1 page.title=Using WebViews 2 @jd:body 3 4 <p>A small application called <a title="WebViewDemo" 5 href="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 7 application. You can find it in the <a title="apps-for-android" 8 href="http://code.google.com/p/apps-for-android/">apps-for-android</a> project. 9 This application demonstrates how you can embed a {@link android.webkit.WebView} 10 into an activity and also how you can have two way communication between your 11 application and the web content. </p> 12 13 <p>A 14 WebView uses the same rendering and JavaScript engine as the browser, 15 but it runs under the control of your application. The WebView can be 16 full screen or you can mix it with other Views. The content for your 17 WebView can come from anywhere. The WebView can download content from 18 the web, or it can come from local files stored in your assets 19 directory. The content can even be dynamically generated by your 20 application code. For this example, the HTML comes from a local file 21 called <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 24 android, 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 29 could, of course, easily be accomplished with a little bit of 30 JavaScript. Instead, though, WebViewDemo takes a slightly more 31 complicated path to illustrate two very powerful features of WebView.</p> 32 33 <p>First, 34 JavaScript running inside the WebView can call out to code in your 35 Activity. You can use this to have your JavaScript trigger actions like 36 starting a new activity, or it can be used to fetch data from a 37 database or {@link android.content.ContentProvider}. The API for this 38 is very simple: just call the 39 {@link android.webkit.WebView#addJavascriptInterface(java.lang.Object, java.lang.String) addJavascriptInterface()} 40 method on your WebView. You pass an object whose methods you want to 41 expose to JavaScript and the name to use when making calls. You can see 42 the exact syntax in <a title="WebViewDemo.java" 43 href="http://code.google.com/p/apps-for-android/source/browse/trunk/Samples/ 44 WebViewDemo/src/com/google/android/webviewdemo/WebViewDemo.java">WebViewDemo. 45 java</a>. Here we are making our DemoJavascriptInterface object available to 46 JavaScript where it will be called "window.demo".</p> 47 48 <p>Second, your Activity can invoke JavaScript methods. All you have to do 49 is call the {@link android.webkit.WebView#loadUrl(java.lang.String) loadUrl} 50 method 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" 55 href="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 57 android, it calls out to the activity, which then turns around and calls back 58 into the JavaScript. WebViews are very powerful, and they may be a valuable tool 59 to help you build your application especially if you already have a lot of 60 HTML content. As it happens, we've used exactly this approach in some of the 61 applications we've written.</p> 62
