Webview cannot load javascript at onPageFinished

Question

I want my webview insert sort of javascript after a page has been loaded. However, the javascript I added has never been executed:( what can I do on this?

mWebView = findViewById(R.id.webview);
mWebView.getSettings().setDomStorageEnabled(true);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.setWebViewClient(new WebViewClient() {
        @Override
        public void onPageFinished (WebView view, String url) {
            super.onPageFinished(view, url);
            Log.d("WebClient", "onPageFinished");
            view.loadUrl("javascript:(function(){"+
                    "aTagElements=document.getElementsByTagName('a');" +
                    "randromElement=aTagElements[Math.floor(Math.random() * aTagElements.length)];"+
                    "clickEvent=document.createEvent('HTMLEvents');"+
                    "clickEvent.initEvent('click',true,true);"+
                    "randromElement.dispatchEvent(clickEvent);" +
                    "alert('event dispatched.');"+ //<---not called
                    "})()");
        }
});

Even if I comment out all the scripts except the alert line, still nothing happens.

Where is the url of the webpage you want to load – Manoj Perumarath Feb 18 '19 at 05:11 — Manoj Perumarath, Feb 18 '19 at 05:11
@ManojPerumarath whatever url, my code does not work. – Simon Leung Feb 18 '19 at 05:17 — Simon Leung, Feb 18 '19 at 05:17

ॐ Rakesh Kumar · Answer 1 · 2019-02-18T05:17:18.387

2

You will have to use like this on application side

mWebView .addJavascriptInterface(new WebAppInterface(this), "Android");

and will have to implement method on php side where actually this method will be trigger

public class WebAppInterface {
    Context mContext;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context c) {
        mContext = c;
    }

    /** Show a toast from the web page */
    @JavascriptInterface
    public void showToast(String toast) {
        Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show();
    }
}

on PHP Side implement like this

<input type="button" value="Say hello" onClick="showAndroidToast('Hello Android!')" />

<script type="text/javascript">
    function showAndroidToast(toast) {
        Android.showToast(toast);
    }
</script>

For a complete reference, you can go through on this link

Whenever you will click the button on webView then you will get a message

edited Feb 18 '19 at 05:17

answered Feb 18 '19 at 05:05

ॐ Rakesh Kumar

1,318
1
14
24

My code is to create a 'click' behavior in the loaded HTML, this example may not fit me. Thank you for your effort. – Simon Leung Feb 18 '19 at 05:43
@SimonLeung, https://stackoverflow.com/questions/32163517/run-javascript-code-in-webview?answertab=active#tab-top – ॐ Rakesh Kumar Feb 18 '19 at 05:57
@Simon Leung, What is the issue now you are getting? – ॐ Rakesh Kumar Feb 18 '19 at 06:13
Inserting javascript after the page is loaded. evaluateJavascript gives me the callback but the javascript does not run. – Simon Leung Feb 18 '19 at 06:18

score 1 · Accepted Answer · answered Feb 18 '19 at 05:20

1

Try using evaluvateJavascript, loadUrl will work only in old version.

webview.evaluateJavascript("(function() { "javascript:(function(){"+
                "aTagElements=document.getElementsByTagName('a');" +
                "randromElement=aTagElements[Math.floor(Math.random() * aTagElements.length)];"+
                "clickEvent=document.createEvent('HTMLEvents');"+
                "clickEvent.initEvent('click',true,true);"+
                "randromElement.dispatchEvent(clickEvent);" +
                "alert('event dispatched.');";

EvaluvateJavascript

answered Feb 18 '19 at 05:20

Manoj Perumarath

9,337
8
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it takes 2 parameters and the 2nd one is a value callback. I put a logging in the callback and it shows the log but the javascript (even the alert one) is not executed. – Simon Leung Feb 18 '19 at 05:50
did you try it only using alert? – Manoj Perumarath Feb 18 '19 at 06:27
1

I tried on a simple html made by myself and it works now! I grab up 2 things that mislead me. 1) users cannot see the generated click events occurred 2) alert function works in my simple html, perhaps the alert was blocked by other websites that I thought the script does not work. – Simon Leung Feb 18 '19 at 07:21

score 1 · Answer 3 · answered Feb 18 '19 at 06:33

1

You are mixing views. So change

super.onPageFinished(view, url);

To

super.onPageFinished(mWebView, url);

answered Feb 18 '19 at 06:33

statosdotcom

3,109
2
17
40

score 0 · Answer 4 · answered Feb 18 '19 at 04:51

Try the below solution may it works for you.

WebSettings webSettings = webView.getSettings();
webSettings.setDefaultTextEncodingName("utf-8");
webSettings.setJavaScriptEnabled(true);
webSettings.setDomStorageEnabled(true);
webSettings.setLoadWithOverviewMode(true);

Webview cannot load javascript at onPageFinished

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