WIP

BookAStar/BookAStar.Droid/MarkdownViewRenderer.cs

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+
+using BookAStar.Views;
+using Android.Webkit;
+using Xamarin.Forms.Platform.Android;
+using BookAStar.Droid;
+using System;
+using Java.Interop;
+
+[assembly: Xamarin.Forms.ExportRenderer(typeof(MarkdownView), typeof(MarkdownViewRenderer))]
+namespace BookAStar.Droid
+{
+    public class JSBridge : Java.Lang.Object
+    {
+        readonly WeakReference<MarkdownViewRenderer> hybridWebViewRenderer;
+
+        public JSBridge(MarkdownViewRenderer hybridRenderer)
+        {
+            hybridWebViewRenderer = new WeakReference<MarkdownViewRenderer>(hybridRenderer);
+        }
+
+        [JavascriptInterface]
+        [Export("invokeAction")]
+        public void InvokeAction(string data)
+        {
+            MarkdownViewRenderer hybridRenderer;
+
+            if (hybridWebViewRenderer != null && hybridWebViewRenderer.TryGetTarget(out hybridRenderer))
+            {
+                hybridRenderer.Element.Markdown=data;
+            }
+        }
+    }
+    public class MarkdownViewRenderer : ViewRenderer<MarkdownView, WebView>
+    {
+        private WebView editorView;
+        private MarkdownEditor editorTemplate = new MarkdownEditor();
+        private MarkdownDeep.Markdown markdown = new MarkdownDeep.Markdown();
+        const string JavaScriptFunction = "function invokeCSharpAction(data){jsBridge.invokeAction(data);}";
+
+        private void SetMDEditorText(string text)
+        {
+            editorTemplate.Model = (text == null) ? null : markdown.Transform(text);
+            var html = editorTemplate.GenerateString();
+            editorView.LoadDataWithBaseURL("file:///android_asset/",
+            html, "text/html", "utf-8", null);
+        }
+
+        protected override void OnElementChanged(ElementChangedEventArgs<MarkdownView> e)
+        {
+            base.OnElementChanged(e);
+            if (Control == null)
+            {
+                editorView = new WebView(Context);
+                editorView.Settings.BuiltInZoomControls = true;
+                editorView.Settings.JavaScriptEnabled = true;
+                editorView.Settings.LoadsImagesAutomatically = true;
+                editorView.Settings.SetAppCacheEnabled(true);
+                editorView.Settings.AllowContentAccess = true;
+                editorView.Settings.AllowFileAccess = true;
+                editorView.Settings.AllowFileAccessFromFileURLs = true;
+                editorView.Settings.AllowUniversalAccessFromFileURLs = true;
+                editorView.Settings.BlockNetworkImage = false;
+                editorView.Settings.BlockNetworkLoads = false;
+                editorView.Settings.DomStorageEnabled = true;
+              //  editorView.SetMinimumHeight(300);
+                SetNativeControl(editorView);
+            }
+            if (e.OldElement != null)
+            {
+                // Unsubscribe
+            }
+            if (e.NewElement != null)
+            {
+                // Subscribe
+                var viewclient = new MarkdownWebViewClient(
+                md => { e.NewElement.Markdown = md; });
+                editorView.SetWebViewClient(viewclient);
+                Control.AddJavascriptInterface(new JSBridge(this), "jsBridge");
+                SetMDEditorText(e.NewElement.Markdown);
+                InjectJS(JavaScriptFunction);
+            }
+        }
+        
+
+        void InjectJS(string script)
+        {
+            if (Control != null)
+            {
+                Control.LoadUrl(string.Format("javascript: {0}", script));
+            }
+        }
+
+    }
+}