How to change BottomNavigationBarItem icon when selected, Flutter

If anyone is looking for a solution to change the Bottom Navigation Bar Item's color,when "type" is set to "shifting", then give this a try:

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]
          ),
        ),
    ),

You can change the icon by checking for the current index is equal to the index of BottomNavigationBarItem index.

Simple example with static index values:

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),))
        ])

Hope that helps!

There is new feature added in flutter in BottomNavigationBarItem that is active icon. we can use it to tell what should be the icon when a tab is active

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),))
    ]),

Hope someone will find this useful.