我正在尝试在ItemTemplate中添加WebView控件并设置行的高度。我知道我无法使用webview控件滚动，因此我需要将高度设置为正确的大小以显示完整的html内容。我创建了一个IValueConverter类，该类可以返回所需的正确高度，但是要返回的高度值取决于内容的长度呢？
无论如何，我都可以加载Web视图并获得显示完整内容所需的高度，而我在writeline中获得的高度为-1？
XAML代码
<telerikListView:ListViewTemplateCell>
<Grid BackgroundColor="{StaticResource LightBlueColor}"
Padding="10">
<telerikPrimitives:RadBorder Padding="10"
HorizontalOptions="Fill"
BorderThickness="2"
BorderColor="{StaticResource DarkBlueColor}"
BackgroundColor="White">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="50" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<!--<RowDefinition Height="*"/>-->
<RowDefinition Height="{Binding AssetItem.Description, Converter={StaticResource DescriptionToHeightConverter}}" />
</Grid.RowDefinitions>
<!--<Grid Grid.Row="0" Grid.Column="0">
<HtmlLabelControl:HtmlLabel
Text="{Binding AssetItem.Description}"
HeightRequest="100"/>-->
<WebView HeightRequest="800" MinimumHeightRequest="300" HorizontalOptions="FillAndExpand">
<WebView.Source>
<HtmlWebViewSource Html="{Binding AssetItem.Description}"/>
</WebView.Source>
</WebView>
<!--</Grid>-->
<!--<WebView Grid.Column="0" Grid.Row="0" HeightRequest="200" HorizontalOptions="FillAndExpand">
<WebView.Source>
<HtmlWebViewSource Html="{Binding AssetItem.Description}"/>
</WebView.Source>
</WebView>-->
<!--<Label Text="{Binding AssetItem.Description}"
TextColor="{StaticResource GrayTextColor}"
Grid.Row="0"
Grid.Column="0"/>-->
<!--Star-->
<telerikPrimitives:RadPath
x:Name="path"
Grid.Row="0"
Grid.Column="1"
WidthRequest="40"
HeightRequest="35"
StrokeThickness="2"
VerticalOptions="Start"
Fill="{Binding AssetItem.IsBookmark, Converter={StaticResource FavFillColorConverter}}"
Stroke="#3e7dc5"
Geometry="{x:Static telerikInput:Geometries.Star}">
<telerikPrimitives:RadPath.GestureRecognizers>
<TapGestureRecognizer NumberOfTapsRequired="1" Tapped="BookmarkCommand" CommandParameter="{Binding AssetItem.AssetId}" />
</telerikPrimitives:RadPath.GestureRecognizers>
</telerikPrimitives:RadPath>
</Grid>
<!--</Grid>-->
</telerikPrimitives:RadBorder>
</Grid>
</telerikListView:ListViewTemplateCell>
CS转换器逻辑
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var description = value as string;
//WebView wv = new WebView();
//wv.Source = description;
HtmlWebViewSource HtmlSource = new HtmlWebViewSource();
HtmlSource.Html = description;
WebView webView = new WebView()
{
Source = HtmlSource
};
Debug.WriteLine($"Web View Height: {webView.Height}");
if (!string.IsNullOrEmpty(description))
{
if (description.Length == 300)
{
return 50;
}
}
return 300;
}
测试代码
HtmlWebViewSource HtmlSource = new HtmlWebViewSource();
HtmlSource.Html = "<html><body><div><h1>MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM</h1></div></body></html>";
WebView webView = new WebView()
{
Source = HtmlSource
};
string htmlheight = "";
Task.Run(async () => {
try
{
htmlheight = await webView.EvaluateJavaScriptAsync("document.body.scrollHeight");
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
});
//WebView_NavigatedAsync(webView);
Debug.WriteLine($"Web View Height: {htmlheight}");
答案 0 :(得分：0)
如果要获取html的高度，则可以使用“自定义渲染器”（Custom Renderer）来实现
表格
public MainPage()
{
InitializeComponent();
HtmlWebViewSource HtmlSource = new HtmlWebViewSource();
HtmlSource.Html = @"<html><body>
<h1>Xamarin.Forms</h1>
<p>Welcome to WebView.</p>
</body></html>";
Webview webView = new Webview()
{
WidthRequest = 100,
HeightRequest = 20,
Source =HtmlSource
};
MessagingCenter.Subscribe<Object, float>(this,"webview_loaded",(sender,value)=>{
Console.WriteLine(value); //value is the height of html
});
Content = new StackLayout
{
Children =
{
webView,
},
VerticalOptions = LayoutOptions.FillAndExpand,
HorizontalOptions=LayoutOptions.FillAndExpand
};
}
在iOS项目中
using Foundation;
using UIKit;
using CoreGraphics;
using xxx;
using xxx.iOS;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;
[assembly:ExportRenderer(typeof(WebView),typeof(MyWebViewRenderer))]
namespace App7.iOS
{
public class MyWebViewRenderer:WebViewRenderer,IUIWebViewDelegate
{
protected override void OnElementChanged(VisualElementChangedEventArgs e)
{
base.OnElementChanged(e);
if(NativeView!=null)
{
// WeakDelegate = this;
}
}
[Export("webViewDidFinishLoad:")]
public void LoadingFinished(UIWebView webView)
{
string htmlHeight = webView.EvaluateJavascript("document.body.scrollHeight");
float height = float.Parse(htmlHeight);
MessagingCenter.Send<System.Object, float>(this, "webview_loaded", height);
}
}
}
在Android中
using Android.Content;
using Android.Webkit;
using Android.Widget;
using xxx;
using xxx.Droid;
using Java.Lang;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
[assembly: ExportRenderer(typeof(Xamarin.Forms.WebView), typeof(MyWebViewRenderer))]
namespace xxx.Droid
{
public class MyWebViewRenderer:WebViewRenderer
{
public MyWebViewRenderer(Context context):base(context)
{
}
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
{
base.OnElementChanged(e);
if(Control!=null)
{
Android.Webkit.WebView webview =(Android.Webkit.WebView) Control;
WebSettings settings = webview.Settings;
settings.JavaScriptEnabled = true;
webview.SetWebViewClient(new JavascriptWebViewClient());
}
}
}
public class JavascriptWebViewClient : WebViewClient
{
public override void OnPageFinished(Android.Webkit.WebView view, string url)
{
base.OnPageFinished(view, url);
view.EvaluateJavascript("javascript:document.body.scrollHeight;", new EvaluateBack() );
}
}
class EvaluateBack : Java.Lang.Object, IValueCallback
{
public void OnReceiveValue(Java.Lang.Object value)
{
string htmlHeight = value.ToString();
float height = float.Parse(htmlHeight);
MessagingCenter.Send<System.Object, float>(this,"webview_loaded",height);
}
}
}
注意：在您的测试代码中，当html尚未完成加载时会调用该方法，因此结果为-1。