Call Java function from JavaScript over Android WebView

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I don’t think this is the best solution to get the javascript to execute java code. See here:

If you want to expose native code to the HTML to be callable via javascript, do the following around your web view declaration:

JavaScriptInterface jsInterface = new JavaScriptInterface(this);
webView.getSettings().setJavaScriptEnabled(true);
webView.addJavascriptInterface(jsInterface, "JSInterface");

Declare the class JavaScriptInterface:

public class JavaScriptInterface {
    private Activity activity;

    public JavaScriptInterface(Activity activity) {
        this.activity = activity;
    }

    @JavascriptInterface
    public void startVideo(String videoAddress){
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(Uri.parse(videoAddress), "video/3gpp"); 
        activity.startActivity(intent);
    }
}

I am declaring a single function for playing a video, but you can do whatever you want.

Finally you call this in the WebView contents via simple javascript call:

<video width="320" height="240" controls="controls" poster="poster.gif"
       onclick="window.JSInterface.startVideo('file:///sdcard/test.3gp');" >
   Your browser does not support the video tag.
</video>

The example is taken from another answer of mine, about playing videos, but should be explaining enough.

EDIT As per @CedricSoubrie’s comment: if the target version of the application is set to 17 or higher you need to add annotation @JavascriptInterface above each method you want to export to the web view.

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