选择时如何更改 BottomNavigationBarItem 图标，Flutter

Question

我是 Flutter 新手。我有一个包含 4 个项目的 BottomNavigationBar。我想在按下时更改项目的图标。请帮忙

这是我目前所做的。

bottomNavigationBar : new BottomNavigationBar(
        currentIndex: index,
        onTap: (int index) {
          setState(() {
            this.index = index;
          }
          );
          _navigateToScreens(index);
        },
        type: BottomNavigationBarType.fixed,
        items: [
          new BottomNavigationBarItem(
              backgroundColor: Colors.white,
              icon: new Image.asset('images/1.0x/icon1.png'),
              title: new Text("Route1", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0))),
          new BottomNavigationBarItem(
              icon: new Image.asset('images/1.0x/icon2.png'),
              title: new Text("Route2", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0))),
          new BottomNavigationBarItem(
              icon: new Image.asset('images/1.0x/icon3.png'),
              title: new Text("Route3", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0),)),
          new BottomNavigationBarItem(
              icon: new Image.asset('images/1.0x/icon4.png'),
              title: new Text("Route4", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0),))
        ]);

Answer 1

您可以通过检查当前索引是否等于 BottomNavigationBarItem 索引的索引来更改图标。

具有静态索引值的简单示例：

bottomNavigationBar : new BottomNavigationBar(
        currentIndex: index,
        onTap: (int index) {
          setState(() {
            this.index = index;
          }
          );
          _navigateToScreens(index);
        },
        type: BottomNavigationBarType.fixed,
        items: [
          new BottomNavigationBarItem(
              backgroundColor: Colors.white,
              icon: index==0?new Image.asset('images/1.0x/icon1.png'):new Image.asset('images/1.0x/newIcon.png'),
              title: new Text("Route1", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0))),
          new BottomNavigationBarItem(
              icon: index==1?new Image.asset('images/1.0x/icon2.png'):new Image.asset('images/1.0x/newIcon.png'),
              title: new Text("Route2", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0))),
          new BottomNavigationBarItem(
              icon: index==2?new Image.asset('images/1.0x/icon3.png'):new Image.asset('images/1.0x/newIcon.png'),
              title: new Text("Route3", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0),)),
          new BottomNavigationBarItem(
              icon: index==3?new Image.asset('images/1.0x/icon4.png'):new Image.asset('images/1.0x/newIcon.png'),
              title: new Text("Route4", style: new TextStyle(
                  color: const Color(0xFF06244e), fontSize: 14.0),))
        ])

希望对您有所帮助！

Answer 2

如果您只想更改 BottomNavigationBarItem 图标的颜色，则不需要为一个图标设置两个不同颜色的图像。一个就够了。

您可以使用 ImageIcon 从自定义图像创建图标，并使用它的颜色属性来更改图标颜色，使用 currentIndex 的值，如下所示：

bottomNavigationBar: BottomNavigationBar(
    type: BottomNavigationBarType.fixed,
    currentIndex: currentTab,
    onTap: (int index) {
      setState(() {
        currentTab = index;
        currentPage = pages[index];
      });
    },
    items: <BottomNavigationBarItem>[
      BottomNavigationBarItem(
          icon: ImageIcon(
            AssetImage("assets/img/tab1.png"),
            color: currentTab == 0
                ? Colors.orange
                : Colors.black,
          ),
          title: Text('Title 1',
            style: TextStyle(
                fontSize: 10.0,
                color: currentTab == 0
                    ? Colors.orange
                    : Colors.black),
          )
      ),
      BottomNavigationBarItem(
          icon: ImageIcon(
            AssetImage("assets/img/tab2.png"),
            color: currentTab == 1
                ? Colors.orange
                : Colors.black,
          ),
          title: Text('Title 2',
            style: TextStyle(
                fontSize: 10.0,
                color: currentTab == 1
                    ? Colors.orange
                    : Colors.black),)
      ),
      BottomNavigationBarItem(
          icon: ImageIcon(
            AssetImage("assets/img/tab3.png"),
            color: currentTab == 2
                ? Colors.orange
                : Colors.black,
          ),
          title: Text('Title 3',
            style: TextStyle(
                fontSize: 10.0,
                color: currentTab == 2
                    ? Colors.orange
                    : Colors.black),)
      ),
      BottomNavigationBarItem(
          icon: ImageIcon(
            AssetImage("assets/img/tab4.png"),
            color: currentTab == 3
                ? Colors.orange
                : Colors.black,
          ),
          title: Text('Title 4',
            style: TextStyle(
                fontSize: 10.0,
                color: currentTab == 3
                    ? Colors.orange
                    : Colors.black),)
      )
    ],
  ),

