Xamarin Forms WebView cache: GoBack() doesn't call Navigating event

Question

As I previously said in this question, I'm new at Xamarin.Forms and I'm developing a cross-platform web browser with Microsoft Visual Studio 2017 version 15.5.4. I'm debugging on an Android 5.1 smartphone.

In my layout there's a WebView and two Buttons to go back/forward.

<Button Image="backarrowdisabled.png"
        Grid.Row="1"
        Grid.Column="0"
        x:Name="backButton"
        IsEnabled="False"
        Clicked="previousPage">
    <Button.Triggers>
        <DataTrigger TargetType="Button"
                     Binding="{Binding CanGoBack, Source={Reference appWebView}}"
                     Value="False">
            <Setter Property="IsEnabled" Value="False" />
            <Setter Property="Image" Value="backarrowdisabled.png" />
        </DataTrigger>

        <DataTrigger TargetType="Button"
                     Binding="{Binding CanGoBack, Source={Reference appWebView}}"
                     Value="True">
            <Setter Property="IsEnabled" Value="True" />
            <Setter Property="Image" Value="backarrow.png" />
        </DataTrigger>
    </Button.Triggers>
</Button>


<Button Image="nextarrowdisabled.png"
        Grid.Row="1"
        Grid.Column="5"
        x:Name="nextButton"
        IsEnabled="False"
        Clicked="nextPage">
        /* triggers */   
</Button>

<WebView Grid.Row="3"
         Grid.Column="0"
         Grid.ColumnSpan="6"
         x:Name="appWebView"
         Source="https://www.google.it/"
         Navigating="onPageLoading"
         Navigated="onPageLoaded"/>

As you can see there are two methods to manage Navigating and Navigated events, which are

private void onPageLoading(object sender, WebNavigatingEventArgs e)
{
    URLEntry.Text = e.Url;      //Entry where I can see the page URL
    //other code
}

private void onPageLoaded(object sender, EventArgs e)
{
    //some code       
}

When I click on a link or something like that in my WebView everything works correctly, but when I have to go back/forward in my history the Entry doesn't update the URL to the previous/next one. It seems it doesn't even call the onPageLoading method, but the WebView loads the page.

These are the methods called by the Buttons

private void previousPage (object sender, EventArgs e)
{
    appWebView.GoBack();
}

private void nextPage (object sender, EventArgs e)
{
    appWebView.GoForward();
}

Is it a WebView bug or am I doing something wrong?

Edit: I think the pages are cached, is there a way to make it not do it?

Answer 1

One thing you can do, is to create another event handler for the WebView's PropertyChanged or PropertyChanging event. There, you can check to see if the Source property was changed; If so, you can update the TextView with the new source. (I'm not sure exactly, but it seems like whe navigating back or forward, the Navigating event does not get called, possibly because the page is already cached?)

See here: https://developer.xamarin.com/api/member/Xamarin.Forms.WebView.OnPropertyChanged/p/System.String/

So your code can look like

<WebView x:Name="MyWebView" PropertyChanged="OnWebViewPropertyChanged" />

and then your code behind:

private void OnWebViewPropertyChanged(object sender, PropertyChangedEventArgs e)
{
    if (e.PropertyName == WebView.SourceProperty.PropertyName)
    {
        URLEntry.Text = MyWebView.Source.ToString(); // May need to check this
    }
}