Pou's IT Life

public sealed partial class HubPage : Page

{

    private readonly ObservableDictionary defaultViewModel = new ObservableDictionary();

    /// <summary>

    /// Gets the view model for this <see cref="Page"/>.

    /// This can be changed to a strongly typed view model.

    /// </summary>

    public ObservableDictionary DefaultViewModel

    {

        get { return this.defaultViewModel; }

    }

    /// <summary>

    /// Populates the page with content passed during navigation.  Any saved state is also

    /// provided when recreating a page from a prior session.

    /// </summary>

    /// <param name="sender">

    /// The source of the event; typically <see cref="NavigationHelper"/>

    /// </param>

    /// <param name="e">Event data that provides both the navigation parameter passed to

    /// <see cref="Frame.Navigate(Type, Object)"/> when this page was initially requested and

    /// a dictionary of state preserved by this page during an earlier

    /// session.  The state will be null the first time a page is visited.</param>

    private async void NavigationHelper_LoadState(object sender, LoadStateEventArgs e)

    {

        // TODO: Create an appropriate data model for your problem domain to replace the sample data

        var sampleDataGroups = await SampleDataSource.GetGroupsAsync();

        this.DefaultViewModel["Groups"] = sampleDataGroups;

    }

}

private readonly NavigationHelper navigationHelper;

public NavigationHelper NavigationHelper

{

    get { return this.navigationHelper; }

}

public HubPage()

{

    this.InitializeComponent();

    // 實例化 NaivgationHelper 與註冊必要的事件；

    this.navigationHelper = new NavigationHelper(this);

    this.navigationHelper.LoadState += this.NavigationHelper_LoadState;

    this.navigationHelper.SaveState += this.NavigationHelper_SaveState;

}        

protected override void OnNavigatedTo(NavigationEventArgs e)

{

    this.navigationHelper.OnNavigatedTo(e);

}

protected override void OnNavigatedFrom(NavigationEventArgs e)

{

    this.navigationHelper.OnNavigatedFrom(e);

}

private async void NavigationHelper_LoadState(object sender, LoadStateEventArgs e)

{

    // 從 LoadStateEventArgs 取得保存起來的狀態值； PageState

}

private void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)

{

    // 將要保存的狀態值加以寫入；PageState

}

#region Process lifetime management

private String _pageKey;

/// <summary>

/// Register this event on the current page to populate the page

/// with content passed during navigation as well as any saved

/// state provided when recreating a page from a prior session.

/// </summary>

public event LoadStateEventHandler LoadState;

/// <summary>

/// Register this event on the current page to preserve

/// state associated with the current page in case the

/// application is suspended or the page is discarded from

/// the navigaqtion cache.

/// </summary>

public event SaveStateEventHandler SaveState;

/// <summary>

/// Invoked when this page is about to be displayed in a Frame.  

/// This method calls <see cref="LoadState"/>, where all page specific

/// navigation and process lifetime management logic should be placed.

/// </summary>

/// <param name="e">Event data that describes how this page was reached.  The Parameter

/// property provides the group to be displayed.</param>

public void OnNavigatedTo(NavigationEventArgs e)

{

    var frameState = SuspensionManager.SessionStateForFrame(this.Frame);

    this._pageKey = "Page-" + this.Frame.BackStackDepth;

    if (e.NavigationMode == NavigationMode.New)

    {

        // Clear existing state for forward navigation when adding a new page to the

        // navigation stack

        var nextPageKey = this._pageKey;

        int nextPageIndex = this.Frame.BackStackDepth;

        while (frameState.Remove(nextPageKey))

        {

            nextPageIndex++;

            nextPageKey = "Page-" + nextPageIndex;

        }

        // Pass the navigation parameter to the new page

        if (this.LoadState != null)

        {

            this.LoadState(this, new LoadStateEventArgs(e.Parameter, null));

        }

    }

    else

    {

        // Pass the navigation parameter and preserved page state to the page, using

        // the same strategy for loading suspended state and recreating pages discarded

        // from cache

        if (this.LoadState != null)

        {

            this.LoadState(this, new LoadStateEventArgs(e.Parameter, (Dictionary<String, Object>)frameState[this._pageKey]));

        }

    }

}

/// <summary>

/// Invoked when this page will no longer be displayed in a Frame.

/// This method calls <see cref="SaveState"/>, where all page specific

/// navigation and process lifetime management logic should be placed.

/// </summary>

/// <param name="e">Event data that describes how this page was reached.  The Parameter

/// property provides the group to be displayed.</param>

public void OnNavigatedFrom(NavigationEventArgs e)

{

    var frameState = SuspensionManager.SessionStateForFrame(this.Frame);

    var pageState = new Dictionary<String, Object>();

    if (this.SaveState != null)

    {

        this.SaveState(this, new SaveStateEventArgs(pageState));

    }

    frameState[_pageKey] = pageState;

}

#endregion

private async void NavigationHelper_LoadState(object sender, LoadStateEventArgs e)

{

    // 在 Page1 的 LoadState 時取得在離開 Page1 時呼叫 SaveState 所保存的資料

    if (e.PageState != null)

    {

        String myData = e.PageState["myData"].ToString();

    }

}

private void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)

{

    // 離開畫面時，先將畫面中的資料保存起來

    e.PageState["myData"] = "Pou";

}