[英]How to call Navigation.PopAsync() from Javascript
我在Xamarin Forms內容中有一個Web視圖,我在其中使用純html div
,我想導航至div
onClick()
上的另一個頁面( Navigation.PopAsync
或Navigation.PushAsync
onClick()
,是否可以不實現任何渲染器或混合視圖?
您可以創建一個HybridWebView來實現您的功能。
HybridWebView.cs:
public class HybridWebView : View
{
Action<string> action;
public static readonly BindableProperty UriProperty = BindableProperty.Create (
propertyName: "Uri",
returnType: typeof(string),
declaringType: typeof(HybridWebView),
defaultValue: default(string));
public string Uri {
get { return (string)GetValue (UriProperty); }
set { SetValue (UriProperty, value); }
}
public void RegisterAction (Action<string> callback)
{
action = callback;
}
public void Cleanup ()
{
action = null;
}
public void InvokeAction (string data)
{
if (action == null || data == null) {
return;
}
action.Invoke (data);
}
}
在Xaml.cs中使用 :
<local:HybridWebView x:Name="hybridWebView" Uri="index.html" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" />
然后在Android中 ,創建HybridWebViewRenderer.cs
:
public class HybridWebViewRenderer : ViewRenderer<HybridWebView, Android.Webkit.WebView>
{
const string JavascriptFunction = "function invokeCSharpAction(data){jsBridge.invokeAction(data);}";
Context _context;
public HybridWebViewRenderer(Context context) : base(context)
{
_context = context;
}
protected override void OnElementChanged(ElementChangedEventArgs<HybridWebView> e)
{
base.OnElementChanged(e);
if (e.OldElement != null)
{
Control.RemoveJavascriptInterface("jsBridge");
var hybridWebView = e.OldElement as HybridWebView;
hybridWebView.Cleanup();
}
if (e.NewElement != null)
{
if (Control == null)
{
var webView = new Android.Webkit.WebView(_context);
webView.Settings.JavaScriptEnabled = true;
webView.SetWebViewClient(new JavascriptWebViewClient($"javascript: {JavascriptFunction}"));
SetNativeControl(webView);
}
Control.AddJavascriptInterface(new JSBridge(this), "jsBridge");
Control.LoadUrl($"file:///android_asset/Content/{Element.Uri}");
}
}
}
Renderer中的JavascriptWebViewClient.cs如下:
public class JavascriptWebViewClient : WebViewClient
{
string _javascript;
public JavascriptWebViewClient(string javascript)
{
_javascript = javascript;
}
public override void OnPageFinished(WebView view, string url)
{
base.OnPageFinished(view, url);
view.EvaluateJavascript(_javascript, null);
}
}
還需要JSBridge
處理JavaScript:
public class JSBridge : Java.Lang.Object
{
readonly WeakReference<HybridWebViewRenderer> hybridWebViewRenderer;
public JSBridge (HybridWebViewRenderer hybridRenderer)
{
hybridWebViewRenderer = new WeakReference <HybridWebViewRenderer> (hybridRenderer);
}
[JavascriptInterface]
[Export ("invokeAction")]
public void InvokeAction (string data)
{
HybridWebViewRenderer hybridRenderer;
if (hybridWebViewRenderer != null && hybridWebViewRenderer.TryGetTarget (out hybridRenderer))
{
hybridRenderer.Element.InvokeAction (data);
}
}
}
Okey, index.html
示例如下:
<html>
<body>
<script src="http://code.jquery.com/jquery-2.1.4.min.js"></script>
<h1>HybridWebView Test</h1>
<br/>
Enter name: <input type="text" id="name">
<br/>
<br/>
<button type="button" onclick="javascript:invokeCSCode($('#name').val());">Invoke C# Code</button>
<br/>
<p id="result">Result:</p>
<script type="text/javascript">
function log(str)
{
$('#result').text($('#result').text() + " " + str);
}
function invokeCSCode(data) {
try {
log("Sending Data:" + data);
invokeCSharpAction(data);
}
catch (err){
log(err);
}
}
</script>
</body>
</html>
運行后,視圖如下:
最后,我們從JavaScript調用函數的地方是ContenPage:
hybridWebView.RegisterAction ( data => { Navigation.PushModalAsync(new PageNext()); });
IOS HybridWebViewRenderer.cs
類如下:
public class HybridWebViewRenderer : ViewRenderer<HybridWebView, WKWebView>, IWKScriptMessageHandler
{
const string JavaScriptFunction = "function invokeCSharpAction(data){window.webkit.messageHandlers.invokeAction.postMessage(data);}";
WKUserContentController userController;
protected override void OnElementChanged (ElementChangedEventArgs<HybridWebView> e)
{
base.OnElementChanged (e);
if (e.OldElement != null) {
userController.RemoveAllUserScripts ();
userController.RemoveScriptMessageHandler ("invokeAction");
var hybridWebView = e.OldElement as HybridWebView;
hybridWebView.Cleanup ();
}
if (e.NewElement != null) {
if (Control == null)
{
userController = new WKUserContentController();
var script = new WKUserScript(new NSString(JavaScriptFunction), WKUserScriptInjectionTime.AtDocumentEnd, false);
userController.AddUserScript(script);
userController.AddScriptMessageHandler(this, "invokeAction");
var config = new WKWebViewConfiguration { UserContentController = userController };
var webView = new WKWebView(Frame, config);
SetNativeControl(webView);
}
string fileName = Path.Combine (NSBundle.MainBundle.BundlePath, string.Format ("Content/{0}", Element.Uri));
Control.LoadRequest (new NSUrlRequest (new NSUrl (fileName, false)));
}
}
public void DidReceiveScriptMessage (WKUserContentController userContentController, WKScriptMessage message)
{
Element.InvokeAction (message.Body.ToString ());
}
}
這里也有官方樣品供參考。
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