What is the cause of this error in XML parser?

Question

I can usually deal with errors that appear on logcat, but this logcat error strikes me as very out worldly, the error causes my the application to crash, the onPreExecute method is initated and the list shows up as loading, however the list never shows up and crashes. I already have much of the code in an Asynctask. I appreciate your time, I'm quite new at Android programming:

11-30 11:48:56.126: E/AndroidRuntime(1045): FATAL EXCEPTION: main
11-30 11:48:56.126: E/AndroidRuntime(1045): Process: com.example.clinicbooker, PID: 1045
11-30 11:48:56.126: E/AndroidRuntime(1045): java.lang.NullPointerException
11-30 11:48:56.126: E/AndroidRuntime(1045):     at com.example.clinicbooker.LazyAdapter.getView(LazyAdapter.java:54)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.AbsListView.obtainView(AbsListView.java:2263)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1263)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.ListView.onMeasure(ListView.java:1175)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.View.measure(View.java:16458)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.View.measure(View.java:16458)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.View.measure(View.java:16458)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.View.measure(View.java:16458)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2289)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.View.measure(View.java:16458)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1914)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1111)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1293)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.Choreographer.doFrame(Choreographer.java:532)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.os.Handler.handleCallback(Handler.java:733)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.os.Handler.dispatchMessage(Handler.java:95)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.os.Looper.loop(Looper.java:137)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at java.lang.reflect.Method.invokeNative(Native Method)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at java.lang.reflect.Method.invoke(Method.java:515)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-30 11:48:56.126: E/AndroidRuntime(1045):     at dalvik.system.NativeStart.main(Native Method)

More spefically, this logcat points to an error in my Adapter class at line 54:That would be TextView id=(TextView)vi.findViewById(R.id.id);

Adapter class as seen below:

public class LazyAdapter extends BaseAdapter {

    Context context;
    HashMap<String, String> resultp = new HashMap<String, String>();
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater = null;
    public ImageLoader imageLoader;

    public LazyAdapter(Context contextActivity , ArrayList<HashMap<String, String>> d) {
       this.context=contextActivity;
        data=d;
        imageLoader=new ImageLoader(context);
    }

    public int getCount() {
        return data.size();
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    public View getView(final int position, View convertView, ViewGroup parent) {   
        View vi=convertView;

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

        View itemView=inflater.inflate(R.layout.book_list_row,parent,false);

        resultp=data.get(position);

        TextView id=(TextView)vi.findViewById(R.id.id); //NPE ERROR POINTS HERE
        TextView title = (TextView)vi.findViewById(R.id.menu_name); 
        TextView description = (TextView)vi.findViewById(R.id.address); 
        TextView bookingDate = (TextView)vi.findViewById(R.id.book_date); 
        TextView bookingTime = (TextView)vi.findViewById(R.id.book_time);
        ImageView thumb_image=(ImageView)vi.findViewById(R.id.list_image); 


        // Setting all values in listview
        id.setText(resultp.get(BookScreen.KEY_ID)); 
        title.setText(resultp.get(BookScreen.KEY_TITLE));
        description.setText(resultp.get(BookScreen.KEY_ADDRESS));
        bookingDate.setText(resultp.get(BookScreen.KEY_DATE));
        bookingTime.setText(resultp.get(BookScreen.KEY_TIME));
        imageLoader.DisplayImage(resultp.get(BookScreen.KEY_THUMB_URL), thumb_image);

        itemView.setOnClickListener(new OnClickListener(){

            public void onClick(View arg0) {
                resultp=data.get(position);
                Intent intent=new Intent(context,SingleItemView.class);
                intent.putExtra("id",resultp.get(BookScreen.KEY_ID));
                intent.putExtra("title",resultp.get(BookScreen.KEY_TITLE));
                intent.putExtra("address",resultp.get(BookScreen.KEY_ADDRESS));
                intent.putExtra("date",resultp.get(BookScreen.KEY_DATE));
                intent.putExtra("time",resultp.get(BookScreen.KEY_TIME));
                intent.putExtra("thumbnail",resultp.get(BookScreen.KEY_THUMB_URL));
                context.startActivity(intent);
            }
        });
        return vi;
    }
}

What do these errors mean : AbsListView, ListView, LinearLayout,FrameLayout . Is my xml file that I am trying to parse incompatible with what code I have?

