Android ViewPager + Webview, ClassCastException! Need webview in a viewpager

Question

I am trying to create a horizontal "listview" of webviews. As suggested by a previous answer to a question, I am using the ViewPager library from the compatibility pack.

Unfortunately when I go to add my webview to the view collection, using

((ViewPager) collection).addView((View)mainContent,0);

I get the casting issue.

09-07 20:45:30.690: ERROR/AndroidRuntime(8166): java.lang.ClassCastException: android.webkit.WebView cannot be cast to android.support.v4.view.ViewPager

This crashes the app.

Now it almost makes sense, casting different data types makes things go wrong, but in a ViewPager example app I had, they are casting TextView to the ViewPager which is a view...

I just don't know what other way to actually "store" my views and display them in the app! I have

private class AwesomePagerAdapter extends PagerAdapter{
    LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    @Override
    public int getCount() {
        return NUM_AWESOME_VIEWS;
    }


    @Override
    public Object instantiateItem(View collection, int position) {

        ViewPager viewPager = (ViewPager) collection;

        collection = layoutInflater.inflate(R.layout.maincontentview, null);

        WebView mainContent = (WebView)collection.findViewById(R.id.mainContent);

        JSInterface jsInterface = new JSInterface(mainContent);


        Display display = getWindowManager().getDefaultDisplay(); 
        int width = display.getWidth();
        int height = display.getHeight();
        //jsInterface.fit(width, height);
        //jsInterface.flip(width, height);

        WebSettings webSettings = mainContent.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setPluginsEnabled(true);
        webSettings.setLoadsImagesAutomatically(true);
        webSettings.setSupportZoom(false);

        mainContent.setVerticalScrollBarEnabled(false);
        mainContent.setHorizontalScrollBarEnabled(false);

        /*mainContent.setOnTouchListener(new View.OnTouchListener() {
            public boolean onTouch(View v, MotionEvent event) {
                return(event.getAction() == MotionEvent.ACTION_MOVE);
            }
        });*/

        mainContent.setWebViewClient(new WebViewClient()
        {
            @Override
            public void onPageFinished(WebView view, String url) 
            {
                 /*mainContent.loadUrl("javascript:var script = document.createElement('script');" +  
                            "script.type = 'text/javascript';" +
                            "script.src = 'jquery.min.js';" + 
                            "document.getElementsByTagName('head')[0].appendChild(script);");*/
                WebView mainContent = (WebView)view.findViewById(R.id.mainContent);
                 Display display = getWindowManager().getDefaultDisplay(); 
                 int width = display.getWidth();
                 int height = display.getHeight();
                 mainContent.loadUrl("javascript:fit("+width+","+height+");");
                 mainContent.loadUrl("javascript:flip("+width+","+height+");");

            }
        });

        mainContent.setWebChromeClient(new WebChromeClient()
        {
            @Override
            public boolean onJsAlert(WebView view, String url, String message, JsResult result) 
            {
                Log.e("alert triggered", message);
                return false;         
            }
        });

        //use load file from string, article[i].html
        mainContent.loadUrl("file:///android_asset/cache_manifest_test.html");

        ((ViewPager) collection).addView((View)mainContent,0);

        return mainContent;
    }

    /**
     * Remove a page for the given position.  The adapter is responsible
     * for removing the view from its container, although it only must ensure
     * this is done by the time it returns from {@link #finishUpdate()}.
     *
     * @param container The containing View from which the page will be removed.
     * @param position The page position to be removed.
     * @param object The same object that was returned by
     * {@link #instantiateItem(View, int)}.
     */
    @Override
    public void destroyItem(View collection, int position, Object view) {
        ((ViewPager) collection).removeView((WebView) view);
    }



    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view==((WebView)object);
    }


    /**
     * Called when the a change in the shown pages has been completed.  At this
     * point you must ensure that all of the pages have actually been added or
     * removed from the container as appropriate.
     * @param container The containing View which is displaying this adapter's
     * page views.
     */
    @Override
    public void finishUpdate(View arg0) {}


    @Override
    public void restoreState(Parcelable arg0, ClassLoader arg1) {}

    @Override
    public Parcelable saveState() {
        return null;
    }

    @Override
    public void startUpdate(View arg0) {}

}

Answer 1

this works... I've had to cut some of the webview stuff down as i was getting errors with that.

The main problem you had was using the 'collection' view rather than creating a new one.

package com.msi.awesomepager;

import android.app.Activity;
import android.content.Context;   
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.Display;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.JsResult;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.TextView;

public class AwesomePagerActivity extends Activity {

    private ViewPager awesomePager;
    private static int NUM_AWESOME_VIEWS = 20;
    private Context context;
    private AwesomePagerAdapter awesomeAdapter;
    LayoutInflater inflater ;



    /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    context = this;

    inflater = (LayoutInflater)
            context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    awesomeAdapter = new AwesomePagerAdapter();
    awesomePager = (ViewPager) findViewById(R.id.awesomepager);
    awesomePager.setAdapter(awesomeAdapter);

}

private class AwesomePagerAdapter extends PagerAdapter{

    @Override
    public int getCount() {
        return NUM_AWESOME_VIEWS;
    }


    @Override
    public Object instantiateItem(View collection, int position) {

        View layout; 
        LayoutInflater mInflater =  (LayoutInflater)
                context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        layout  = mInflater.inflate(R.layout.maincontentview, null);

        WebView mainContent = (WebView)layout.findViewById(R.id.mainContent);

        mainContent.getSettings().setJavaScriptEnabled(true);

        WebSettings webSettings = mainContent.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setBuiltInZoomControls(true);
        mainContent.requestFocusFromTouch();

        mainContent.setWebViewClient(new WebViewClient());
        mainContent.setWebChromeClient(new WebChromeClient());

        mainContent.loadUrl("file:///android_asset/test.html");

        ((ViewPager) collection).addView((View)layout,0);

        return layout;
    }

    /**
     * Remove a page for the given position.  The adapter is responsible
     * for removing the view from its container, although it only must ensure
     * this is done by the time it returns from {@link #finishUpdate()}.
     *
     * @param container The containing View from which the page will be removed.
     * @param position The page position to be removed.
     * @param object The same object that was returned by
     * {@link #instantiateItem(View, int)}.
     */
    @Override
    public void destroyItem(View collection, int position, Object view) {
        ((ViewPager) collection).removeView((View) view);
    }



    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view==((View)object);
    }


    /**
     * Called when the a change in the shown pages has been completed.  At this
     * point you must ensure that all of the pages have actually been added or
     * removed from the container as appropriate.
     * @param container The containing View which is displaying this adapter's
     * page views.
     */
    @Override
    public void finishUpdate(View arg0) {}


    @Override
    public void restoreState(Parcelable arg0, ClassLoader arg1) {}

    @Override
    public Parcelable saveState() {
        return null;
    }

    @Override
    public void startUpdate(View arg0) {}

   }

}

Hope this helps. M