How to get a callback from a custom renderer in xamarin forms - xamarin

Question

I Have a custom hybridWebView for android and ios to load the URL. What I required is to pass a callback to the content page once the URL has completed the loading. Code as below, help would much appreciate.
Content Page
public partial class ConveyancingLeadPage : ContentPage
{
DashboardViewModel viewmodel;
StorageService storage = new StorageService();
public ConveyancingLeadPage()
{
InitializeComponent();
GetUserAvatar();
}
protected async override void OnAppearing()
{
// I need the callback to be execute here
customView.weblink = viewmodel.BrokerData.config.conveyancing.listing_webview;
}
}
Android HybridView
[assembly: ExportRenderer(typeof(HCHybridWebview), typeof(HCHybridWebviewRendererAndroid))]
namespace HashChing.Droid.CustomRenderers
{
public class HCHybridWebviewRendererAndroid : ViewRenderer<HCHybridWebview, Android.Webkit.WebView>
{
Context _context;
public HCHybridWebviewRendererAndroid(Context context) : base(context)
{
_context = context;
}
protected override void OnElementChanged(ElementChangedEventArgs<HCHybridWebview> e)
{
base.OnElementChanged(e);
const string JavascriptFunction = "function invokeCSharpAction(data){jsBridge.invokeAction(data);}";
if (Control == null)
{
//Do something
if (e.NewElement != null)
{
//Load URL
Control.AddJavascriptInterface(new JSBridge(this), "jsBridge");
var hybridWebView = e.NewElement as HCHybridWebview;
if (hybridWebView != null)
{
hybridWebView.RefreshView += LoadUrl;
}
}
Load URL
public void LoadUrl(object sender, EventArgs e)
{
Control.LoadUrl(webView.weblink, headers);
}
Once the URL been loaded it will navigate to this method in the same class, and this is where I want to pass a callback TO my content page once the loading is completed inside the "OnPageFinished" method. Help would much appreciate.
public class JavascriptWebViewClient : WebViewClient
{
string _javascript;
public JavascriptWebViewClient(string javascript)
{
_javascript = javascript;
}
public override void OnPageFinished(Android.Webkit.WebView view, string url)
{
base.OnPageFinished(view, url);
view.EvaluateJavascript(_javascript, null);
}
}

Answer 1

you could use MessagingCenter to send and get the callback:
in your ContentPage,for example Page1.xaml.cs
public Page1 ()
{
InitializeComponent ();
//here you could get the callback,and arg = "this is call back"
MessagingCenter.Subscribe<Page1,string>(this,"callback", (send, arg) =>
{
Console.WriteLine(arg);
});
}
then in your OnPageFinished method:
public override void OnPageFinished(Android.Webkit.WebView view, string url)
{
base.OnPageFinished(view, url);
view.EvaluateJavascript(_javascript, null);
//send the callback content,Parameters can be defined by yourself
MessagingCenter.Send<Page1,string>(new Page1(), "callback","this is call back");
}
more information：MessagingCenter

Answer 2

create your own event LoadCompleted in your customrender and invoke it from your custom class once load is finish.
And in your JavascriptWebViewClient class you can subscribe to that event and do whatever you want do do at that time.
in case you need it: Events in c#
public partial class ConveyancingLeadPage : ContentPage
{
protected async override void OnAppearing()
{
customView.weblink = viewmodel.BrokerData.config.conveyancing.listing_webview;
// I need the callback to be execute here
customView.LoadCompleted+=LoadCompleted;
}
}