Xamarin.Forms
Xamarin.Forms의 탐색

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뷰 모델에서 INavigation 사용

첫 번째 단계는 뷰 모델에서 사용할 탐색 인터페이스를 만드는 것입니다.

public interface IViewNavigationService
{
    void Initialize(INavigation navigation, SuperMapper navigationMapper);
    Task NavigateToAsync(object navigationSource, object parameter = null);
    Task GoBackAsync();
}

Initialize 메서드에서 필자는 사용자 정의 매퍼를 사용하여 페이지 유형 모음을 관련 키와 함께 유지합니다.

public class SuperMapper
{
    private readonly ConcurrentDictionary<Type, object> _typeToAssociateDictionary = new ConcurrentDictionary<Type, object>();

    private readonly ConcurrentDictionary<object, Type> _associateToType = new ConcurrentDictionary<object, Type>();

    public void AddMapping(Type type, object associatedSource)
    {
        _typeToAssociateDictionary.TryAdd(type, associatedSource);
        _associateToType.TryAdd(associatedSource, type);
    }

    public Type GetTypeSource(object associatedSource)
    {
        Type typeSource;
        _associateToType.TryGetValue(associatedSource, out typeSource);

        return typeSource;
    }

    public object GetAssociatedSource(Type typeSource)
    {
        object associatedSource;
        _typeToAssociateDictionary.TryGetValue(typeSource, out associatedSource);

        return associatedSource;
    }
}

열거 형 페이지 수 :

public enum NavigationPageSource
{
    Page1,
    Page2
}

App.cs 파일 :

public class App : Application
{
    public App()
    {
        var startPage = new Page1();
        InitializeNavigation(startPage);
        MainPage = new NavigationPage(startPage);
    }

    #region Sample of navigation initialization
    private void InitializeNavigation(Page startPage)
    {
        var mapper = new SuperMapper();
        mapper.AddMapping(typeof(Page1), NavigationPageSource.Page1);
        mapper.AddMapping(typeof(Page2), NavigationPageSource.Page2);

        var navigationService = DependencyService.Get<IViewNavigationService>();
        navigationService.Initialize(startPage.Navigation, mapper);
    } 
    #endregion
}

mapper에서는 enum 값을 가진 일부 페이지 유형을 연관시켰다.

IViewNavigationService 구현 :

[assembly: Dependency(typeof(ViewNavigationService))]
namespace SuperForms.Core.ViewNavigation
{
    public class ViewNavigationService : IViewNavigationService
    {
        private INavigation _navigation;
        private SuperMapper _navigationMapper;

        public void Initialize(INavigation navigation, SuperMapper navigationMapper)
        {
            _navigation = navigation;
            _navigationMapper = navigationMapper;
        }

        public async Task NavigateToAsync(object navigationSource, object parameter = null)
        {
            CheckIsInitialized();

            var type = _navigationMapper.GetTypeSource(navigationSource);

            if (type == null)
            {
                throw new InvalidOperationException(
                    "Can't find associated type for " + navigationSource.ToString());
            }

            ConstructorInfo constructor;
            object[] parameters;

            if (parameter == null)
            {
                constructor = type.GetTypeInfo()
                                  .DeclaredConstructors
                                  .FirstOrDefault(c => !c.GetParameters().Any());

                parameters = new object[] { };
            }
            else
            {
                constructor = type.GetTypeInfo()
                                  .DeclaredConstructors
                                  .FirstOrDefault(c =>
                                    {
                                        var p = c.GetParameters();
                                        return p.Count() == 1 &&
                                            p[0].ParameterType == parameter.GetType();
                                    });

                parameters = new[] { parameter };
            }

            if (constructor == null)
            {
                throw new InvalidOperationException(
                    "No suitable constructor found for page " + navigationSource.ToString());
            }

            var page = constructor.Invoke(parameters) as Page;

            await _navigation.PushAsync(page);
        }

        public async Task GoBackAsync()
        {
            CheckIsInitialized();

            await _navigation.PopAsync();
        }

        private void CheckIsInitialized()
        {
            if (_navigation == null || _navigationMapper == null)
                throw new NullReferenceException("Call Initialize method first.");
        }
    }
}

나는 사용자가 탐색하고 그것을 반사를 사용하여 인스턴스를 만들려는 페이지 유형을 얻습니다.

그리고 뷰 모델에서 네비게이션 서비스를 사용할 수 있습니다.

var navigationService = DependencyService.Get<IViewNavigationService>();
await navigationService.NavigateToAsync(NavigationPageSource.Page2, "hello from Page1");