Detailed explanation of the use of IndexedStack in Flutter

IndexedStack is a layout component in Flutter, which is used to switch between multiple subcomponents and only display the current subcomponent. The following are detailed instructions on using IndexedStack:

1. Import IndexedStack:

import 'package:flutter/material.dart';

2. Create IndexedStack:

IndexedStack(
  index: 0, // 初始显示子组件的下标
  children: [
    // 子组件列表
    Container(color: Colors.blue),
    Container(color: Colors.green),
    Container(color: Colors.red),
  ],
),

3. Attribute analysis:

• index: Represents the subscript of the currently displayed subcomponent. For example, if the above is set to 0, the first subcomponent is displayed. If it is changed to 1, the second subcomponent is displayed.
• children: is a list that contains all the child components to be displayed by IndexedStack.

4. Implementation principle

The implementation principle of IndexedStack is actually very simple. It just hides other subcomponents when displaying a certain subcomponent. To achieve this function, Flutter internally implements a Stack and multiple Offstages.

• Stack: is a layout model of unlimited size, and its subcomponents can be stacked together. IndexedStack is actually a Stack.
• Offstage: It is used to hide a component, which can be achieved by setting its offstage property to true.

IndexedStack will set the offstage property of all subcomponents except the currently displayed subcomponents to true, so as to achieve the purpose of not displaying these subcomponents.

Precautions:

• IndexedStack will load all subcomponents at the same time, so if there are many subcomponents or occupy a large memory, this method may have an impact on performance.
• When it is necessary to dynamically switch subcomponents, it can be achieved by modifying the index, such as setting the index as a variable, and then modifying the variable when switching is required.