1page.title=Using WebViews 2@jd:body 3 4<p>A small application called <a title="WebViewDemo" 5href="http://code.google.com/p/apps-for-android/source/browse/#svn/trunk/Samples 6/WebViewDemo">WebViewDemo</a> shows how you can add web content to your 7application. You can find it in the <a title="apps-for-android" 8href="http://code.google.com/p/apps-for-android/">apps-for-android</a> project. 9This application demonstrates how you can embed a {@link android.webkit.WebView} 10into an activity and also how you can have two way communication between your 11application and the web content. </p> 12 13<p>A 14WebView uses the same rendering and JavaScript engine as the browser, 15but it runs under the control of your application. The WebView can be 16full screen or you can mix it with other Views. The content for your 17WebView can come from anywhere. The WebView can download content from 18the web, or it can come from local files stored in your assets 19directory. The content can even be dynamically generated by your 20application code. For this example, the HTML comes from a local file 21called <a title="demo.html" href="http://code.google.com/p/apps-for-android/source/browse/trunk/Samples/WebViewDemo/assets/demo.html">demo.html</a>.</p> 22 23<p>This application does not do very much: when you click on the 24android, he raises his arm.</p> 25 26<div style="text-align: center;"><img style="width: 322px; height: 482px;" src="images/webview.png"></div> 27 28<p>This 29could, of course, easily be accomplished with a little bit of 30JavaScript. Instead, though, WebViewDemo takes a slightly more 31complicated path to illustrate two very powerful features of WebView.</p> 32 33<p>First, 34JavaScript running inside the WebView can call out to code in your 35Activity. You can use this to have your JavaScript trigger actions like 36starting a new activity, or it can be used to fetch data from a 37database or {@link android.content.ContentProvider}. The API for this 38is very simple: just call the 39{@link android.webkit.WebView#addJavascriptInterface(java.lang.Object, java.lang.String) addJavascriptInterface()} 40method on your WebView. You pass an object whose methods you want to 41expose to JavaScript and the name to use when making calls. You can see 42the exact syntax in <a title="WebViewDemo.java" 43href="http://code.google.com/p/apps-for-android/source/browse/trunk/Samples/ 44WebViewDemo/src/com/google/android/webviewdemo/WebViewDemo.java">WebViewDemo. 45java</a>. Here we are making our DemoJavascriptInterface object available to 46JavaScript where it will be called "window.demo".</p> 47 48<p>Second, your Activity can invoke JavaScript methods. All you have to do 49is call the {@link android.webkit.WebView#loadUrl(java.lang.String) loadUrl} 50method with the appropriate JavaScript call:</p> 51 52<p><code style="padding-left: 25px;">mWebView.loadUrl("javascript:wave()");</code></p> 53 54<p>Our <a title="WebViewDemo" 55href="http://code.google.com/p/apps-for-android/source/browse/#svn/trunk/Samples 56/WebViewDemo">WebViewDemo</a> uses both techniques: when you click on the 57android, it calls out to the activity, which then turns around and calls back 58into the JavaScript. WebViews are very powerful, and they may be a valuable tool 59to help you build your application – especially if you already have a lot of 60HTML content. As it happens, we've used exactly this approach in some of the 61applications we've written.</p> 62
