Android call Javascript from Java not working

Question

I've read many posts but I can't get my Android app call a Javascript function. This is what I have

public class BorrameActivity extends AppCompatActivity {

    private static BorrameActivity.MyJavaScriptInterface myJavaScriptInterface;
    private static WebView webView;

    public class MyJavaScriptInterface {
        Context mContext;

        MyJavaScriptInterface(Context c) {
            mContext = c;
        }

        @android.webkit.JavascriptInterface
        public void doEchoTest(String echo){
            Log.e("printer", echo);
            Toast toast = Toast.makeText(mContext, echo, Toast.LENGTH_SHORT);
            toast.show();
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_borrame);

        myJavaScriptInterface = new BorrameActivity.MyJavaScriptInterface(this);
        webView = (WebView) findViewById(R.id.mybrowserAuthorise);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.addJavascriptInterface(myJavaScriptInterface, "JSInterface");
        webView.loadUrl("file:///android_asset/loginProtocol.html");
        //webView.loadUrl("javascript:JSInterface.doEchoTest('test')"); // THIS WORKS!!
        webView.loadUrl("javascript:testEcho()"); // THIS DOES NOT WORK
    }
}

This works when I execute

webView.loadUrl("javascript:JSInterface.doEchoTest('test')");

But it doesn't work when the Javascript function is in loginProtocol.html:

webView.loadUrl("javascript:testEcho()");

Where

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width; user-scalable=0;" />
    <title></title>
</head>
<body style="visibility:visible">
    <!--    Used for debugging -->
    <h1>HELLO</h1>

    <script>
        function testEcho(){
               JSInterface.doEchoTest('This does not get printed in Android Log');
        }
    </script>
</body>
</html>

and

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.sedicii.app.sedicii.BorrameActivity">

    <WebView
        android:id="@+id/mybrowserAuthorise"
        android:layout_width="353dp"
        android:layout_height="442dp"/>

</LinearLayout>

The WebView seems to be loading correctly (I can see the HELLO from loginProtocol.html on the Android screen).

What am I missing?

SOLUTION I have to wait until the HTML page is loaded. Thanks @KosWarm

webView.setWebViewClient(new WebViewClient() {
    public void onPageFinished(WebView view, String url) {
        webView.loadUrl("javascript:testEcho()");
    }
});

Btw., I have also tried with window.JSInterface.doEchoTest('This does not get printed in Android Log'); and it doesn't work either — Mike
– Mike, Commented Mar 7, 2017 at 17:46

Amin Memariani · Accepted Answer · 2017-03-07 18:06:10Z

2

I think you just need to give parameter to your loadUrl method:

webView.loadUrl("javascript:testEcho('Hello World!')");

and your javascript function must look like:

function testEcho(testHello){
 window.JSInterface.doEchoTest(testHello);
}

edited Mar 7, 2017 at 18:06

answered Mar 7, 2017 at 17:52

Amin Memariani

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Comments

Community · Accepted Answer · 2017-05-23 12:00:21Z

1

You execute the method loadUrl twice At the second execution, the first page is closed, so its script can not be executed

The following page code works

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width; user-scalable=0;" />
    <title></title>
</head>
<body style="visibility:visible">
<!--    Used for debugging -->
<h1>HELLO</h1>

<script>
        function testEcho(){
               JSInterface.doEchoTest('This does not get printed in Android Log');
        }
        testEcho() //added this line
    </script>
</body>
</html>

Update

from this place Calling Javascript method from within webview in Android

rewrite Activity onCrete method as

        myJavaScriptInterface = new MyJavaScriptInterface(this);
        webView = (WebView) findViewById(R.id.mybrowserAuthorise);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.addJavascriptInterface(myJavaScriptInterface, "JSInterface");
        webView.loadUrl("file:///android_asset/loginProtocol.html");
        webView.setWebViewClient(new WebViewClient() {
        public void onPageFinished(WebView view, String url) {
            webView.loadUrl("javascript:testEcho()");
        }
        });

edited May 23, 2017 at 12:00

CommunityBot

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answered Mar 7, 2017 at 17:58

KosWarm

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4 Comments

Mike Over a year ago

Yes, testEcho() is executed now. But with this approach it always gets executed when the HTML page is loaded, also when I remove it's call from the Android Java code webView.loadUrl("javascript:testEcho()");. I would like to actually call the JS function from Android, not to load an html that automatically executes the function. Is calling loadUrl twice bad?

KosWarm Over a year ago

Maybe this is what you were looking for stackoverflow.com/questions/35906557/…

KosWarm Over a year ago

The loadUrl method is called asynchronously, so the second call was executed before the page was loaded. Because of what the script was not executed

Mike Over a year ago

OMG @KosWarm, you are right! I need to wait for the html page to be loaded in order to cal the JS function!!! I read so many posts, but not that one, THANKS!!!

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