppDelegate中注册用户通知设置，并将通知类型设置为alert、sound和badge：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
    [center requestAuthorizationWithOptions:(UNAuthorizationOptionAlert | UNAuthorizationOptionSound | UNAuthorizationOptionBadge) completionHandler:^(BOOL granted, NSError * _Nullable error) {
        if (!error) {
            [[UIApplication sharedApplication] registerForRemoteNotifications];
        }
    }];
    return YES;
}

- (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken {
    [self registerDeviceToken:deviceToken];
}

然后，需要在AppDelegate中实现UNUserNotificationCenterDelegate协议中的willPresentNotification方法：

- (void)userNotificationCenter:(UNUserNotificationCenter *)center willPresentNotification:(UNNotification *)notification withCompletionHandler:(void (^)(UNNotificationPresentationOptions))completionHandler{
    completionHandler(UNNotificationPresentationOptionSound | UNNotificationPresentationOptionAlert);
}

在方法中调用completionHandler，将UNNotificationPresentationOptionSound和UNNotificationPresentationOptionAlert作为参数传入即可。这将使应用在前台时显示通知。

最后，在AppDelegate中添加以下代码段：

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
    [[UNUserNotificationCenter currentNotificationCenter] getDeliveredNotificationsWithCompletionHandler:^(NSArray<UNNotification *> *notifications) {
        // 通知处理
    }];
}

这将在接收到远程通知时调用，并且允许进行处理或显示通知。

这样，应用程序在前台时收到推送通知时就会调用willPresentNotification代理方法了。