Android Tutorial

Android Tutorial 389

The sample.html file defines four JavaScript functions and displays

the form shown within the WebView:

 The doToast() function calls into the Android application using the jse

object defined earlier with the call to the addJavaScriptInterface() method.

The add JavaScriptInterface() method, for all practical intents and

purposes, can be treated literally as the JavaScriptExtensions class as if

that class had been written in JavaScript. If the doToast() function had

returned a value, we could assign it to a variable here.

 The doConsoleLog() function writes into the JavaScript console log, which

is picked up by the onConsoleMessage() callback of the

WebChromeClient.

 The doAlert() function illustrates how alerts work within the WebView

control by launching a dialog. If you want to override what the alert looks

like, you can override the WebChromeClient.onJSAlert() method.

 The doSetFormText() function illustrates how native Java code can

communicate back through the JavaScript interface and provide data to

the web application.

Finally, to demonstrate making a call from Java back to JavaScript,

you need to define the click handler for the Button control within

your Activity class. Here, the onClick handler, called setHTMLText(),

executes some JavaScript on the currently loaded page by calling a

JavaScript function called doSetFormText(), which we defined

earlier in the web page. Here is an implementation of the

setHTMLText() method:

public void setHTMLText(View view) {
WebView wv = (WebView) findViewById(R.id.html_viewer);
wv.loadUrl(“javascript:doSetFormText(„Java->JS call‟);”);
}