android listview viewholder. when to use it, and when not to

Question

I have a ListView with a custom list adapter. In the getView() method, am using the ViewHolder 'pattern' as shown in the API Demos for ListView14.java. When i first render the list it seems to load correctly. However, the issue i'm running into is that when i scroll the list, i'm seeing the data for the list show up in the wrong rows (i.e. a TextView that should be in row 10 is showing up in row 2 for example). However, when I do not use the viewholder, and instead call findViewById() every time, then the list view renders correctly.

Answer 1

However, the issue i'm running into is that when i scroll the list, i'm seeing the data for the list show up in the wrong rows (i.e. a TextView that should be in row 10 is showing up in row 2 for example).

Most likely, you are improperly recycling your rows, such that the ViewHolders you are manipulating are not the right ones for the row you are returning.

Here is a free excerpt from one of my books that goes into more about row recycling -- perhaps it will help you identify where things are going wrong.

Answer 2

• I faced same problem
• Solved using below techninc
• Reason : Adapter not Loaded Frequentlyy.

• in Your Custom Adapter class add ViewHolder using Access Specifiers

  private static class ViewHolder {
  
          protected TextView itemName;
  
      }
  

In Get View method

    @Override

        public View getView(int position, View view, ViewGroup viewGroup) {

            // create a ViewHolder reference
            ViewHolder holder;

            //check to see if the reused view is null or not, if is not null then reuse it
            if (view == null) {
                holder = new ViewHolder();

                view = mLayoutInflater.inflate(R.layout.list_item, null);
                holder.itemName = (TextView) view.findViewById(R.id.list_item_text_view);

                // the setTag is used to store the data within this view
                view.setTag(holder);
            } else {
                // the getTag returns the viewHolder object set as a tag to the view
                holder = (ViewHolder)view.getTag();
            }
    // now Use Holder object toget Idss 

    holder.itemName.setText(" sample text based on position ");
    }

Important : And We should not set Any Tag for view object except Viewholder Object