Compose WebView Part 6 | Bind JavaScript code to Android code

WebView With Jetpack Compose in Android Studio | Kotlin | Jetpack Compose | Android Tutorials | Convert Your Website into an App | Build web apps in WebView .

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#webview
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If you want to deliver a web application (or just a web page) as a part of a client application, you can do it using WebView. The WebView class is an extension of Android's View class that allows you to display web pages as a part of your activity layout. It does not include any features of a fully developed web browser, such as navigation controls or an address bar. All that WebView does, by default, is show a web page.

A common scenario in which using WebView is helpful is when you want to provide information in your app that you might need to update, such as an end-user agreement or a user guide. Within your Android app, you can create an Activity that contains a WebView, then use that to display your document that's hosted online.

Another scenario in which WebView can help is if your app provides data to the user that always requires an Internet connection to retrieve data, such as email. In this case, you might find that it's easier to build a WebView in your Android app that shows a web page with all the user data, rather than performing a network request, then parsing the data and rendering it in an Android layout. Instead, you can design a web page that's tailored for Android devices and then implement a WebView in your Android app that loads the web page.

This document shows you how to get started with WebView and how to do some additional things, such as handle page navigation and bind JavaScript from your web page to client-side code in your Android app.
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Use JavaScript in WebView
If the web page you plan to load in your WebView uses JavaScript, you must enable JavaScript for your WebView. Once JavaScript is enabled, you can also create interfaces between your app code and your JavaScript code.

Enable JavaScript
JavaScript is disabled in a WebView by default. You can enable it through the WebSettings attached to your WebView.You can retrieve WebSettings with getSettings(), then enable JavaScript with setJavaScriptEnabled().

When developing a web application that's designed specifically for the WebView in your Android app, you can create interfaces between your JavaScript code and client-side Android code. For example, your JavaScript code can call a method in your Android code to display a Dialog, instead of using JavaScript's alert() function.

To bind a new interface between your JavaScript and Android code, call addJavascriptInterface(), passing it a class instance to bind to your JavaScript and an interface name that your JavaScript can call to access the class.

You can bind this class to the JavaScript that runs in your WebView with addJavascriptInterface() and name the interface Android. For example:

..

This creates an interface called Android for JavaScript running in the WebView. At this point, your web application has access to the WebAppInterface class. For example, here's some HTML and JavaScript that creates a toast message using the new interface when the user clicks a button.

[mikelantzelo]

Thank you.Can i ask a question? How to access evaluateJavascript outside webview lamda?