Beispiel #1
0
        public async Task <bool> GoBack()
        {
            if (_isNavigating)
            {
                throw new InvalidOperationException("Navigation already in progress.");
            }

            _isNavigating    = true;
            this.CanNavigate = false;
            this.CanGoBack   = false;

            try
            {
                await this.WaitForLoadedAsync();

                AlternativePage currentPage = null;
                var             currentJe   = this.BackStack.Pop();
                var             je          = BackStack.Peek();

                if (_currentPagePresenter != null)
                {
                    currentPage = (AlternativePage)_currentPagePresenter.Content;
                    var cancelArgs =
                        new AlternativeNavigatingCancelEventArgs(
                            NavigationMode.Back,
                            je.Type);
                    await currentPage.OnNavigatingFromInternal(cancelArgs);

                    if (cancelArgs.Cancel)
                    {
                        this.BackStack.Push(currentJe);
                        return(false);
                    }
                }

                AlternativePage  newPage;
                ContentPresenter newPagePresenter;

                if (_preloadedPageCache.ContainsKey(je))
                {
                    newPagePresenter = _preloadedPageCache[je];
                    newPage          = (AlternativePage)newPagePresenter.Content;
                    _preloadedPageCache.Remove(je);
                }
                else
                {
                    newPage          = (AlternativePage)Activator.CreateInstance(je.Type);
                    newPage.Frame    = this;
                    newPagePresenter = new ContentPresenter {
                        Style = PagePresenterStyle
                    };
                    newPagePresenter.Content = newPage;
                    _pagePresentersPanel.Children.Add(newPagePresenter);
                }

                newPagePresenter.Opacity = 0.005;

                await UnloadPreloadedPages();

                var args = new AlternativeNavigationEventArgs(
                    newPage.Content, NavigationMode.New, je.Parameter, je.Type);
                await newPage.OnNavigatingToInternal(args);

                await newPagePresenter.WaitForLoadedAsync();

                await newPagePresenter.WaitForNonZeroSizeAsync();

                newPagePresenter.Opacity = 1.0;

                if (this.PageTransition != null)
                {
                    await this.PageTransition.TransitionBackward(_currentPagePresenter, newPagePresenter);
                }

                if (currentPage != null)
                {
                    await currentPage.OnNavigatedFromInternal(args);

                    _pagePresentersPanel.Children.Remove(_currentPagePresenter);
                }

                _currentPagePresenter = newPagePresenter;

                await newPage.OnNavigatedToInternal(args);

                return(true);
            }
            finally
            {
                _isNavigating    = false;
                this.CanNavigate = true;
                this.CanGoBack   = this.BackStack.Count > 1;
            }
        }
Beispiel #2
0
        private async Task <bool> NavigateCore(
            Type sourcePageType, object parameter, NavigationMode navigationMode)
        {
            _isNavigating         = true;
            this.CanNavigate      = false;
            this.CanGoBack        = false;
            this.CanGoForward     = false;
            this.IsHitTestVisible = false;

            // Make sure we run on UI thread
            if (!Dispatcher.HasThreadAccess)
            {
                Task <bool> navigateCoreTask = null;
                await Dispatcher.RunAsync(
                    CoreDispatcherPriority.High,
                    () => navigateCoreTask = NavigateCore(sourcePageType, parameter, navigationMode));

                return(await navigateCoreTask);
            }

            try
            {
                await _waitForApplyTemplateTaskSource.Task;
                await this.WaitForLoadedAsync();

                AlternativePage currentPage = null;

                #region OnNavigatingFrom part
                if (_currentPagePresenter != null)
                {
                    currentPage = (AlternativePage)_currentPagePresenter.Content;
                    var cancelArgs =
                        new AlternativeNavigatingCancelEventArgs(
                            navigationMode,
                            sourcePageType);
                    await this.OnNavigating(cancelArgs);

                    if (!cancelArgs.Cancel)
                    {
                        await currentPage.OnNavigatingFromInternal(cancelArgs);
                    }

                    if (cancelArgs.Cancel)
                    {
                        return(false);
                    }
                }
                #endregion

