I am using a custom WebView in my .NET MAUI application to display dynamic HTML content on iOS. The HTML content changes daily, and I need to adjust the height of the WebView accordingly.
Custom WebView Renderer (iOS)
Here’s my custom WebViewRenderer implementation:
public class MyWebViewRenderer : ViewRenderer<MyWebView, WKWebView>
{
WKWebView _wkWebView;
protected override void OnElementChanged(ElementChangedEventArgs<MyWebView> e)
{
base.OnElementChanged(e);
if (Control == null)
{
var config = new WKWebViewConfiguration();
config.AllowsInlineMediaPlayback = true;
_wkWebView = new WKWebView(Frame, config);
//transparent background
_wkWebView = new WKWebView(CGRect.Empty, config);
_wkWebView.BackgroundColor = UIColor.Clear;
_wkWebView.ScrollView.BackgroundColor = UIColor.Clear;
_wkWebView.ScrollView.ScrollEnabled = false;
_wkWebView.Opaque = false;
_wkWebView.NavigationDelegate = new MyNavigationDelegate();
SetNativeControl(_wkWebView);
if (Device.Idiom == TargetIdiom.Tablet)
{
//when targeting on iPad, add this to force the iPad behavior
_wkWebView.Configuration.DefaultWebpagePreferences.PreferredContentMode = WKContentMode.Mobile;
}
SetNativeControl(_wkWebView);
}
}
public class MyNavigationDelegate : WKNavigationDelegate
{
public override void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
{
string fontSize = "";
if (Device.Idiom == TargetIdiom.Phone)
{
fontSize = "500%"; // > 100% shows larger than previous
}
else if (Device.Idiom == TargetIdiom.Tablet)
{
fontSize = "320%"; // > 100% shows larger than previous
}
string injectCustomFontScript = @"
let style = document.createElement('style');
style.innerHTML = `
@font-face {
font-family: 'CustomFont';
src: url('Poppins-Light') format('truetype');
}
body, p, h1, h2, h3, h5, h6 {
font-family: 'CustomFont', sans-serif !important;
color: #313131 !important;
}
h4 {
font-family: 'CustomFont', sans-serif !important;
color: #679E18 !important;
}
`;
document.head.appendChild(style);
";
string stringsss = String.Format(@"document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '{0}'", fontSize);
WKJavascriptEvaluationResult handler = (NSObject result, NSError err) =>
{
if (err != null)
{
System.Console.WriteLine(err);
}
if (result != null)
{
System.Console.WriteLine(result);
}
};
webView.EvaluateJavaScript(stringsss, handler);
webView.EvaluateJavaScript(injectCustomFontScript, handler);
}
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == "Url")
{
string finalHtml = Element.Url.Replace("width=\"640\"", "width=\"1000\"");
Control.LoadHtmlString(finalHtml, null);
}
}
}
XAML Code:
<local:MyWebView
x:Name="ios_web_view"
Margin="0,5,0,0"
Grid.Row="0"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand">
<local:MyWebView.HeightRequest>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>10000</OnIdiom.Phone>
<OnIdiom.Tablet>15000</OnIdiom.Tablet>
<OnIdiom.Desktop>10000</OnIdiom.Desktop>
</OnIdiom>
</local:MyWebView.HeightRequest>
</local:MyWebView>
I want the WebView height to automatically adjust based on the HTML content’s height instead of setting a fixed HeightRequest. Since the content changes daily, I cannot hardcode a specific height.
