java - android studio中的类适配器

Question

我有包含 ImageView 和 TextView 的类适配器，我从执行后接收到数组列表，然后将这个数组传递给我的适配器，当运行我的应用程序时，它给我这个错误。

 java.lang.NullPointerException: Attempt to read from field 'android.widget.ImageView com.gmplatform.gmp.MainActivity_navagation_custmoer$itemAdapter3$ViewHolder.ivpic1' on a null object reference
                                                                  at com.gmplatform.gmp.MainActivity_navagation_custmoer$itemAdapter3$ViewHolder.access$2600(MainActivity_navagation_custmoer.java:2410)
                                                                  at com.gmplatform.gmp.MainActivity_navagation_custmoer$itemAdapter3.getView(MainActivity_navagation_custmoer.java:2372)

下面是适配器类

public class itemAdapter3 extends  BaseAdapter{

    private ArrayList<favouriteitems> itemCatalog;
    private int resource;
    private LayoutInflater inflater;

    public itemAdapter3(Context context, int resource, List<favouriteitems> objects) {
        //  super(context, resource, objects);
        itemCatalog = (ArrayList<favouriteitems>) objects;
        this.resource = resource;
        inflater = (LayoutInflater) getApplicationContext().getSystemService(LAYOUT_INFLATER_SERVICE);
    }



    public void notifyDataSetChanged() {
        super.notifyDataSetChanged();
    }
    @Override
    public int getCount() {
        return itemCatalog.size();
    }

    @Override
    public Object getItem(int position) {
        return itemCatalog.get(position);
    }

    @Override
    public long getItemId(int position) {
        return itemCatalog.indexOf(getItem(position));
    }


    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        final int pos = position;
        final favouriteitems items = itemCatalog.get(pos);
        ViewHolder  holder = null;
        if (convertView == null) {
            holder = new ViewHolder();
            convertView = inflater.inflate(resource, null);
            holder.ivpic1 = (ImageView) convertView.findViewById(R.id.iv);
            holder.st = (ImageView)convertView.findViewById(R.id.st);
            holder.sh=(ImageView)convertView.findViewById(R.id.sh);
            holder.name = (TextView) convertView.findViewById(R.id.t4);
            holder.pr = (TextView) convertView.findViewById(R.id.textView32);
            holder.av = (TextView) convertView.findViewById(R.id.av);
            holder.t5 = (TextView) convertView.findViewById(R.id.t5);
            final ViewHolder finalHolder = holder;



        }
        else {
            holder = (MainActivity_navagation_custmoer.itemAdapter3.ViewHolder) convertView.getTag();
        }

        final ProgressBar progressBar = (ProgressBar) convertView.findViewById(R.id.progressBar);

        // Then later, when you want to display image
        ImageLoader.getInstance().displayImage(itemCatalog.get(position).getM1().getLoc2().getItmc().getIt().getPic(), holder.ivpic1 , new ImageLoadingListener() {
            @Override
            public void onLoadingStarted(String imageUri, View view) {
                progressBar.setVisibility(View.VISIBLE);
            }

            @Override
            public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
                progressBar.setVisibility(View.GONE);
            }

            @Override
            public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
                progressBar.setVisibility(View.GONE);
            }

            @Override
            public void onLoadingCancelled(String imageUri, View view) {
                progressBar.setVisibility(View.GONE);
            }

        });


        holder.pr.setText(String.valueOf(itemCatalog.get(position).getM1().getLoc2().getItmc().getPrice() + " SR"));
        holder.name.setText(itemCatalog.get(position).getM1().getLoc2().getItmc().getIt().getName());

        if (itemCatalog.get(position).getM1().getLoc2().getItmc().isInSc() == true) {
            holder.sh.setImageResource(R.drawable.customern2);
        } else {
            holder.sh.setImageResource(R.drawable.customern1);
        }
        holder.t5.setText(itemCatalog.get(position).getM1().getmName()+" ("+itemCatalog.get(position).getM1().getLoc2().getArea()+" )");

        return convertView;
    }

    class ViewHolder {
        private ImageView ivpic1,sh,st;
        private TextView name,pr,t5,av;

    }
}

Answer 1

Constructor 有问题:

取消 super 调用的注释并运行它，您将不再出现空指针异常。

public itemAdapter3(Context context, int resource, List<favouriteitems> objects) {
          super(context, resource, objects);
        itemCatalog = (ArrayList<favouriteitems>) objects;
        this.resource = resource;
        inflater = (LayoutInflater) getApplicationContext().getSystemService(LAYOUT_INFLATER_SERVICE);
}