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View holder pattern

Why view holder pattern is important?

  • As you fling through your ListView, there's only a handful of views being shown at any given time. This means that you don't have to
  • instantiate a view for every item in your adapter; when a view scrolls off-screen, it can be reused, or recycled.
  • View recycling and the ViewHolder pattern are not the same. The ViewHolder pattern is solely to reduce the number of view.findViewById(int) calls you make. The ViewHolder pattern only works when you take advantage of view recycling.
  • In getView(int position, View convertView, ViewGroup parent), the convertView parameter is either null or it's a view that has been recycled: it will still have the data from a different list item bound to it.
  • Without the ViewHolder pattern, you can still take advantage of view recycling (i.e. not blindly instantiating views):

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