颤抖跳过ListView或PageView中的子级

Question

Let's say I have 4 children in my PageView as

PageView(
  children: <Widget>[
    Page1(),
    Page2(),
    Page3(), // how to skip this when a condition is false
    Page4(),
  ],
)

I want to show Page3 when a bool value is true , how do I do that, I thought of putting a null but I am not allowed to do that.

Answer 1

One way to do is with - With sync* functions.

Page2 will be displayed if the condition is true.

bool condition = true;

PageView(
          children: List.unmodifiable(() sync* {
            yield Center(child: Text('Page1'));   //Page 1
            if (condition) {
              yield Center(child: Text('Page2'));  // Page2(conditional)
            }
            // yield* children;
            yield Center(child: Text('Page3'));  //Page3
          }()),
        ),

Answer 2

Seems like this is a better way to make the things happen.

List<Widget> list = [];
if (condition) {
  list = [
    Page1(),
    Page2(),
    Page3(), 
    Page4(),
  ];
} else {
  list = [
    Page1(),
    Page2(),
    Page4(),
  ];
}

return PageView(children: list);

Answer 3

Beginning with Dart 2.2.2, you can use normal if condition.

PageView(
  children: <Widget>[
    Page1(),
    Page2(),
    if (_condition) Page3(), // visible only when condition is true
    Page4(),
  ],
)