Why is my ListView's `getView` Method Called Multiple Times and in an Apparently Random Order?

Custom List View Adapter's getView Method: In-Depth Analysis of Multiple Invocation

Question:

In a custom list adapter, why is the getView method called multiple times, seemingly in a haphazard order?

Answer:

The getView method in a custom list adapter can be called multiple times and in any order due to the inherent nature of how ListView works. Here's an explanation of the behaviors observed in the provided code:

ConvertViews:

The convertView parameter represents a view that is being recycled for reuse. When convertView is non-null, it indicates that the ListView has already measured and inflated a view for the corresponding position. Instead of creating a new view, the adapter reuses this recycled view.

getView Invocation Order:

There is no guaranteed order in which getView will be called for different positions. The ListView might call getView for multiple positions even before user input is received. This behavior is especially common when the ListView has a height set to wrap_content, as in the given XML layout.

Why getView is Called Multiple Times:

getView is called multiple times for each position due to the ListView's measurement process. When the ListView is first displayed, it measures several children out of the adapter to determine its own height. This measurement process triggers getView calls for the visible portion of the list.

Unpredictable ConvertViews:

As the user scrolls, the ListView may recycle views that are no longer visible and reuse them for new positions. This explains why the convertView parameter can be non-null even before the user has scrolled.

Conclusion:

While it may seem unusual, the behavior of getView being called multiple times and in an unpredictable order is not an issue. It is an inherent part of how ListView optimizes performance by reusing views and measuring only a subset of children for its initial layout.

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