刷新頁面 PopAsync()

Question

我有一個捕獲數字簽名的屏幕，在保存或返回時，當屏幕返回給我時執行 postasync 或 postmodalasync 不會重新加載。 如何使頁面重新加載或刷新？

 <Grid BackgroundColor="WhiteSmoke" Padding="0" RowSpacing="0" VerticalOptions="StartAndExpand">
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>
            <ContentView Margin="10,0,10,5" Padding="0" BackgroundColor="LightGray" HeightRequest="500">
                    <StackLayout Padding="5,0,5,5" BackgroundColor="White" Spacing="1">
                        <Label 
                Text="Firma Policia Que Realizo Visita"
                HorizontalOptions="Center"
                TextColor="Black" 
                FontSize="Large" 
                FontAttributes="Bold"

                 />

                    <Frame  HasShadow="true" 
                         Padding="8"
                        VerticalOptions="CenterAndExpand">
                        <signature:SignaturePadView  
                            x:Name="SignatureView" 

                            BindingContext="{Binding SignatureView}"
                            WidthRequest="280"
                        HeightRequest="300"
                            CaptionText="" 
                            CaptionTextColor="Blue" 
                            ClearText=""
                            PromptText=""
                            PromptTextColor="Green" 
                            BackgroundColor="WhiteSmoke" 
                            SignatureLineColor="Black" 
                            StrokeWidth="3" 
                            StrokeColor="Black" />
                    </Frame>
                </StackLayout>
                </ContentView>


        </Grid>


        <StackLayout Orientation="Horizontal" Padding="2" Spacing="2">
            <Button 
                    HorizontalOptions="FillAndExpand"
                    HeightRequest="40"                
                    Text="Guardar"
                    TextColor="{x:StaticResource WhiteColor}"
                    FontSize="Small"
                    VerticalOptions="Center"
                    BackgroundColor="{x:StaticResource GreenButton}"
                 Clicked="Button_Clicked">

            </Button>
            <Button                  
                    HorizontalOptions="FillAndExpand"
                    HeightRequest="40"                
                    Text="Limpiar"
                    TextColor="{x:StaticResource WhiteColor}"
                    FontSize="Small"
                    VerticalOptions="Center"
                    BackgroundColor="{x:StaticResource SicoqYellowColor}"
                   Clicked="Button_Clicked_1">
            </Button>


        </StackLayout>

這是制作 backbuttoncommand 服務的視圖模型

public Task RemoveLastModalFromBack(object parameter,bool animated = false)
    {
        var mainPage = Application.Current.MainPage as NavigationView;
        if (mainPage != null)
        {
            mainPage.Navigation.PopAsync(animated);
        }

        return Task.FromResult(true);
    }

這是接收簽名數據的 ViewModel

 private async Task BackButton()
    {

        try
        {
            IsBusy = true;



            await NavigationService.RemoveLastModalFromBack(str3);

            o


        }
        catch (Exception e)
        {
            IsBusy = false;
            // await DialogService.DisplayAlertAsync("Error", e.Message, "Aceptar");

        }
        finally
        {
            IsBusy = false;
        }
    }

數字簽名母版頁是保存或返回數字簽名頁面重新加載時的數字簽名

Answer 1

你想達到像下面GIF那樣的結果嗎？

如果是這樣，您可以使用MessagingCenter來實現這一點。

我們可以使用MessagingCenter send方法，這是我在SignaturesPage的 Button 點擊​​事件中的代碼，使用MessagingCenter將數據發送到 MainPage。

     private async void Button_Clicked(object sender, EventArgs e)
    {
       //get stream of Signatures  from the pad
        Stream image = await SignaturePad.GetImageStreamAsync(SignatureImageFormat.Png);
        MessagingCenter.Send<Stream>(image, "Image");
        await Navigation.PopAsync();
    }

在 MainPage 中，我布局有Image等待來自SignaturesPage的流。

     <StackLayout>
    <!-- Place new controls here -->
    <Frame BorderColor="Orange"
           CornerRadius="10"
           HasShadow="True">
        <Button AutomationId="Mybutton" Text="Save" x:Name="Mybutton" HorizontalOptions="CenterAndExpand" Clicked="Mybutton_Clicked"/>
    </Frame>
    <Frame BorderColor="Orange"
           CornerRadius="10"
           HasShadow="True">
        <Image x:Name="MyImage" HeightRequest="500" WidthRequest="400"/>
    </Frame>


</StackLayout>

這是我在 MainPage 中的背景代碼。

   public partial class MainPage : ContentPage
  {
    public MainPage()
    {
        InitializeComponent();

        MessagingCenter.Subscribe<Stream>(this, "Image", (arg) =>
        {
            MyImage.Source = ImageSource.FromStream(() => arg);

        });

    }

    protected override void OnAppearing()
    {
        base.OnAppearing();
    }
    private  void Mybutton_Clicked(object sender, EventArgs e)
    {

        Navigation.PushAsync(new SignaturesPage());
    }
}