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| -rw-r--r-- | core/java/android/webkit/WebView.java | 123 |
1 files changed, 103 insertions, 20 deletions
diff --git a/core/java/android/webkit/WebView.java b/core/java/android/webkit/WebView.java index f921caa..863a6cd 100644 --- a/core/java/android/webkit/WebView.java +++ b/core/java/android/webkit/WebView.java @@ -109,36 +109,50 @@ import junit.framework.Assert; * {@link #getSettings() WebSettings}.{@link WebSettings#setBuiltInZoomControls(boolean)} * (introduced in API version 3). * <p>Note that, in order for your Activity to access the Internet and load web pages - * in a WebView, you must add the <var>INTERNET</var> permissions to your + * in a WebView, you must add the {@code INTERNET} permissions to your * Android Manifest file:</p> * <pre><uses-permission android:name="android.permission.INTERNET" /></pre> * - * <p>This must be a child of the <code><manifest></code> element.</p> + * <p>This must be a child of the <a + * href="{@docRoot}guide/topics/manifest/manifest-element.html">{@code <manifest>}</a> + * element.</p> * * <h3>Basic usage</h3> * * <p>By default, a WebView provides no browser-like widgets, does not - * enable JavaScript and errors will be ignored. If your goal is only + * enable JavaScript and web page errors are ignored. If your goal is only * to display some HTML as a part of your UI, this is probably fine; * the user won't need to interact with the web page beyond reading * it, and the web page won't need to interact with the user. If you - * actually want a fully blown web browser, then you probably want to - * invoke the Browser application with your URL rather than show it - * with a WebView. See {@link android.content.Intent} for more information.</p> + * actually want a full-blown web browser, then you probably want to + * invoke the Browser application with a URL Intent rather than show it + * with a WebView. For example: + * <pre> + * Uri uri = Uri.parse("http://www.example.com"); + * Intent intent = new Intent(Intent.ACTION_VIEW, uri); + * startActivity(intent); + * </pre> + * <p>See {@link android.content.Intent} for more information.</p> * + * <p>To provide a WebView in your own Activity, include a {@code <WebView>} in your layout, + * or set the entire Activity window as a WebView during {@link + * android.app.Activity#onCreate(Bundle) onCreate()}:</p> * <pre class="prettyprint"> * WebView webview = new WebView(this); * setContentView(webview); + * </pre> * + * <p>Then load the desired web page:</p> * // Simplest usage: note that an exception will NOT be thrown * // if there is an error loading this page (see below). * webview.loadUrl("http://slashdot.org/"); * - * // Of course you can also load from any string: + * // OR, you can also load from an HTML string: * String summary = "<html><body>You scored <b>192</b> points.</body></html>"; * webview.loadData(summary, "text/html", "utf-8"); * // ... although note that there are restrictions on what this HTML can do. - * // See the JavaDocs for loadData and loadDataWithBaseUrl for more info. + * // See the JavaDocs for {@link #loadData(String,String,String) loadData()} and {@link + * #loadDataWithBaseURL(String,String,String,String,String) loadDataWithBaseURL()} for more info. * </pre> * * <p>A WebView has several customization points where you can add your @@ -148,15 +162,20 @@ import junit.framework.Assert; * <li>Creating and setting a {@link android.webkit.WebChromeClient} subclass. * This class is called when something that might impact a * browser UI happens, for instance, progress updates and - * JavaScript alerts are sent here. + * JavaScript alerts are sent here (see <a + * href="{@docRoot}guide/developing/debug-tasks.html#DebuggingWebPages">Debugging Tasks</a>). * </li> * <li>Creating and setting a {@link android.webkit.WebViewClient} subclass. * It will be called when things happen that impact the * rendering of the content, eg, errors or form submissions. You - * can also intercept URL loading here.</li> - * <li>Via the {@link android.webkit.WebSettings} class, which contains - * miscellaneous configuration. </li> - * <li>With the {@link android.webkit.WebView#addJavascriptInterface} method. + * can also intercept URL loading here (via {@link + * android.webkit.WebViewClient#shouldOverrideUrlLoading(WebView,String) + * shouldOverrideUrlLoading()}).</li> + * <li>Modifying the {@link android.webkit.WebSettings}, such as + * enabling JavaScript with {@link android.webkit.WebSettings#setJavaScriptEnabled(boolean) + * setJavaScriptEnabled()}. </li> + * <li>Adding JavaScript-to-Java interfaces with the {@link + * android.webkit.WebView#addJavascriptInterface} method. * This lets you bind Java objects into the WebView so they can be * controlled from the web pages JavaScript.</li> * </ul> @@ -191,8 +210,8 @@ import junit.framework.Assert; * <h3>Cookie and window management</h3> * * <p>For obvious security reasons, your application has its own - * cache, cookie store etc - it does not share the Browser - * applications data. Cookies are managed on a separate thread, so + * cache, cookie store etc.