Complete Layout:
<ContentPage
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
x:Name="ContentPage"
BackgroundColor="#F5F5F5"
xmlns:ffimageloading="clr-namespace:FFImageLoading.Maui;assembly=FFImageLoading.Maui"
xmlns:fftransformations="clr-namespace:FFImageLoading.Transformations;assembly=FFImageLoading.Maui"
xmlns:local="clr-namespace:Renderer"
x:Class="Views.DailyReadingPage">
<ContentPage.Behaviors>
<toolkit:StatusBarBehavior StatusBarColor="#0279B5" StatusBarStyle="DarkContent" />
</ContentPage.Behaviors>
<ContentPage.Content>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="8*" />
<RowDefinition Height="82*" />
<RowDefinition Height="10*" />
</Grid.RowDefinitions>
<!--Header Layout-->
<StackLayout
Grid.Row="0"
BackgroundColor="#0191da"
Orientation="Vertical"
VerticalOptions="FillAndExpand"
HorizontalOptions="FillAndExpand">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="{OnIdiom Phone=60, Tablet=90, Desktop=60}" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1.5*"/>
<ColumnDefinition Width="7*"/>
<ColumnDefinition Width="1.5*"/>
</Grid.ColumnDefinitions>
//Header Layout
</Grid>
</StackLayout>
<!--main Content View-->
<Grid
Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid
Grid.Row="0">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid
Grid.Row="0"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand"
Padding="5">
<Grid.RowDefinitions>
<RowDefinition Height="18*" />
<RowDefinition Height="82*" />
<!--<RowDefinition Height="8*" />-->
</Grid.RowDefinitions>
<StackLayout Grid.Row="0" Orientation="Vertical"
Padding="0">
<!--Title content>
</StackLayout>
<Frame
Grid.Row="1"
Margin="0,10,0,0"
Padding="0"
CornerRadius="{OnIdiom Phone=20, Tablet=30, Desktop=20}"
VerticalOptions="FillAndExpand"
x:Name="ios_layout">
<ScrollView
Orientation="Vertical"
VerticalOptions="FillAndExpand">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<!-- Background image -->
<Image Aspect="Fill" HorizontalOptions="FillAndExpand" Grid.Row="0" Source="ic_daily_reading_new_bg_xx.png"/>
<!-- Main content -->
<local:MyWebView
x:Name="ios_web_view"
Margin="0,5,0,0"
Grid.Row="0"
HorizontalOptions="FillAndExpand"
VerticalOptions="FillAndExpand">
<local:MyWebView.HeightRequest>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>10000</OnIdiom.Phone>
<OnIdiom.Tablet>15000</OnIdiom.Tablet>
<OnIdiom.Desktop>10000</OnIdiom.Desktop>
</OnIdiom>
</local:MyWebView.HeightRequest>
</local:MyWebView>
<!-- Audio frame -->
<Frame
x:Name="ios_audio_frame"
Grid.Row="1"
BackgroundColor="#666664"
Padding="0"
CornerRadius="{OnIdiom Phone=30, Tablet=45, Desktop=30}"
Margin="0,0,0,15"
HorizontalOptions="CenterAndExpand"
VerticalOptions="EndAndExpand">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="25*" />
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="25*" />
</Grid.ColumnDefinitions>
//Audio Layout
</Grid>
<Frame.WidthRequest>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>370</OnIdiom.Phone>
<OnIdiom.Tablet>950</OnIdiom.Tablet>
<OnIdiom.Desktop>370</OnIdiom.Desktop>
</OnIdiom>
</Frame.WidthRequest>
<Frame.HeightRequest>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>64</OnIdiom.Phone>
<OnIdiom.Tablet>96</OnIdiom.Tablet>
<OnIdiom.Desktop>64</OnIdiom.Desktop>
</OnIdiom>
</Frame.HeightRequest>
</Frame>
<!-- Frame footer image -->
<ffimageloading:CachedImage
Grid.Row="2"
Aspect="AspectFit"
HorizontalOptions="Fill"
VerticalOptions="End"
Source="ic_jesus_xx.png">
</ffimageloading:CachedImage>
</Grid>
</ScrollView>
</Frame>
</Grid>
<Grid.GestureRecognizers>
<PinchGestureRecognizer PinchUpdated="OnPinchUpdated"/>
</Grid.GestureRecognizers>
</Grid>
</Grid>
<!--Footer Layout-->
<Grid
Grid.Row="2"
VerticalOptions="Center"
BackgroundColor="White">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="25*" />
<ColumnDefinition Width="25*" />
<ColumnDefinition Width="25*" />
<ColumnDefinition Width="25*" />
</Grid.ColumnDefinitions>
//Footer Layout
<Grid.HeightRequest>
<OnIdiom x:TypeArguments="x:Double">
<OnIdiom.Phone>60</OnIdiom.Phone>
<OnIdiom.Tablet>90</OnIdiom.Tablet>
<OnIdiom.Desktop>60</OnIdiom.Desktop>
</OnIdiom>
</Grid.HeightRequest>
</Grid>
</Grid>
</ContentPage.Content>
You can customize the MyNavigationDelegate to calculate the WebView Height based on WKWebView.ScrollView. You may try the following way to adjust the height,
In the MyNavigationDelegate method, add a Constructor and set the value for myWebViewRenderer. Then in the DidFinishNavigation method, set the WebView's HeightRequest.
public class MyNavigationDelegate : WKNavigationDelegate
{
MyWebViewRenderer myWebViewRenderer;
public MyNavigationDelegate(MyWebViewRenderer webViewRenderer)
{
myWebViewRenderer = webViewRenderer;
}
public async override void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
{
......
//add the following code
var wv = myWebViewRenderer.Element as MyWebView;
if (webView != null)
{
if (webView.ScrollView != null && webView.ScrollView.ContentSize != null)
{
//wait for the content to be rendererd
await Task.Delay(200);
wv.HeightRequest = (double)webView.ScrollView.ContentSize.Height;
}
}
}
And in OnElementChanged, set
if (Control == null)
{
....
_wkWebView.NavigationDelegate = new MyNavigationDelegate(this);
SetNativeControl(_wkWebView);
}
Hope it helps!