Android - Webview click Error Calling method on Npobject

Question

I’m trying to perform an action in the Android app by clicking an html element in the webview. When clicking on the element, the event is activated but the following error occurs in the alert(err) javascript inside the Try catch:

Error: Error Calling method on Npobject.

Error in Android log:

 android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
     at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6433)
     at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:878)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.requestLayout(View.java:16683)
     at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.requestLayout(View.java:16683)
     at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
     at android.view.View.requestLayout(View.java:16683)
     at android.view.View.setFlags(View.java:9055)
     at android.view.View.setVisibility(View.java:6127)
     at com.example.base.googlcloudvideointelligence.MainActivity$WebAppInterface.showMenu(MainActivity.java:131)
     at com.android.org.chromium.base.SystemMessageHandler.nativeDoRunLoopOnce(Native Method)
     at com.android.org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:24)
     at android.os.Handler.dispatchMessage(Handler.java:102)
     at android.os.Looper.loop(Looper.java:136)
     at android.os.HandlerThread.run(HandlerThread.java:61)

I’m guessing it’s a scope problem. Just follow my code:

public class MainActivity extends AppCompatActivity {
    Button btnFinalizar;
    WebView webView;
    WebSettings webSettings;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        btnFinalizar = (Button) findViewById(R.id.btnFinalizar);
        webView = (WebView) findViewById(R.id.webView);

        webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setDomStorageEnabled(true);

        webView.addJavascriptInterface(new WebAppInterface(this), "Android");
        webSettings.setAllowUniversalAccessFromFileURLs(true);

        webView.setWebChromeClient(new WebChromeClient() {
            @Override
            public boolean onConsoleMessage(ConsoleMessage consoleMessage) {
                Log.d("MeuApp", consoleMessage.message() + " -- From line "
                    + consoleMessage.lineNumber() + " of "
                    + consoleMessage.sourceId());
                return super.onConsoleMessage(consoleMessage);
            }


        });
        webView.setWebViewClient(new WebViewClient ());
        webView.loadUrl("http://urlexemplo.com.br");
    }

    public class WebAppInterface {

        Context mContext;

        WebAppInterface(Context c) {
            mContext = c;
        }

        @JavascriptInterface
        public void showMenu() {
            Toast.makeText(mContext, "AQUI FUNCIONA", Toast.LENGTH_SHORT).show();
            btnFinalizar.setVisibility(View.VISIBLE);
        }
    }
}

The function showMenu() is run on Android. I put a Toast to test and it is called, LESS btnFinalizar.setVisibility(View.VISIBLE); And here’s my Javascript that’s working.

$("body").on('click', '.step-question .go-step', function(event) {
    event.preventDefault();
    /* Act on the event */

    try {
        window.Android.showMenu();
        alert('foi');
    } catch(err) { alert(err); }
});

What I need to do for the btnFinalizar.setVisibility(View.VISIBLE); work? PS: this command is functional outside that class WebAppInterface

Answer 1

I did it. webview creates a thread that loses access to the parent class MainActivity. So I had to override the parent thread and call it. I just modified the method code showMenu()

    @JavascriptInterface
    public void showMenu() {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                btnFinalizar.setVisibility(View.VISIBLE);
            }
        });
    }