如何在 flutter 中的滚动 controller 中途调用 function

Question

I have a GridView that loads lazily at the end of the scroll controller, however I want to load the data when I reach halfway through the scroll controller. If I try to do an if statement that checks if the scroll has reached 50% of the controller it will never become equal, however, if I do a greater than equal to 50% it calls the function multiple times ending in duplicates of data. How can I avoid this duplication or is there a better way to do this.

Answer 1

A simple way to do it is just use your current code and an additional boolean 'wasCalled' which you set to true in the function. But: I'm confident there's better solutions.

I haven't really worked with GridViews, but as far as I understand it builds its children lazily. Have you tried inserting a custom widget in the middle of the children's list?

Eg in your build function you could:

@override
Widget build(BuildContext _) {
  callCustomFunction();
  return Container();
}

Answer 2

You can use the "extentAfter" property to know how much more space is left till the end..

I guess this is something you are trying to do..

https://stackoverflow.com/a/49509349/13460232