Navigating from one page to another in a single webview Android

Question

I'm trying to go from one page to another in an already loaded webview when the user clicks on an image. The html pages are stored in a sub-folder in the asset folder.

Here's the java code

package com.vm;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.webkit.WebView;
import android.widget.ImageView;
import android.widget.TextView;

public class VmReadPreface extends VampireMusicActivity{

private WebView wv = null;    
private int pageIndex;
private String pagePath;    
private String[] pageList = {"file:///android_asset/preface/page_8.html",
        "file:///android_asset/preface/page_9.html","file:///android_asset/preface/page_10.html",
        "file:///android_asset/preface/page_11.html"};  
private int SelectedRow;
public static final String DEBUG_TAG = "VmMusic";   

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.preface);
        WebView wv;
        wv = (WebView) findViewById(R.id.web_holder);

         System.out.println(pageList[0]);
         System.out.println(pageList.length);
         pagePath=pageList[pageIndex];
         Log.i(DEBUG_TAG,"Page Path " + pagePath);

         wv.loadUrl(pagePath);


        final ImageView getNext_Page =(ImageView) findViewById(R.id.arrow_right);
        getNext_Page.setOnClickListener(NextClick);

        final ImageView getPrevious_Page =(ImageView) findViewById(R.id.arrow_left);
        getPrevious_Page.setOnClickListener(PreviousClick);
    }


    View.OnClickListener PreviousClick = new View.OnClickListener(){
        public void onClick(View v){
            GoPrevious();
        }
    };
    View.OnClickListener NextClick = new View.OnClickListener(){
        public void onClick(View v){
            GoNext();
        }
        };

    private void loadWebView(String s){
         Log.i(DEBUG_TAG,"String Is " + s);
         String finalFile = s;
         Log.i(DEBUG_TAG,"Final File Is " + finalFile);
         wv.loadUrl(finalFile);
       }

    private void GoNext(){
        int TotalRows = pageList.length;
        if((SelectedRow + 1)<TotalRows)
            {
            SelectedRow=SelectedRow +1;
            String s=pageList[SelectedRow];
            loadWebView(s);
            }
    }   

    private void GoPrevious(){
        if(SelectedRow>0)
        {
            SelectedRow = SelectedRow-1;
            String s=pageList[SelectedRow];
            loadWebView(s);
        }   
        }

    }

When the activity is launched the first page displays properly, however when I press the 'right arrow' to go to the next page, the log shows it finds the correct page (i.e. finalFile is now 'page_9') but the webview doesn't load.

dalvikm reports 'threadid=1: thread exiting with uncaught exception and then the runtime gives a fatal exception and a Null PointerException

What am I missing? Thanks

Answer 1

Delete WebView wv; from your onCreate-statement, as this makes it a local variable in onCreate