How to increment a value on view holder variables in android?

问题

I have a viewholder in my Android app and I tried to set an incremented value on a textfield. I tried it like following,

Activity

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null) {
        holder = new Holder();
        LayoutInflater inflater = (LayoutInflater) this.context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.menu_list_item, null);

        holder.textViewItemName = (TextView) convertView.findViewById(R.id.textViewItemName);
        holder.textViewPrice = (TextView) convertView.findViewById(R.id.textViewPrice);
        holder.imageView = (ImageView) convertView.findViewById(R.id.imageViewItem);
        holder.buttonPlus = (ButtonRectangle) convertView.findViewById(R.id.buttonPlus);
        holder.cartQtyTextView = (TextView) convertView.findViewById(R.id.textViewCartQty);
        holder.buttonMinus = (ButtonRectangle) convertView.findViewById(R.id.buttonMinus);
        convertView.setTag(holder);
    } else {
        holder = (Holder) convertView.getTag();
    }
    final MenuItem listItem = objects.get(position);
    holder.textViewItemName.setText(listItem.getItemName());
    holder.textViewPrice.setText("$ ".concat(String.valueOf(listItem.getItemPrice())));

    // Check & Set
    if (holder.buttonPlus != null) {
        holder.buttonPlus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (holder.cartQtyTextView != null) {
                    if (holder.inc >= 0) {
                        holder.cartQtyTextView.setText(String.valueOf(holder.inc++));
                    }
                }
            }
        });
    }
    holder.buttonPlus.setBackgroundColor(Color.WHITE);
    holder.buttonPlus.setTextColor(Color.parseColor("#333333"));

    // Check & Set
    if (holder.buttonMinus != null) {
        holder.buttonMinus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (holder.inc >= 0) {
                    holder.cartQtyTextView.setText(String.valueOf(holder.inc--));
                }
            }
        });
    }
    holder.buttonMinus.setBackgroundColor(Color.WHITE);
    holder.buttonMinus.setTextColor(Color.parseColor("#333333"));

    return convertView;

}

Holder

class Holder {
    ButtonRectangle buttonPlus;
    ButtonRectangle buttonMinus;
    TextView cartQtyTextView;
    TextView textViewItemName;
    TextView textViewPrice;
    ImageView imageView;
    int inc;
}

But this is incrementing randomly. How may I fix this?

回答1:

 > But this is incrementing randomly

that is because the viewholder may belong to different order-lines.

Example

in the beginning viewholder#1 belongs to orderline #1 with inc=2
if you scroll down the listbox orderline #1 becomes invisible and orderline #27 becomes visible. .
now orderline #27 is reusing viewholder#1 and with inc=2

how to fix this:

you need an objectmodell that store the data inc, articleid, quantity, unitprice, articlename, ......

 final OrderItem orderItem = (OrderItem) objects.get(position);
 ...
 orderItem.inc++;

See also https://stackoverflow.com/search?q=listview+random

回答2:

When you click button it gets the TextView corresponding to that position..

At OnClick button, get TextView of position you Clicked..
getText() of that TextView, implement condition to increase/decrease your inc then setText() to that TextView

I would also suggest to take a local variable inside your Adapter class instead of Holder class as it would be easy to manipulate its value..

回答3:

You also need to set a tag for the Button, if you want to manipulate the holder item.

   if (convertView == null) {
        ...
        holder.buttonPlus = (ButtonRectangle) convertView.findViewById(R.id.buttonPlus);
        holder.buttonPlus.setTag(holder);
        holder.buttonPlus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Holder current= (Holder) v.getTag();
                current.inc=current.inc+1;
                notifyDataSetChanged();
            }
        });
        convertView.setTag(holder);
    } else {
        holder = (Holder) convertView.getTag();
    }

来源：https://stackoverflow.com/questions/32497092/how-to-increment-a-value-on-view-holder-variables-in-android

标签

android

android-viewholder