Android calling JavaScript functions in WebView with API <= 18

Question

This question isn't new here, but still I cannot get it where I go wrong. I just want to evaluate some javascript.

My simple code looks like:

WebView wv = new WebView(context);
WebSettings settings = wv.getSettings();
settings.setJavaScriptEnabled(true);

JavaBridgeToJS bridgeToJS = new JavaBridgeToJS();
wv.addJavascriptInterface(bridgeToJS, "javaCallback");

String src = "javascript: var result= 3 + 3; window.javaCallback.resultOfAdd(result)";

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
        Log.d(TAG, "Newer than JellyBean.");
        ValueCallback<String> result = new ValueCallback<String>() {
            @Override
            public void onReceiveValue(String value) {
                Log.d(TAG, "Got in onReceiveValue: " + value);
            }
        };
        wv.evaluateJavascript(src, result);
    }else {
        Log.d(TAG, "Older than Kitkat");
        wv.loadUrl(src);
    }

and

public class JavaBridgeToJS {
    @JavascriptInterface
    public void resultOfAdd(String result) {
        Log.d(TAG, "Here is: " + result);
    }
}

It is working good for API 19+, even without if with checking of version (I mean that it works with loadUrl as well as with evaluateJavascript)

But when I try API 18, the callback in java is not called. I have looked around (remove line break, or quotes missing (possibly infected, watched on phone), and so on...)

So far I have no luck. Any idea?

EDIT

Well, I have added code for handling errors inside of JS in case, that I have missed something.

wv.setWebChromeClient(new CustomWebChromeClient());

as

public class CustomWebChromeClient extends WebChromeClient {
    private CustomWebChromeClient() {
        super();
    }

    @Override
    public boolean onConsoleMessage(ConsoleMessage consoleMessage) {
        UILog.d(TAG, consoleMessage.message());
        return super.onConsoleMessage(consoleMessage);
    }
}

and I was suprised with:

E/dalvikvm: Could not find class 'android.webkit.PermissionRequest', referenced from method com.example.WebViewDoll$CustomWebChromeClient.access$super
VFY: unable to resolve check-cast 1896 (Landroid/webkit/PermissionRequest;) in Lcom/example/WebViewDoll$CustomWebChromeClient;
E/dalvikvm: Could not find class 'android.webkit.WebChromeClient$FileChooserParams', referenced from method com.example.WebViewDoll$CustomWebChromeClient.access$super
VFY: unable to resolve check-cast 1899 (Landroid/webkit/WebChromeClient$FileChooserParams;) in Lcom/example/WebViewDoll$CustomWebChromeClient;
E/dalvikvm: Could not find class 'android.webkit.PermissionRequest', referenced from method com.example.WebViewDoll$CustomWebChromeClient.access$super

D/WebViewDoll: Uncaught TypeError: Cannot call method 'resultOfAdd' of undefined
E/Web Console: Uncaught TypeError: Cannot call method 'resultOfAdd' of undefined at null:1

**UPDATE** I have made new project, just in case, but still nothing. I suppose this should work [github repo](https://github.com/ThinkDeeper/webview_api18) — ThinkDeep, Jun 01 '16 at 07:07

score 0 · Accepted Answer · edited May 23 '17 at 10:28

I did not find an answer why this is not working, but with help of this using js in webview I was able to make a workaround ...

I have to inject my js into a html page. So my wrapper arround js looks like:

String src = "<html><head><script type=\"text/javascript\">" +
            "function myFunction()" +
            "{" +
            "    javaCallback.resultOfAdd(3+3);" +
            "}" +
            "</script></head><body onload=\"myFunction()\"/>" +
            "</html>";

and instead of wv.loadUrl I have used:

wv.loadData(src, "text/html", "UTF-8");

This combination have same result as needed.

Android calling JavaScript functions in WebView with API <= 18

1 Answers1