Flutter Lesson 9 Common list components
In mobile application development, lists are one of the most common ways to display data. Contacts, products, or news feeds require efficient and flexible list components. Flutter offers a powerful set of list widgets that allow you to design beautiful, high-performance interfaces.
Basic ListView and constructors
ListView is the simplest widget for organizing items in a linear direction. You can pass a list of children directly when the number of items is small. For long lists, ListView.builder is recommended, which builds items on demand using itemBuilder and itemCount, significantly improving performance.
Key parameters of ListView.builder
itemCount determines the defined length of the list. itemBuilder receives the index and must return the widget for that position. physics controls scroll behavior. shrinkWrap decides whether the list size adjusts to its content.
Other useful variants
ListView.separated allows adding separators between items, ideal for visual dividers. ListView.custom offers full control through SliverChildBuilderDelegate or SliverChildListDelegate for complex scenarios.
Scroll control
ScrollController allows you to control scrolling programmatically, animating to specific positions and listening to scroll events. Remember to dispose the controller in dispose, and you can use keepScrollOffset or PageStorageKey to restore positions after screen changes or rotations.
List items ListTile and variants
ListTile is a Material-style component that includes leading, title, subtitle, and trailing. There are variants such as CheckboxListTile, RadioListTile, and SwitchListTile for cases where an integrated control is needed in the list item.
Custom items
When ListTile is not enough, you can build custom items with Container, Row, Column, and ClipRRect to control images, text, ratings, and price. Keep the build clean and extract each item into an independent widget to reduce unnecessary rebuilds.
GridView and grid layouts
GridView is used for image galleries and product grids. GridView.count allows setting a fixed number of columns per row. GridView.builder is the option for many items using SliverGridDelegateWithFixedCrossAxisCount or SliverGridDelegateWithMaxCrossAxisExtent. GridView.extent allows specifying the maximum width of each cell and automatically adapting to different screen sizes.
Pull to refresh and RefreshIndicator
RefreshIndicator is the recommended widget for pull to refresh in Material applications. It requires an onRefresh callback that returns a Future, and when finished, the loading animation stops the indicator.
Scroll listening and infinite scroll
To implement infinite loading, use ScrollController and listen to the addListener event. Check if the scroll position is near the end to trigger loading more data, show a loading indicator while requesting information, and update the list when finished.
Position restoration
To preserve scroll position between navigations, use keepScrollOffset on ScrollController and PageStorageKey on the ListView when items change dynamically. This improves the experience when returning to an already explored list.
Performance optimization
Choosing the right constructor is essential. Extract items into independent widgets, use const when possible, and avoid expensive operations inside build such as complex calculations or network requests. Optimize images using appropriate sizes, caching, and caching libraries for network images. For frequently redrawn items, use RepaintBoundary to limit repaints.
Image best practices
Use appropriately sized image versions to avoid downscaling at render time. Implement caching and consider pausing image downloads while the user scrolls the list and resuming them when stopped.
Product app example
A common case is an app that allows toggling between grid view and list view with pull to refresh and infinite loading. The typical architecture includes state management for the product listing, ScrollController to detect the end, and asynchronous functions that simulate or execute network requests to load data pages.
Tips for building the UI
Use Card and ClipRRect to present images with rounded corners. Display price, rating, and description clearly. In grid mode, use childAspectRatio to control the proportion of each cell, and in list mode use ListTile or custom items for a richer experience.
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