Xamarin Forms. Webview. Not injecting javascript

Question

I am trying to inject js into the webview. My goal is to inject custom js on the website loaded. I use following code to inject javascript to my simple webview in xamarin forms.

XAML:

<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:BrowserApp" x:Class="BrowserApp.Views.BrowserAppPage">

<StackLayout>
    <StackLayout Orientation="Horizontal">
    <Button Text="&lt;" HeightRequest="40" WidthRequest="40" Clicked="Back_Clicked"/>
    <Button Text="&gt;" HeightRequest="40" WidthRequest="40" Clicked="Forward_Clicked"/> 
        <Entry x:Name="url" WidthRequest="180" />
        <Button Text="Go" HeightRequest="40" WidthRequest="50" Clicked="Go_Clicked"/>
    </StackLayout>
    <Label x:Name="LoadingLabel" IsVisible="false"/>
        <WebView x:Name="Browser" HeightRequest="1000" WidthRequest="1000" Navigating="Handle_Navigating" Navigated="Handle_Navigated"/>
    </StackLayout>
</ContentPage>

XAML.CS:

using System.Threading.Tasks;
using Xamarin.Forms;

namespace BrowserApp.Views
{
    public partial class BrowserAppPage : ContentPage
    {
        public async void  Handle_Navigated(WebView sender, Xamarin.Forms.WebNavigatedEventArgs e)
        {
            await sender.EvaluateJavaScriptAsync("javascript:alert();");
            LoadingLabel.IsVisible = false;
        }

        void Handle_Navigating(object sender, Xamarin.Forms.WebNavigatingEventArgs e)
        {
            LoadingLabel.IsVisible = true;
        }

        void Go_Clicked(object sender, System.EventArgs e)
        {
            Browser.Source = url.Text;
        }

        void Forward_Clicked(object sender, System.EventArgs e)
        {
            if (Browser.CanGoForward)
                Browser.GoForward();
        }

        void Back_Clicked(object sender, System.EventArgs e)
        {
            if (Browser.CanGoBack)
                Browser.GoBack();
        }

        public BrowserAppPage()
        {
            InitializeComponent();
            url.Text = "https://google.com";
            Browser.Source = url.Text;

        }
    }
}

Somehow the js is not injected. Not even a simple alert works.

Edit: I checked the code on a android device, instead of UWP. On android it is working. Is there a way to enable javascript for the platforms?

Do you want the js works on all platform(iOS,android,uwp)? Have you test it ? — ColeX - MSFT
I have been working on UWP as preffered working platform. After setting up an android device I noticed that it must be a platform setting that suspends the js on UWP. (Haven't tested iOS yet) So, yes I am looking for to enable js on all platforms (iOS, android and uwp). — aiceg

ColeX - MSFT ColeX - MSFT · Accepted Answer · 2020-06-12T13:42:46

I test on iOS and Android , it works perfectly , but problem occurs on UWP .

I followed the link :, set IsJavaScriptAlertEnabled to true but no luck .

Tried

javascript:window.alert(123);
javascript:alert(123);
alert(123);"
window.alert(123);"

Problem persists !!!

We can invoke javascript on UWP(js works in this sample) ,so I think maybe the website blocks the alert function on UWP.

I've raised the issue on github, you could keep monitoring the issue .

Xamarin Forms. Webview. Not injecting javascript

1 Answers