一、html中通過js調用java代碼
javascript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（注意這裏只是一般的意思，並不是java中接口的含義），這個接口其實是一個一般的類，同時爲這個接口取一個別名。這個過程如下：
mWebView.addJavascriptInterface(new DemoJavaScriptInterface(), "demo");
new DemoJavaScriptInterface就是這個接口，demo就是這個接口的別名。
上面的代碼執行之後在html的js中就能通過別名（這裏是“demo”）來調用newDemoJavaScriptInterface類中的任何方法。
如我們想讓html中的一個button點擊之後調用java中的函數可以這樣：
<input type="button" value="click me" onclick="window.demo.clickOnAndroid()"/>
但是因爲安全問題，在Android4.4中(如果應用的android:targetSdkVersion數值爲19+)JS只能訪問帶有 @JavascriptInterface註解的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註解。
谷歌給出的代碼示例：
WebViewDemo.java
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;
}
}
}demo.html
<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>main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/intro"
android:padding="4dip"
android:textSize="16sp"
/>
<WebView
android:id="@+id/webview"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
/>
</LinearLayout>二、Android調用js
上面的代碼在演示如何在js中調用java代碼的同時也演示瞭如何在java中調用js
調用形式：
mWebView.loadUrl("javascript:wave()");
其中wave（）是js中的一個方法，當然你可以把這個方法改成其他的方法，也就是android調用其他的方法。