Why Does My ListView Adapter's `getView` Method Get Called Multiple Times and in What Order?

Custom ListView Adapter's getView Method: Multiple Invocations and Order Confusion

Custom list adapters often have their getView method called multiple times, and understanding the reasons and implications is crucial for proper ListView implementation.

getView Invocation Frequency

The getView method of a custom list adapter is responsible for creating and populating visible rows in a ListView. However, it's not uncommon for it to be called multiple times for the same position. This occurs because:

• Recycling: As the ListView scrolls, it recycles existing views to reduce the need for recreating them. This means that getView might be called again for a position to update the reused view.

getView Invocation Order

The order in which getView is called for different positions is not coherent. This is because the ListView may need to display rows in a different order due to its scrolling mechanism, which relies on optimizing the display for efficient rendering.

ConvertView Mystery

The convertView parameter in getView is passed to allow the adapter to reuse existing views. However, you may encounter cases where convertView is not null even though the ListView has not been scrolled. This is because, as previously mentioned, some child views are measured during layout to determine the ListView's initial size. These measured child views are treated as potential convert views for future scrolling.

Layout Considerations

Setting the ListView's height to wrap_content can lead to additional getView calls. This is because the ListView needs to measure some child views at layout time to determine its own size. These initial measurements can create convert views that are passed to getView before any scrolling occurs.

Best Practices

To improve the performance of your custom list adapter, consider the following best practices:

• Avoid heavy operations in getView to prevent slow rendering.
• Use ViewHolder objects to improve view reuse efficiency.
• Consider using a fixed height for the ListView or using a MeasureSpec.AT_MOST spec in the layout to prevent excessive getView calls during layout time.

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