My main activity:

public class BookScreen extends Activity {

    //array
    ArrayList<HashMap<String, String>> songsList;
    ProgressDialog mProgressDialog;
    // All static variables
    static final String URL = "https://dl.dropboxusercontent.com/u/42241589/test.xml";
    // XML node keys
    static final String KEY_CLINIC = "clinic"; // parent node
    static final String KEY_ID = "id";
    static final String KEY_TITLE = "title";
    static final String KEY_DATE = "date";
    static final String KEY_TIME = "time";
    static final String KEY_ADDRESS = "address";
    static final String KEY_THUMB_URL = "thumbnail";
    ListView list;
    LazyAdapter adapter;

    @SuppressLint("NewApi")
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.book_main);
        new DownloadXML().execute();
    }

    private class DownloadXML extends AsyncTask<Void, Void, Void> {

        protected void onPreExecute() {
            super.onPreExecute();
            mProgressDialog = new ProgressDialog(BookScreen.this);
            mProgressDialog.setTitle("List is loading");
            mProgressDialog.setMessage("Loading...");
            mProgressDialog.setIndeterminate(false);
            mProgressDialog.show();
        }

        protected Void doInBackground(Void... params) {
            songsList = new ArrayList<HashMap<String, String>>();
            XMLParser parser = new XMLParser();
            String xml = parser.getXmlFromUrl(URL); // getting XML from URL
            Document doc = parser.getDomElement(xml); // getting DOM element
            try {
                NodeList nl = doc.getElementsByTagName(KEY_CLINIC); //define parent node
                // looping through all song nodes &lt;song&gt;
                for (int i = 0; i < nl.getLength(); i++) {
                    // creating new HashMap
                    HashMap<String, String> map = new HashMap<String, String>();
                    Element e = (Element) nl.item(i);
                    // adding each child node to HashMap key =&gt; value
                    map.put(KEY_ID, parser.getValue(e, KEY_ID));
                    map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
                    map.put(KEY_DATE, parser.getValue(e, KEY_DATE));
                    map.put(KEY_TIME, parser.getValue(e, KEY_TIME));
                    map.put(KEY_ADDRESS, parser.getValue(e, KEY_ADDRESS));
                    map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
                    // adding HashList to ArrayList
                    songsList.add(map);
                }
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return null;
        }

        protected void onPostExecute(Void args) {
                list=(ListView)findViewById(R.id.list);

            // Getting adapter by passing xml data ArrayList
            adapter = new LazyAdapter(BookScreen.this, songsList);
            list.setAdapter(adapter);
            //Close dialog
            mProgressDialog.dismiss();
        }
    }
}

XML Folder book_main:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

    <ListView
        android:id="@+id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:divider="#b5b5b5"
        android:dividerHeight="1dp"
        android:listSelector="@drawable/list_selector" />

</LinearLayout>

book_list_row.xml :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:padding="5dip" >

    <!-- ListRow Left sied Thumbnail image -->

    <LinearLayout
        android:id="@+id/thumbnail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_marginRight="5dip"
        android:padding="3dip" >

        <ImageView
            android:id="@+id/list_image"
            android:layout_width="50dip"
            android:layout_height="50dip" 
            />
    </LinearLayout>

    <!-- Menu name -->

    <TextView
        android:id="@+id/menu_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/thumbnail"
        android:layout_toRightOf="@+id/thumbnail"
        android:text="@string/book_name"
        android:textColor="#040404"
        android:textSize="15sp"
        android:textStyle="bold"
        android:typeface="sans" />

    <!-- Description -->

    <TextView
        android:id="@+id/address"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/thumbnail"
        android:layout_below="@id/menu_name"
        android:layout_marginTop="1dip"
        android:layout_toRightOf="@+id/thumbnail"
        android:text="@string/book_address"
        android:textColor="#343434"
        android:textSize="10sp"
        tools:ignore="SmallSp" />

    <!-- Price -->

    <TextView
        android:id="@+id/book_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignTop="@id/menu_name"
        android:layout_marginRight="5dip"
        android:gravity="right"
        android:text="@string/book_date"
        android:textColor="#10bcc9"
        android:textSize="10sp"
        android:textStyle="bold"
        tools:ignore="SmallSp" />

    <TextView
        android:id="@+id/book_time"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/book_date"
        android:layout_centerVertical="true"
        android:gravity="right"
        android:text="@string/book_time"
        android:textColor="#10bcc9"
        android:textSize="10sp"
        android:textStyle="bold"
        tools:ignore="SmallSp" />

    <TextView 
        android:id="@+id/id"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
       > </TextView>

</RelativeLayout>

My ImageLoader

public class ImageLoader {

    MemoryCache memoryCache=new MemoryCache();
    FileCache fileCache;
    private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
    ExecutorService executorService;

    public ImageLoader(Context context){
        fileCache=new FileCache(context);
        executorService=Executors.newFixedThreadPool(5);
    }

    final int stub_id = R.drawable.no_image;
    public void DisplayImage(String url, ImageView imageView)
    {
        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);
        if(bitmap!=null)
            imageView.setImageBitmap(bitmap);
        else
        {
            queuePhoto(url, imageView);
            imageView.setImageResource(stub_id);
        }
    }

    private void queuePhoto(String url, ImageView imageView)
    {
        PhotoToLoad p=new PhotoToLoad(url, imageView);
        executorService.submit(new PhotosLoader(p));
    }

    private Bitmap getBitmap(String url)
    {
        File f=fileCache.getFile(url);