—it does not share the Browser + * application's data. Cookies are managed on a separate thread, so * operations like index building don't block the UI * thread. Follow the instructions in {@link android.webkit.CookieSyncManager} * if you want to use cookies in your application. @@ -201,15 +220,79 @@ import junit.framework.Assert; * <p>By default, requests by the HTML to open new windows are * ignored. This is true whether they be opened by JavaScript or by * the target attribute on a link. You can customize your - * WebChromeClient to provide your own behaviour for opening multiple windows, + * {@link WebChromeClient} to provide your own behaviour for opening multiple windows, * and render them in whatever manner you want.</p> * - * <p>Standard behavior for an Activity is to be destroyed and - * recreated when the devices orientation is changed. This will cause + * <p>The standard behavior for an Activity is to be destroyed and + * recreated when the device orientation or any other configuration changes. This will cause * the WebView to reload the current page. If you don't want that, you - * can set your Activity to handle the orientation and keyboardHidden + * can set your Activity to handle the {@code orientation} and {@code keyboardHidden} * changes, and then just leave the WebView alone. It'll automatically - * re-orient itself as appropriate.</p> + * re-orient itself as appropriate. Read <a + * href="{@docRoot}guide/topics/resources/runtime-changes.html">Handling Runtime Changes</a> for + * more information about how to handle configuration changes during runtime.</p> + * + * + * <h3>Building web pages to support different screen densities</h3> + * + * <p>The screen density of a device is based on the screen resolution. A screen with low density + * has fewer available pixels per inch, where a screen with high density + * has more — sometimes significantly more — pixels per inch. The density of a + * screen is important because, other things being equal, a UI element (such as a button) whose + * height and width are defined in terms of screen pixels will appear larger on the lower density + * screen and smaller on the higher density screen. + * For simplicity, Android collapses all actual screen densities into three generalized densities: + * high, medium, and low.</p> + * <p>By default, WebView scales a web page so that it is drawn at a size that matches the default + * appearance on a medium density screen. So, it applies 1.5x scaling on a high density screen + * (because its pixels are smaller) and 0.75x scaling on a low density screen (because its pixels + * are bigger). + * Starting with API Level 5 (Android 2.0), WebView supports DOM, CSS, and meta tag features to help + * you (as a web developer) target screens with different screen densities.</p> + * <p>Here's a summary of the features you can use to handle different screen densities:</p> + * <ul> + * <li>The {@code window.devicePixelRatio} DOM property. The value of this property specifies the + * default scaling factor used for the current device. For example, if the value of {@code + * window.devicePixelRatio} is "1.0", then the device is considered a medium density (mdpi) device + * and default scaling is not applied to the web page; if the value is "1.5", then the device is + * considered a high density device (hdpi) and the page content is scaled 1.5x; if the + * value is "0.75", then the device is considered a low density device (ldpi) and the content is + * scaled 0.75x. However, if you specify the {@code "target-densitydpi"} meta property + * (discussed below), then you can stop this default scaling behavior.</li> + * <li>The {@code -webkit-device-pixel-ratio} CSS media query. Use this to specify the screen + * densities for which this style sheet is to be used. The corresponding value should be either + * "0.75", "1", or "1.5", to indicate that the styles are for devices with low density, medium + * density, or high density screens, respectively. For example: + * <pre> + * <link rel="stylesheet" media="screen and (-webkit-device-pixel-ratio:1.5)" href="hdpi.css" /></pre> + * <p>The {@code hdpi.css} stylesheet is only used for devices with a screen pixel ration of 1.5, + * which is the high density pixel ratio.</p> + * </li> + * <li>The {@code target-densitydpi} property for the {@code viewport} meta tag. You can use + * this to specify the target density for which the web page is designed, using the following + * values: + * <ul> + * <li>{@code device-dpi} - Use the device's native dpi as the target dpi. Default scaling never + * occurs.</li> + * <li>{@code high-dpi} - Use hdpi as the target dpi. Medium and low density screens scale down + * as appropriate.</li> + * <li>{@code medium-dpi} - Use mdpi as the target dpi. High density screens scale up and + * low density screens scale down. This is also the default behavior.</li> + * <li>{@code low-dpi} - Use ldpi as the target dpi. Medium and high density screens scale up + * as appropriate.</li> + * <li><em>{@code <value>}</em> - Specify a dpi value to use as the target dpi (accepted + * values are 70-400).</li> + * </ul> + * <p>Here's an example meta tag to specify the target density:</p> + * <pre><meta name="viewport" content="target-densitydpi=device-dpi" /></pre></li> + * </ul> + * <p>If you want to modify your web page for different densities, by using the {@code + * -webkit-device-pixel-ratio} CSS media query and/or the {@code + * window.devicePixelRatio} DOM property, then you should set the {@code target-densitydpi} meta + * property to {@code device-dpi}. This stops Android from performing scaling in your web page and + * allows you to make the necessary adjustments for each density via CSS and JavaScript.</p> + * + * */ @Widget public class WebView extends AbsoluteLayout |