                #region Initializing new page instance part
                var je = new JournalEntry {
                    SourcePageType = sourcePageType, Parameter = parameter
                };
                AlternativePage  newPage;
                ContentPresenter newPagePresenter;

                if (_preloadedPageCache.ContainsKey(je))
                {
                    newPagePresenter = _preloadedPageCache[je];
                    newPage          = (AlternativePage)newPagePresenter.Content;
                    _preloadedPageCache.Remove(je);
                }
                else
                {
                    newPage = _frameCache.Get(je.SourcePageType);

                    if (newPage == null)
                    {
                        throw new InvalidOperationException(
                                  "Pages used in AlternativeFrame need to be of AlternativePage type.");
                    }

                    newPage.Frame    = this;
                    newPagePresenter = new ContentPresenter {
                        Style = PagePresenterStyle
                    };
                    newPagePresenter.Content = newPage;
                    _pagePresentersPanel.Children.Add(newPagePresenter);
                }

                newPagePresenter.Opacity = 0.005;

                await UnloadAllPreloaded();

                #endregion

                #region OnNavigatingTo part
                var args = new AlternativeNavigationEventArgs(
                    newPage.Content, navigationMode, je.Parameter, je.SourcePageType);
                await newPage.OnNavigatingToInternal(args);

                #endregion

                #region Journal Bookeeping part
                switch (navigationMode)
                {
                case NavigationMode.New:
                    this.ForwardStack.Clear();

                    if (this.CurrentJournalEntry != null)
                    {
                        this.BackStack.Push(this.CurrentJournalEntry);
                    }

                    break;

                case NavigationMode.Forward:
                    this.ForwardStack.Pop();

                    if (this.CurrentJournalEntry != null)
                    {
                        this.BackStack.Push(this.CurrentJournalEntry);
                    }

                    break;

                case NavigationMode.Back:
                    this.BackStack.Pop();

                    if (this.CurrentJournalEntry != null)
                    {
                        this.ForwardStack.Push(this.CurrentJournalEntry);
                    }

                    break;
                }

                this.CurrentJournalEntry = je;
                #endregion

                #region OnNavigated~() calls
                await this.OnNavigated(args);

                if (currentPage != null)
                {
                    await currentPage.OnNavigatedFromInternal(args);
                }

                await newPage.OnNavigatedToInternal(args);

                #endregion

                #region Transition part
                await newPagePresenter.WaitForLoadedAsync();

                await newPagePresenter.WaitForNonZeroSizeAsync();

                if (this.ShouldWaitForImagesToLoad == true &&
                    newPage.ShouldWaitForImagesToLoad != false ||
                    newPage.ShouldWaitForImagesToLoad == true &&
                    this.ShouldWaitForImagesToLoad != false)
                {
                    await newPage.WaitForImagesToLoad(WaitForImagesToLoadTimeout);
                }

                newPagePresenter.Opacity = 1.0;

                if (navigationMode == NavigationMode.Back)
                {
                    await TransitionBackward(
                        currentPage,
                        newPage,
                        _currentPagePresenter,
                        newPagePresenter);
                }
                else
                {
                    await TransitionForward(
                        currentPage,
                        newPage,
                        _currentPagePresenter,
                        newPagePresenter);
                }

                if (_currentPagePresenter != null)
                {
                    _pagePresentersPanel.Children.Remove(_currentPagePresenter);
                    _frameCache.Store(currentPage);
                }

                _currentPagePresenter = newPagePresenter;
                #endregion

                return(true);
            }
            finally
            {
                this.IsHitTestVisible = true;
                _isNavigating         = false;
                this.CanNavigate      = true;
                this.CanGoBack        = this.BackStack.Count > 0;
                this.CanGoForward     = this.ForwardStack.Count > 0;
                //DC.TraceLocalized(GetNavigationState());
            }
        }