WebView methods on same thread error

I have a android program (Java + html in a webview). I can call from the javascript to the Java code. But the other way around stopped working (after updating in eclipse).

So this is what I'm trying to do

• Make a webview (worked)
• calling in javascript to AndroidFunction.test(); (worked)
• the java test() function call webView.loadUrl("javascript:helloBack()"); (! not working anymore)

I tried to let it work with the WebView in the MainActivity, but it didnt work.

MainActivity.java

public void onCreate(Bundle savedInstanceState) {
    	super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final WebView webView = (WebView)findViewById(R.id.webView);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebChromeClient(new WebChromeClient());
        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);

        javascr = new Javascript(this, webView);
        webView.addJavascriptInterface(javascr, "AndroidFunction");
        webView.loadUrl("file:///android_asset/www/index.html");

        ....
}

Javascript.java

public class Javascript {	
	Context cont;
	WebView webView;
	
	Javascript(Context c, WebView w) {
		cont = c;
		webView = w;
	}

    // function called in the javascript by AndroidFunction.test();
	public void test() {
          // Breaking point!!!
		webView.loadUrl("javascript:helloBack()");
	}

Error:

03-24 11:47:50.103: W/WebView(21026): 	at com.android.org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:27)
03-24 11:47:50.103: W/WebView(21026): 	java.lang.Throwable: A WebView method was called on thread 'JavaBridge'. All WebView methods must be called on the same thread. (Expected Looper Looper{41ab68f8} called on Looper{41bb70a8}, FYI main Looper is Looper{41ab68f8})

03-24 11:47:50.103: W/WebView(21026): 	at android.webkit.WebView.checkThread(WebView.java:2063)
03-24 11:47:50.103: W/WebView(21026): 	at android.webkit.WebView.loadUrl(WebView.java:794)
03-24 11:47:50.103: W/WebView(21026): 	at com.example.hellobt.Javascript.test(Javascript.java:24)

03-24 11:47:50.103: W/WebView(21026): 	at com.android.org.chromium.base.SystemMessageHandler.nativeDoRunLoopOnce(Native Method)
03-24 11:47:50.103: W/WebView(21026): 	at com.android.org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:27)
03-24 11:47:50.103: W/WebView(21026): 	at android.os.Handler.dispatchMessage(Handler.java:102)

03-24 11:47:50.103: W/WebView(21026): 	at android.os.Looper.loop(Looper.java:137)
03-24 11:47:50.103: W/WebView(21026): 	at android.os.HandlerThread.run(HandlerThread.java:61)

Thanks for the answer. I edited the function in my Javascript file like this:

private void test(final String s) {
		webView.post(new Runnable() {
		    public void run() {
		    	webView.loadUrl("javascript:" + s + ";");
		    }
		});
		System.out.println("javscript done..");
	}

The JavaScript method is executed on a background (i.e. non-UI) thread. You need to call all Android View related methods on the UI thread. You can achieve what you need with:

mWebView.post(new Runnable() {
    @Override
    public void run() {
        mWebView.loadUrl(...).
    }
});

Which will post the task to run on the UI thread.

In my case nothing was shown in a WebView, so I prefer another way:

runOnUiThread(new Runnable() {
    @Override
    public void run() {
        final WebView webView = (WebView) findViewById(R.id.map);
        webView.loadDataWithBaseURL(...);
    }
});

Java version: You must to use Runnable interface and Post to Handler.

webView.post(new Runnable() {
          @Override
          public void run() {
             webView.loadUrl("file:///android_asset/www/index.html");
          }
       });

Kotlin version:

webView.post(new Runnable {
   webView.loadUrl("file:///android_asset/www/index.html")
})

This can be come over by using the post method. Please go through below code.

 m_targetView.post(new Runnable() {
                        @Override
                        public void run() {
                            m_targetView.loadUrl(".....");
                        }
                    });