        //from SD cache
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;

        //from web
        try {
            Bitmap bitmap=null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(true);
            InputStream is=conn.getInputStream();
            OutputStream os = new FileOutputStream(f);
            Utils.CopyStream(is, os);
            os.close();
            bitmap = decodeFile(f);
            return bitmap;
        } catch (Exception ex){
           ex.printStackTrace();
           return null;
        }
    }

    //decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f){
        try {
            //decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f),null,o);

            //Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE=70;
            int width_tmp=o.outWidth, height_tmp=o.outHeight;
            int scale=1;
            while(true){
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                    break;
                width_tmp/=2;
                height_tmp/=2;
                scale*=2;
            }

            //decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize=scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {}
        return null;
    }

    //Task for the queue
    private class PhotoToLoad
    {
        public String url;
        public ImageView imageView;
        public PhotoToLoad(String u, ImageView i){
            url=u;
            imageView=i;
        }
    }

    class PhotosLoader implements Runnable {
        PhotoToLoad photoToLoad;
        PhotosLoader(PhotoToLoad photoToLoad){
            this.photoToLoad=photoToLoad;
        }

        @Override
        public void run() {
            if(imageViewReused(photoToLoad))
                return;
            Bitmap bmp=getBitmap(photoToLoad.url);
            memoryCache.put(photoToLoad.url, bmp);
            if(imageViewReused(photoToLoad))
                return;
            BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
            Activity a=(Activity)photoToLoad.imageView.getContext();
            a.runOnUiThread(bd);
        }
    }

    boolean imageViewReused(PhotoToLoad photoToLoad){
        String tag=imageViews.get(photoToLoad.imageView);
        if(tag==null || !tag.equals(photoToLoad.url))
            return true;
        return false;
    }

    //Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable
    {
        Bitmap bitmap;
        PhotoToLoad photoToLoad;
        public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
        public void run()
        {
            if(imageViewReused(photoToLoad))
                return;
            if(bitmap!=null)
                photoToLoad.imageView.setImageBitmap(bitmap);
            else
                photoToLoad.imageView.setImageResource(stub_id);
        }
    }

    public void clearCache() {
        memoryCache.clear();
        fileCache.clear();
    }

}

Answer 1

Change getView to

convertView = inflater.inflate(R.layout.book_list_row,parent,false);

and use

TextView id=(TextView) convertView.findViewById(R.id.id);
//similarly for other views

and return convertView in getView

Also use a ViewHolder

static class ViewHolder
{

       TextView id,title,description,bookingDate,bookingTime;   
       ImageView thumb_image;

}

Then change getView

public View getView(int position, View convertView, ViewGroup parent) { 
             ViewHolder holder; 

   if (convertView == null) {
    convertView = mInflater.inflate(R.layout.book_list_row, parent, false);
    holder = new ViewHolder(); 
    holder.id=(TextView)convertView.findViewById(R.id.id); 
    holder.title = (TextView)convertView.findViewById(R.id.menu_name); 
    holder.description = (TextView)convertView.findViewById(R.id.address); 
    holder.bookingDate = (TextView)convertView.findViewById(R.id.book_date); 
    holder.bookingTime = (TextView)convertView.findViewById(R.id.book_time);
    holder.thumb_image=(ImageView)convertView.findViewById(R.id.list_image);    
    convertView.setTag(holder); 
    } else { 
   holder = (ViewHolder) convertView.getTag(); 
   }
   holder.id.setText(resultp.get(BookScreen.KEY_ID)); 
   holder.title.setText(resultp.get(BookScreen.KEY_TITLE));
   holder.description.setText(resultp.get(BookScreen.KEY_ADDRESS));
   holder.bookingDate.setText(resultp.get(BookScreen.KEY_DATE));
   holder. bookingTime.setText(resultp.get(BookScreen.KEY_TIME));
   hodler.imageLoader.DisplayImage(resultp.get(BookScreen.KEY_THUMB_URL), thumb_image);

   convertView.setOnClickListener(new OnClickListener(){

        public void onClick(View arg0) {
            resultp=data.get(position);
            Intent intent=new Intent(context,SingleItemView.class);
            intent.putExtra("id",resultp.get(BookScreen.KEY_ID));
            intent.putExtra("title",resultp.get(BookScreen.KEY_TITLE));
            intent.putExtra("address",resultp.get(BookScreen.KEY_ADDRESS));
            intent.putExtra("date",resultp.get(BookScreen.KEY_DATE));
            intent.putExtra("time",resultp.get(BookScreen.KEY_TIME));
            intent.putExtra("thumbnail",resultp.get(BookScreen.KEY_THUMB_URL));
            context.startActivity(intent);
       }       
     });
   return convertView; 
}

Answer 2

I believe that getView() provide a parameter of type View. You should use that only in the whole getView. you are using three View objects inside getView() only. It becomes so confusing

Please use convertView only.