Why Does My Custom ListView Adapter's `getView()` Method Get Called Multiple Times Before Scrolling?

Custom ListView Adapter's getView() Method Behavior

Question:

Why is the getView() method in a custom list adapter called multiple times in an apparently random order, even before any scrolling has occurred?

Answer:

The getView() method's order and frequency of calls are not guaranteed. When a ListView is laid out, it may measure a few children to determine its size. This can result in the creation and passing of "convertView" objects to getView() before any scrolling occurs.

In this specific case, using android:layout_height="wrap_content" for the ListView forces it to measure multiple children at layout time. This is generally not advisable and is considered a less efficient use of resources.

Understanding the ListView's Child Measurement Behavior:

ListView measures a fixed number of children (depending on the device and Android version) at layout time. This is done to determine its initial size. The number of measured children is then used for cache management and recycling.

Consequences of Inconsistent getView() Calls:

The inconsistent order and frequency of getView() calls can lead to performance issues and visual artifacts if not handled correctly. Proper implementation of the adapter's getView() method is crucial for efficient scrolling and a consistent user experience.

Best Practices:

To mitigate these issues, it is recommended to:

• Use android:layout_height="match_parent" for the ListView to ensure it scrolls correctly.
• Handle the case of convertView being null in getView(), as it may not be available even for visible rows.
• Optimize the getView() implementation to be as efficient as possible.

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