I wanted to know if there is any way that I can call a JavaScript function from native Android Activity.
I came across:
webView.loadUrl("javascript:hello()");
But it did not work for me.
Also, how will Android know in which html page does this JavaScript function reside?
Android can only call the javascript method if an html page is currently loaded in webView
webView.loadUrl("javascript:hello()");
will call hello method writen in the html page only if the page containing this method is currently loaded in the webview control
first call
webview.loadUrl("Your html page url");
then call
webView.loadUrl("javascript:hello()");
In case anyone has any issues with this like I did, you need to call your javascript function after the page has finished loading otherwise the javascript won't be called:
webviewer.loadUrl("file:///android_asset/mypage.html");
webviewer.setWebViewClient(new WebViewClient() {
public void onPageFinished(WebView view, String url)
{
webviewer.loadUrl("javascript:hello()");
}
});
Before Using JavaScript, first you have to check Javascript is enabled or not in your application using "getJavaScriptEnabled () " (Its default FALSE). And loadUrl() method only used to load the current page only. Its does not do anything related to JavaScript.
EXAMPLE:
Setting up WebView
//initialization of webview
webView = (WebView) findViewById(R.id.webView);
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true);
Loading HTML in WebView
webView.loadUrl("file:///android_asset/testhtml.html");
Setting WebChromeClient to webView
webView.setWebChromeClient(new MyJavaScriptChromeClient());
The MyJavaScriptChromeClient class Here we have to override onJsAlert() method to handle JavaScript Alert Function.
private class MyJavaScriptChromeClient extends WebChromeClient {
@Override
public boolean onJsAlert(WebView view, String url, String message,final JsResult result) {
//handle Alert event, here we are showing AlertDialog
new AlertDialog.Builder(MainWebViewActivity.this)
.setTitle("JavaScript Alert !")
.setMessage(message)
.setPositiveButton(android.R.string.ok,
new AlertDialog.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// do your stuff
result.confirm();
}
}).setCancelable(false).create().show();
return true;
}
}
My Html File : testhtml.html :
<html>
<body >
<div onclick="alert('hello')"> Click Me !! </div>
</body>
</html>
How it Works ? When the text "Click Me !!" on the WebView is clicked, The android function onJsAlert(WebView view, String url, String message,final JsResult result) is called. The parameter to alert is copied to message parameter of onJsAlert function. And rest of the handling is done there. Here we are displaying a AlertDialog .