Let Java and JavaScript interact

This post is for reference from: Http://droidyue.com/blog/2014/09/20/interaction-between-java-and-javascript-in-android/

When we use WebView, we can let the Java code and the JavaScript code in the Web page interact, this article simply explains how the two interact.

One, JS call Java code

1.1 The Code of the Web page:

< HTML > <  type= "Text/javascript">    function toastmessage (message) {        Window.control.toastMessage (Message)    }    function Sumtojava (number1, number2) {       Window.control.onSumResult (Number1 + number2)    }</script>  Java-javascript Interaction in Android</html>

Can see, this page code has JS code, the main code snippet is as follows:

    function  toastmessage (message) {        window.control.toastMessage (message)    }      function  Sumtojava (Number1, number2) {       + number2)    }

One way to find out here: window.control.xxxxx. Here the control needs to be implemented on the Android side, the Web page only need to call on the line.

The invocation format is:window.jsInterfaceName.methodName (parametervalues) In this example we are using control as the injected interface name, so it becomes:

Window.control.toastMessage (Message)

1.2 Android Terminal

 PackageCom.example.javajsinteractiondemo;ImportAndroid.annotation.SuppressLint;Importandroid.app.Activity;ImportAndroid.os.Bundle;ImportAndroid.util.Log;ImportAndroid.view.Menu;ImportAndroid.webkit.JavascriptInterface;Importandroid.webkit.WebChromeClient;Importandroid.webkit.WebSettings;ImportAndroid.webkit.WebView;Importandroid.webkit.WebViewClient;ImportAndroid.widget.Toast; Public classMainactivityextendsActivity {Private Static FinalString LogTag = "Mainactivity"; @SuppressLint ("Javascriptinterface") @Overrideprotected voidonCreate (Bundle savedinstancestate) {Super. OnCreate (savedinstancestate); Setcontentview (R.layout.activity_main);
      FinalWebView Mywebview =(WebView) Findviewbyid (R.id.mywebview); WebSettings Settings=mywebview.getsettings (); Settings.setjavascriptenabled (true); Mywebview.addjavascriptinterface ( new Jsinteration (), "Control"); Mywebview.setwebchromeclient (Newwebchromeclient () {}); Mywebview.loadurl ("File:///android_asset/js_java_interaction.html"); }   Public class  jsinteration {@JavascriptInterface Public voidtoastmessage (String message) {Toast.maketext (Getapplicationcontext (), message, Toast.length_long). Show (); } @JavascriptInterface Public voidOnsumresult (intresult) {log.i (LogTag,"Onsumresult result=" +result); }  }}

you can see that the webview is used in the addjavascriptinterface method defines an injection interface and class: Control & Jsinteration. Then after the jsinteration to write the implementation of the method: Toastmessage & Onsumresult, so in the JS call when Android will know what is the method of JS.

Second, Java calls JS

The method of invoking JS is very simple and the loading page is exactly the same

Basic format: Webview.loadurl ("Javascript:methodname (parametervalues)")

Example 1:

No parameter method

String call = "Javascript:sayhello ()"; Webview.loadurl (call);

Example 2:

Note that you need to escape double quotes for a string as a parameter value

String call = "Javascript:alertmessage (\" "+" content "+" \ ")", Webview.loadurl (call);

For information on how to safely interact and avoid injection attacks, please refer to: http://mobile.51cto.com/aprogram-452011.htm

For information on how to get the return value of JS, please refer to: Http://droidyue.com/blog/2014/09/20/interaction-between-java-and-javascript-in-android/

Let Java and JavaScript interact