A brief understanding of the bottomNavigationBar property of the bottomNavigationBar property of the basic component Scaffold of Flutter

The bottomNavigationBar property is used to define the bottom navigation bar of the application. It is mainly composed of buttons and text. You can click the button to switch between different pages and display them in the bottom area of ​​the Scaffold.
The value of this property is the BottomNavigationBar type component. The BottomNavigationBar component includes the following table common properties.

property name	Types of	Function Description
currentIndex	int	Sets the current index value for the toggle button
fixedColor	Color	Set the color of the selected button, if not specified, use the system theme color
iconSize	double	Set button icon size
items	List	Set the bottom navigation bar button set, each item is a BottomNavigationBarItem, which consists of icon icon and title text attribute
onTap	ValueChanged	Set the callback event of pressing a button, you need to set the current index value according to the returned index value

Set the bottom navigation bar

/*设置底部导航栏*/
      bottomNavigationBar: BottomNavigationBar(
        items: <BottomNavigationBarItem>[
          BottomNavigationBarItem(
              icon: Icon(Icons.add_a_photo), title: Text('军机处')),
          BottomNavigationBarItem(
              icon: Icon(Icons.center_focus_strong), title: Text('血滴子')),
          BottomNavigationBarItem(
              icon: Icon(Icons.add_alarm_outlined), title: Text('大理寺'))
        ],
      ),

set click event

  /*设置单击事件*/
        onTap: (value){
    
    
          print(value);
        },

Test Click the three buttons below to output 0 1 2 respectively.



When the current index value is set to 1, select the second icon

 currentIndex: 1,