Handling large datasets with list builders

There is an interesting trick that mobile apps use when they need to render lists of data that can potentially contain more entries than your device has memory to display. This was especially critical in the early days of mobile app development, when phones were a lot less powerful than they are today. Imagine that you had to create a contacts app, where your user could potentially have hundreds and hundreds of scrollable contacts. If you put them all in a single ListView and asked Flutter to create all of these widgets, there would be a point where your app could run out of memory, slow down, and even crash.

Take a look at the contacts app on your phone and scroll up and down really fast. These apps don’t show any delay while scrolling, and they certainly aren’t in any danger of crashing because of the amount of data. What’s the secret? If you look carefully at your app, you’ll see that only so many items...