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.
一個能顯示網頁內容的View。該類是你實現一個自己的瀏覽器，或者只是在activity中顯示網頁內容的基礎；它基于WebKit內核來顯示網頁，并且包含了實現前后翻頁、放大縮小，文字搜索方法。
從上面你應該了解到了基本功能，也就是顯示網頁。這篇文章中我們主要討論webview和Javascript的交互。如果你的js基礎比java基礎好的話那么采用這種方式做一些復雜的處理是個不錯的選擇。
js中調用java代碼其實就記住一點，webview設置一個和js交互的接口（注意這里只是一般的意思，并不是java中接口的含義），這個接口其實是一個一般的類，同時為這個接口取一個別名。這個過程如下：
但是因為安全問題，在Android4.2中(如果應用的android:targetSdkVersion數值為17+)JS只能訪問帶有 @JavascriptInterface注解的Java函數。因此如果你的開發版本比較高，需要在被調用的函數前加上@JavascriptInterface注解。
package com.google.android.webviewdemo;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.webkit.JsResult;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
/**
* Demonstrates how to embed a WebView in your activity. Also demonstrates how
* to have javascript in the WebView call into the activity, and how the activity
* can invoke javascript.
* <p>
* In this example, clicking on the android in the WebView will result in a call into
* the activities code in {@link DemoJavaScriptInterface#clickOnAndroid()}. This code
* will turn around and invoke javascript using the {@link WebView#loadUrl(String)}
* method.
* <p>
* Obviously all of this could have been accomplished without calling into the activity
* and then back into javascript, but this code is intended to show how to set up the
* code paths for this sort of communication.
*
*/
public class WebViewDemo extends Activity {
private static final String LOG_TAG = "WebViewDemo";
private WebView mWebView;
private Handler mHandler = new Handler();
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
mWebView = (WebView) findViewById(R.id.webview);
WebSettings webSettings = mWebView.getSettings();
webSettings.setSavePassword(false);
webSettings.setSaveFormData(false);
webSettings.setJavaScriptEnabled(true);
webSettings.setSupportZoom(false);
mWebView.setWebChromeClient(new MyWebChromeClient());
mWebView.addJavascriptInterface(new DemoJavaScriptInterface(), "demo");
mWebView.loadUrl("file:///android_asset/demo.html");
}
final class DemoJavaScriptInterface {
DemoJavaScriptInterface() {
}
/**
* This is not called on the UI thread. Post a runnable to invoke
* loadUrl on the UI thread.
*/
public void clickOnAndroid() {
mHandler.post(new Runnable() {
public void run() {
mWebView.loadUrl("javascript:wave()");
}
});
}
}
/**
* Provides a hook for calling "alert" from javascript. Useful for
* debugging your javascript.
*/
final class MyWebChromeClient extends WebChromeClient {
@Override
public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
Log.d(LOG_TAG, message);
result.confirm();
return true;
}
}
}
<html>
<script language="javascript">
/* This function is invoked by the activity */
function wave() {
alert("1");
document.getElementById("droid").src="android_waving.png";
alert("2");
}
</script>
<body>
<!-- Calls into the javascript interface for the activity -->
<a onClick="window.demo.clickOnAndroid()"><div style="width:80px;
margin:0px auto;
padding:10px;
text-align:center;
border:2px solid #202020;" >
<img id="droid" src="android_normal.png"/><br>
Click me!
</div></a>
</body>
</html>
個人總結：利用webView的這種方式在有些時候UI布局就可以轉成相應的html代碼編寫了，而html布局樣式之類有DW這樣強大的工具，而且網上很多源碼，很多代碼片。在UI和視覺效果上就會節省很多時間，重復發明輪子沒有任何意義。
