注册

将UserControl通过RegisterForNavigation方法注册为Navigation

        protected override void RegisterTypes(IContainerRegistry containerRegistry)
        {
            containerRegistry.RegisterForNavigation<ViewA>();
            containerRegistry.RegisterForNavigation<ViewB>();
        }

导航视图

通过IRegionManager.RequestNavigate进行视图导航的切换
1、简单导航

        IRegionManager _regionManager;
        IRegionNavigationService _regionNavigationService;

        public NavigationWindowViewModel(IRegionManager regionManager, IRegionNavigationService regionNavigationService)
        {
            _regionManager = regionManager;
            _regionNavigationService = regionNavigationService;
        }
        
        private DelegateCommand _viewBCommand;

        public DelegateCommand ViewBCommand
        {
            get
            {
                if (_viewBCommand == null)
                    _viewBCommand = new DelegateCommand(() =>
                    {
                        // 导航到 ViewB
                        _regionManager.RequestNavigate("ContentRegion", "ViewB");
                    });
                ;
                return _viewBCommand;
            }
            set { _viewBCommand = value; }
        }

2、导航传参

• NavigationParameters：导航时传递参数
• Action< NavigationResult >：导航结束时的回调（导航的最后执行）

        private DelegateCommand<string> _viewACommand;

        public DelegateCommand<string> ViewACommand
        {
            get
            {
                if (_viewACommand == null)
                    _viewACommand = new DelegateCommand<string>((view) =>
                    {
                        // 导航到 ViewA
                        // NavigationParameters 传值
                        NavigationParameters param = new NavigationParameters();
                        param.Add("value", "123");
                        _regionManager.RequestNavigate("ContentRegion", "ViewB",
                            new Action<NavigationResult>((result) =>
                            {

                            }),
                            param);
                    });
                ;
                return _viewACommand;
            }
            set { _viewACommand = value; }
        }

INavigationAware

• IsNavigationTarget：控件View是重现（返回True）还是新建（返回False）
• OnNavigatedTo：获取导航传值、导航的日志记录（可前进或者后退）
• OnNavigatedFrom：触发时机不好阐述，最好调试看看

    public class ViewAViewModel : BindableBase, INavigationAware, IConfirmNavigationRequest
    {
        /// <summary>
        /// </summary>
        /// <param name="navigationContext"></param>
        public void OnNavigatedTo(NavigationContext navigationContext)
        {
            // 导航传值
            var param = navigationContext.Parameters["value"];

            // 历史记录
            _journal = navigationContext.NavigationService.Journal;
            //_journal.GoForward();
            //_journal.GoBack();
        }

        public bool IsNavigationTarget(NavigationContext navigationContext)
        {
            // 控件View是重现（返回True）还是新建（返回False）
            return true;
        }

        public void OnNavigatedFrom(NavigationContext navigationContext)
        {
            // navigationContext可以拿ViewA和ViewB两个对象
            // 触发时机
        }
   }

IConfirmNavigationRequest

导航某个页面，添加判断，是否是可以导航过去

    public class ViewAViewModel : BindableBase, INavigationAware, IConfirmNavigationRequest
    {
        // ===============================================IConfirmNavigationRequest
        public void ConfirmNavigationRequest(NavigationContext navigationContext, Action<bool> continuationCallback)
        {
            bool result = false;
            if (MessageBox.Show("数据没保存，是否离开", "确认", MessageBoxButton.YesNo) == MessageBoxResult.Yes)
            {
                // 允许导航
                result = true;
            }
            // 判断是否允许导航
            continuationCallback(result);
        }
   }

IRegionNavigationService和IRegionNavigationJournal

_regionManager.Regions[“ContentRegion”].NavigationService可以获得IRegionNavigationService对象；
IRegionNavigationService.Journal可以获得IRegionNavigationJournal对象；

        private DelegateCommand _forwordCommand;
        public DelegateCommand ForwordCommand
        {
            get
            {
                if (_forwordCommand == null)
                    _forwordCommand = new DelegateCommand(() =>
                    {
                        var j = _regionManager.Regions["ContentRegion"].NavigationService.Journal;
                        if (j.CanGoForward)
                            j.GoForward();
                    });
                return _forwordCommand;
            }
            set { _forwordCommand = value; }
        }
        
        private DelegateCommand _backCommand;
        public DelegateCommand BackCommand
        {
            get
            {
                if (_backCommand == null)
                    _backCommand = new DelegateCommand(() =>
                    {
                        //var j = _regionNavigationService.Journal;
                        var j = _regionManager.Regions["ContentRegion"].NavigationService.Journal;
                        if (j.CanGoBack)
                            j.GoBack();
                    });
                return _backCommand;
            }
            set { _backCommand = value; }
        }