/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.webkit; import android.annotation.Widget; import android.content.Context; import android.content.res.Configuration; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.Picture; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.net.http.SslCertificate; import android.os.Build; import android.os.Bundle; import android.os.CancellationSignal; import android.os.Looper; import android.os.Message; import android.os.ParcelFileDescriptor; import android.os.StrictMode; import android.print.PrintAttributes; import android.util.AttributeSet; import android.util.Log; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.View; import android.view.ViewDebug; import android.view.ViewGroup; import android.view.ViewTreeObserver; import android.view.accessibility.AccessibilityEvent; import android.view.accessibility.AccessibilityNodeInfo; import android.view.accessibility.AccessibilityNodeProvider; import android.view.inputmethod.EditorInfo; import android.view.inputmethod.InputConnection; import android.widget.AbsoluteLayout; import java.io.BufferedWriter; import java.io.File; import java.util.Map; /** *

A View that displays web pages. This class is the basis upon which you * can roll your own web browser or simply display some online content within your Activity. * It uses the WebKit rendering engine to display * web pages and includes methods to navigate forward and backward * through a history, zoom in and out, perform text searches and more.

*

To enable the built-in zoom, set * {@link #getSettings() WebSettings}.{@link WebSettings#setBuiltInZoomControls(boolean)} * (introduced in API level {@link android.os.Build.VERSION_CODES#CUPCAKE}). *

Note that, in order for your Activity to access the Internet and load web pages * in a WebView, you must add the {@code INTERNET} permissions to your * Android Manifest file:

* 
<uses-permission android:name="android.permission.INTERNET" />
* *

This must be a child of the {@code } * element.

* *

For more information, read * Building Web Apps in WebView.

* *

Basic usage

* *

By default, a WebView provides no browser-like widgets, does not * 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 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: * 

 * Uri uri = Uri.parse("http://www.example.com");
 * Intent intent = new Intent(Intent.ACTION_VIEW, uri);
 * startActivity(intent);
 *
*

See {@link android.content.Intent} for more information.

* *

To provide a WebView in your own Activity, include a {@code } in your layout, * or set the entire Activity window as a WebView during {@link * android.app.Activity#onCreate(Bundle) onCreate()}:

* 
 * WebView webview = new WebView(this);
 * setContentView(webview);
 *
* *

Then load the desired web page:

* 
 * // 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/");
 *
 * // 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", null);
 * // ... although note that there are restrictions on what this HTML can do.
 * // See the JavaDocs for {@link #loadData(String,String,String) loadData()} and {@link
 * #loadDataWithBaseURL(String,String,String,String,String) loadDataWithBaseURL()} for more info.
 *
* *

A WebView has several customization points where you can add your * own behavior. These are:

* * * *

Here's a more complicated example, showing error handling, * settings, and progress notification:

* * 
 * // Let's display the progress in the activity title bar, like the
 * // browser app does.
 * getWindow().requestFeature(Window.FEATURE_PROGRESS);
 *
 * webview.getSettings().setJavaScriptEnabled(true);
 *
 * final Activity activity = this;
 * webview.setWebChromeClient(new WebChromeClient() {
 *   public void onProgressChanged(WebView view, int progress) {
 *     // Activities and WebViews measure progress with different scales.
 *     // The progress meter will automatically disappear when we reach 100%
 *     activity.setProgress(progress * 1000);
 *   }
 * });
 * webview.setWebViewClient(new WebViewClient() {
 *   public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
 *     Toast.makeText(activity, "Oh no! " + description, Toast.LENGTH_SHORT).show();
 *   }
 * });
 *
 * webview.loadUrl("http://slashdot.org/");
 *
* *

Cookie and window management

* *

For obvious security reasons, your application has its own * cache, cookie store etc.—it does not share the Browser * application's data. *

* *

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 * {@link WebChromeClient} to provide your own behaviour for opening multiple windows, * and render them in whatever manner you want.

* *

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 {@code orientation} and {@code keyboardHidden} * changes, and then just leave the WebView alone. It'll automatically * re-orient itself as appropriate. Read Handling Runtime Changes for * more information about how to handle configuration changes during runtime.

* * *

Building web pages to support different screen densities

* *

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.

*

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 {@link android.os.Build.VERSION_CODES#ECLAIR}, WebView supports DOM, CSS, * and meta tag features to help you (as a web developer) target screens with different screen * densities.

*

Here's a summary of the features you can use to handle different screen densities:

*