希望有人会觉得这很有用。

Answer 3

Flutter 中的 BottomNavigationBarItem 添加了新功能 active icon。我们可以用它来判断选项卡处于活动状态时应该显示什么图标

bottomNavigationBar : new BottomNavigationBar(
    currentIndex: index,
    onTap: (int index) {
      setState(() {
        this.index = index;
      }
      );
      _navigateToScreens(index);
    },
    type: BottomNavigationBarType.fixed,
    items: [
      new BottomNavigationBarItem(
          backgroundColor: Colors.white,
          icon: new Image.asset('images/1.0x/icon1.png'),
          activeIcon:new Image.asset('images/1.0x/newIcon.png'),
          title: new Text("Route1", style: new TextStyle(
              color: const Color(0xFF06244e), fontSize: 14.0))),
      new BottomNavigationBarItem(
          icon: new Image.asset('images/1.0x/icon2.png'),
          activeIcon:new Image.asset('images/1.0x/newIcon.png'),
          title: new Text("Route2", style: new TextStyle(
              color: const Color(0xFF06244e), fontSize: 14.0))),
      new BottomNavigationBarItem(
          icon: new Image.asset('images/1.0x/icon3.png'),
          activeIcon: new Image.asset('images/1.0x/newIcon.png'),
          title: new Text("Route3", style: new TextStyle(
              color: const Color(0xFF06244e), fontSize: 14.0),)),
      new BottomNavigationBarItem(
          icon: new Image.asset('images/1.0x/icon4.png'),
          activeIcon: new Image.asset('images/1.0x/newIcon.png'),
          title: new Text("Route4", style: new TextStyle(
              color: const Color(0xFF06244e), fontSize: 14.0),))
    ]),

希望有人会觉得这有用。

Answer 4

如果有人正在寻找更改底部导航栏项目颜色的解决方案，当 "type" 设置为 "shifting" 时，请尝试一下：

type: BottomNavigationBarType.shifting,
  items: [
    BottomNavigationBarItem(
      activeIcon: Icon(
          Icons.home,
          color: Colors.grey[700],
        ),
      icon: Icon(
          Icons.home,
          color: Colors.grey,
        ),
      title: Text(
        'Home',
        style: TextStyle(
          color: Colors.grey[600]
          ),
        ),
    ),

Answer 5

如果您只想更改颜色而不是图标本身，fixedColor 确定图标被选中时的颜色：

BottomNavigationBar(
        ...
        fixedColor: Colors.red,
        ...
)

Answer 6

我是这样解决的。在 BottomNavigationBar 处，有两个属性 selectedItemColor 和 unselectedItemColor

bottomNavigationBar: BottomNavigationBar(
    ...
    selectedItemColor: Theme.of(context).primaryColor,
    unselectedItemColor: Theme.of(context).secondaryHeaderColor,
    ...
    items: [
      BottomNavigationBarItem(
        icon: Icon(Icons.search),
        title: Text('Search'),
      ),
      BottomNavigationBarItem(
        icon: Icon(Icons.star),
        title: Text('Featured'),
      ),
   ],
  ),

Answer 7

2020

Image

2 路

目前更好的方法是：

    selectedItemColor: Colors.white,
    unselectedItemColor: Color(0xFFF434A50),
    items: <BottomNavigationBarItem>[
        BottomNavigationBarItem(
            icon: ImageIcon(AssetImage("assets/tab1.png"),),
            title: Text('Agents'),
        ),
    ]

替代方式：

BottomNavigationBarItem(
   activeIcon: Image.asset("assets/tab1.png",width: 15,color: Colors.white,),
   icon: Image.asset("assets/tab1.png",width: 15,color: Color(0xFFF434A50),),
   title: Text('Agents'),
 ),

activeIcon - Selected tab

icon - Deselected tab

Answer 8

如果您显示来自图像资源的图标，则以这种方式更改底部导航栏的活动图标：

BottomNavigationBarItem(
              activeIcon: Image.asset(
                'assets/images/useractive.png',
                height: 25,
                width: 25,
              ),
              icon: Image.asset(
                'assets/images/user.png',
                height: 25,
                width: 25,
              ),
              title: Text('My Time Out')
),

Answer 9

color: _selectedIndex == ThisIndex?SelectedColor:normalColor,

Answer 10

只想添加到现有答案中：虽然 fixedColor、(un)selectedItemColor 是可行的方法，但有一个陷阱：

它们将被 BottomNavigationBarItem.icon.color 覆盖！

因此，请务必先去除硬编码的图标颜色。

选择时如何更改 BottomNavigationBarItem 图标，Flutter

How to change BottomNavigationBarItem icon when selected, Flutter

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