Android : Javascript function ใน webview คลิกแล้วไม่ทำงาน

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        String url=("xxx");
        WebView WebViw = (WebView) findViewById(R.id.webView);
        WebViw.loadUrl(url);
        WebViw.getSettings().setJavaScriptEnabled(true);
        WebViw.setWebViewClient(new MyWebViewClient());

    }
    //เปิดลิงค์ในWebview
    private class MyWebViewClient extends WebViewClient {

        @Override
        public  boolean shouldOverrideUrlLoading(WebView view, String url ){
            view.loadUrl(url);
            return true;
        }

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

}