Adding alert() support to a WebView - Android

MainActivity.java

/* 
  Retrieved from https://web.archive.org/web/20160516165158/http://lexandera.com/2009/01/adding-alert-support-to-a-webview/
*/

final WebView browser = (WebView)findViewById(R.id.browser);  
/* JavaScript must be enabled if you want it to work, obviously */   
browser.getSettings().setJavaScriptEnabled(true);  
  
final Context myApp = this;  
  
/* WebChromeClient must be set BEFORE calling loadUrl! */  
browser.setWebChromeClient(new WebChromeClient() {  
    @Override  
    public boolean onJsAlert(WebView view, String url, String message, final android.webkit.JsResult result)   
    {  
        new AlertDialog.Builder(myApp)  
            .setTitle("javaScript dialog")  
            .setMessage(message)  
            .setPositiveButton(android.R.string.ok,  
                    new AlertDialog.OnClickListener()   
                    {  
                        public void onClick(DialogInterface dialog, int which)   
                        {  
                            result.confirm();  
                        }  
                    })  
            .setCancelable(false)  
            .create()  
            .show();  
          
        return true;  
    };  
});  
  
/* load a web page which uses the alert() function */  
browser.loadUrl("http://lexandera.com/files/jsexamples/alert.html"); 

Erro: http://prntscr.com/nn0oee

package br.com.aaaaa;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.WebChromeClient;
import android.webkit.WebView;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;

public class MainActivity extends AppCompatActivity {

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


        final WebView browser = (WebView)findViewById(R.id.browser);
        /* JavaScript must be enabled if you want it to work, obviously */
        browser.getSettings().setJavaScriptEnabled(true);

        final Context myApp = this;

        /* WebChromeClient must be set BEFORE calling loadUrl! */
        browser.setWebChromeClient(new WebChromeClient() {
            @Override
            public boolean onJsAlert(WebView view, String url, String message, final android.webkit.JsResult result)
            {
                new AlertDialog.Builder(myApp)
                        .setTitle("javaScript dialog")
                        .setMessage(message)
                        .setPositiveButton(android.R.string.ok,
                                new AlertDialog.OnClickListener()
                                {
                                    public void onClick(DialogInterface dialog, int which)
                                    {
                                        result.confirm();
                                    }
                                })
                        .setCancelable(false)
                        .create()
                        .show();

                return true;
            };
        });

        /* load a web page which uses the alert() function */
        browser.loadUrl("http://lexandera.com/files/jsexamples/alert.html");


    }
}