Execute JavaScript methods from native code

You can execute JavaScript in an in-app message from native code by completing the following steps:

Implement and assign a `MessagingDelegate`

To register a JavaScript event handler with a Message object, you will first need to implement and set a MessagingDelegate.

For more detailed instructions on implementing and using a MessagingDelegate, please read the tutorial on using MessagingDelegate.

Obtain a reference to the web view

In the shouldShowMessage function of the MessagingDelegate, get a reference to the web view used by the message.

Android

On Android, the web view is represented as WebView.

Java

@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  
  ...
}
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@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  
  ...
}

iOS

On iOS, the web view is represented as WKWebView.

Swift

func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    let messageWebView = message?.view as? WKWebView

    ...
}
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func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    let messageWebView = message?.view as? WKWebView

    ...
}

On Android, the web view is represented as WebView.

Java

@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  
  ...
}
Copied to your clipboard
@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  
  ...
}

On iOS, the web view is represented as WKWebView.

Swift

func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    let messageWebView = message?.view as? WKWebView

    ...
}
Copied to your clipboard
func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    let messageWebView = message?.view as? WKWebView

    ...
}

Call the JavaScript method

Android

With a reference to the WebView, the instance method public void evaluateJavascript(@NonNull String script, @Nullable ValueCallback<String> resultCallback) can now be leveraged to call a JavaScript method.

Further details of this API are explained in the Android documentation - the example below is provided for the purpose of demonstration:

Java

@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  // webview operations must be run on the ui thread
  webView.post(new Runnable() {
    @Override
    public void run() {
      webView.evaluateJavascript("startTimer()", new ValueCallback<String>() {
        @Override
        public void onReceiveValue(String s) {
          // do something with the content
        }
      });
    }
  });
  
  ...
}
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@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  // webview operations must be run on the ui thread
  webView.post(new Runnable() {
    @Override
    public void run() {
      webView.evaluateJavascript("startTimer()", new ValueCallback<String>() {
        @Override
        public void onReceiveValue(String s) {
          // do something with the content
        }
      });
    }
  });
  
  ...
}

iOS

With a reference to the WKWebView, the instance method evaluateJavaScript(_:completionHandler:) can now be leveraged to call a JavaScript method.

Further details of this API are explained in the Apple documentation - the example below is provided for the purpose of demonstration:

Swift

func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    // the `shouldShowMessage` delegate method is called on a background thread.
    // need to dispatch code that uses the webview back to the main thread.
    DispatchQueue.main.async {
        let messageWebView = message?.view as? WKWebView

        messageWebView?.evaluateJavaScript("startTimer();") { result, error in
            if error != nil {
                // handle error
                return
            }

            if result != nil {
                // do something with the result
            }
        }                
    }

    ...
}
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func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    // the `shouldShowMessage` delegate method is called on a background thread.
    // need to dispatch code that uses the webview back to the main thread.
    DispatchQueue.main.async {
        let messageWebView = message?.view as? WKWebView

        messageWebView?.evaluateJavaScript("startTimer();") { result, error in
            if error != nil {
                // handle error
                return
            }

            if result != nil {
                // do something with the result
            }
        }                
    }

    ...
}

Further details of this API are explained in the Android documentation - the example below is provided for the purpose of demonstration:

Java

@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  // webview operations must be run on the ui thread
  webView.post(new Runnable() {
    @Override
    public void run() {
      webView.evaluateJavascript("startTimer()", new ValueCallback<String>() {
        @Override
        public void onReceiveValue(String s) {
          // do something with the content
        }
      });
    }
  });
  
  ...
}
Copied to your clipboard
@Override
public boolean shouldShowMessage(FullscreenMessage fullscreenMessage) {
  // access to the whole message from the parent
  Message message = (Message) fullscreenMessage.getParent();
      
  WebView webView = message.getWebView();
  // webview operations must be run on the ui thread
  webView.post(new Runnable() {
    @Override
    public void run() {
      webView.evaluateJavascript("startTimer()", new ValueCallback<String>() {
        @Override
        public void onReceiveValue(String s) {
          // do something with the content
        }
      });
    }
  });
  
  ...
}

With a reference to the WKWebView, the instance method evaluateJavaScript(_:completionHandler:) can now be leveraged to call a JavaScript method.

Further details of this API are explained in the Apple documentation - the example below is provided for the purpose of demonstration:

Swift

func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    // the `shouldShowMessage` delegate method is called on a background thread.
    // need to dispatch code that uses the webview back to the main thread.
    DispatchQueue.main.async {
        let messageWebView = message?.view as? WKWebView

        messageWebView?.evaluateJavaScript("startTimer();") { result, error in
            if error != nil {
                // handle error
                return
            }

            if result != nil {
                // do something with the result
            }
        }                
    }

    ...
}
Copied to your clipboard
func shouldShowMessage(message: Showable) -> Bool {
    // access to the whole message from the parent
    let fullscreenMessage = message as? FullscreenMessage
    let message = fullscreenMessage?.parent

    // the `shouldShowMessage` delegate method is called on a background thread.
    // need to dispatch code that uses the webview back to the main thread.
    DispatchQueue.main.async {
        let messageWebView = message?.view as? WKWebView

        messageWebView?.evaluateJavaScript("startTimer();") { result, error in
            if error != nil {
                // handle error
                return
            }

            if result != nil {
                // do something with the result
            }
        }                
    }

    ...
}

Examples

The test apps in this repository demonstrate executing JavaScript code from an in-app message's webview:

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Last updated 4/4/2024

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Execute JavaScript methods from native code

Implement and assign a MessagingDelegate.css-83mclq{margin-left:var(--spectrum-global-dimension-size-100);}

Obtain a reference to the web view

Java.css-jmmyhj{margin-left:var(--spectrum-global-dimension-size-50);}

Swift

Java

Swift

Call the JavaScript method

Java

Swift

Java

Swift

Examples

Implement and assign a `MessagingDelegate`

Java