How does the recycling mechanism in the list view work?

First of all, I didn't understand the recycling mechanism of the list view and the converter view usage mechanism, but after a few days of research, I was able to understand some of the mechanisms of the list view in the images listed in android.amberfog.

If the questioner creates a list view with an adapter that shows the maximum number of lines that can be displayed on the screen, you will see that scrolling through that list view does not increase the number of lines. This is because of the trick that Android is using to make the list view work more efficiently and faster. Here's the truth of the list view shown in the image above. The list view has seven visible items by default. If the user scrolls, the first item will no longer be visible, and the getView() function passes the view (the first item) to the recycler. Therefore

System.out.println("getview:"+position+" "+convertView);

Put the above code into the getView() function as shown below.

public View getView(final int position, View convertView, ViewGroup parent)
{
    System.out.println("getview:"+position+" "+convertView);
    View row=convertView;
    if(row==null)
    {
        LayoutInflater inflater=((Activity)context).getLayoutInflater();
        row=inflater.inflate(layoutResourceId, parent,false);

        holder=new PakistaniDrama();
        holder.tvDramaName=(TextView)row.findViewById(R.id.dramaName);
        holder.cbCheck=(CheckBox)row.findViewById(R.id.checkBox);

        row.setTag(holder);

    }
    else
    {
        holder=(PakistaniDrama)row.getTag();
    }
            holder.tvDramaName.setText(dramaList.get(position).getDramaName());
    holder.cbCheck.setChecked(checks.get(position));
            return row;
    }

In the column currently shown, you will see the converter view as a null value through the logcat. This is because the recycler initially does not contain any views, so the getView() function creates a new view for the items shown. However, the first item is sent to Recycler with the status of the item (for example, in the above code, the textView phrase or check box is checked). The list view now uses the view (converter view) in the recycler without creating a new view, and since the new eighth item was drawn using the converter view, the logcat will show that the converter view is not a null value. Therefore, if you have checked the check box of the first item, the check box of the eighth item will be seen as already checked. This is how the view of the list view is reused for performance optimization.

Important facts

1. Never set layout_height and layout_width of the list view, as the function forces some child views to measure the height of the view, resulting in unexpected results such as returning the converter view before scrolling the list. Always use match_parent or a fixed width/height value.

2.If you want to use a layout or view after a list view, and if you set layout_height of a list view to fill_parent, it would be better to put the list view in the layout. For example, if you fix the height and width of a linear layout to a specific value and set the height and width of the list view to be the same as the linear layout, the list view will have the same height and width as the layout. This will inform the getView() function to render the view with the correct height and width, and the getView() function will not return the converter view before it continues to read and scroll through any item to measure the height or width of the view. As a result of testing, the way the list view was included in the linear layout worked magically well without causing any problems.

01-01 14:49:36.606: I/System.out(13871): getview 0 null
01-01 14:49:36.636: I/System.out(13871): getview 0 android.widget.RelativeLayout@406082c0
01-01 14:49:36.636: I/System.out(13871): getview 1 android.widget.RelativeLayout@406082c0
01-01 14:49:36.646: I/System.out(13871): getview 2 android.widget.RelativeLayout@406082c0
01-01 14:49:36.646: I/System.out(13871): getview 3 android.widget.RelativeLayout@406082c0
01-01 14:49:36.656: I/System.out(13871): getview 4 android.widget.RelativeLayout@406082c0
01-01 14:49:36.666: I/System.out(13871): getview 5 android.widget.RelativeLayout@406082c0
01-01 14:49:36.666: I/System.out(13871): getview 0 android.widget.RelativeLayout@406082c0
01-01 14:49:36.696: I/System.out(13871): getview 0 android.widget.RelativeLayout@406082c0
01-01 14:49:36.706: I/System.out(13871): getview 1 null
01-01 14:49:36.736: I/System.out(13871): getview 2 null
01-01 14:49:36.756: I/System.out(13871): getview 3 null
01-01 14:49:36.776: I/System.out(13871): getview 4 null

My explanation may not have been perfect, but I spent a few days trying to understand it. So I think other beginners like me will be able to get help from my experience, and the way that list views work is so complicated and clever that it's hard for beginners to understand, so I hope this answer will give people a little more understanding of how strong list views work.