Flutter---JiBottomBar底部导航栏实现2

在Flutter---底部导航栏实现1中，底部导航栏使用BottomNavigationBar实现的，可能会有很多种情况，例如不想要BottomNavigationBar实现的效果，只想简单的变换即可，这时候就需要自定义了

先看效果

该效果使用Scaffold = PageView+JiBottomBar（自定义）

JiBottomBar代码：

import 'package:flutter/material.dart';

class JiBottomBar extends StatefulWidget {
  final List<JiBottomBarItem> items;
  final int currentIndex;
  final Color backgroundColor;
  final Color textFocusColor;
  final ValueChanged<int> onTap;

  JiBottomBar({
    @required this.items,
    this.currentIndex = 0,
    this.backgroundColor,
    this.textFocusColor,
    this.onTap,
  });

  @override
  _JiBottomBarState createState() {
    return new _JiBottomBarState();
  }
}

class _JiBottomBarState extends State<JiBottomBar>{
  @override
  Widget build(BuildContext context) {
    final List<Widget> children = <Widget>[];
    for (int i = 0; i < widget.items.length; i += 1) {
      children.add(_createItem(i));
    }

    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: children,
    );
  }

  Widget _createItem(int i) {
    JiBottomBarItem item = widget.items[i];
    bool selected = i == widget.currentIndex;
    return Expanded(
        flex: 1,
        child: Container(
          color: widget.backgroundColor,
          padding: EdgeInsets.only(top: 4, bottom: 4),
          child: InkResponse(
            onTap: (){
              if(widget.onTap != null){
                widget.onTap(i);
              }
            },
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              mainAxisSize: MainAxisSize.min,
              children: <Widget>[
                selected ? item.activeIcon : item.icon,
                DefaultTextStyle.merge(
                    style: TextStyle(
                      fontSize: 10,
                      // ignore: ambiguous_import
                      color: selected ? widget.textFocusColor : Colors.black38,
                    ),
                    child: item.title),
              ],
            ),
          ),
        ));
  }
}

class JiBottomBarItem {
  final Widget icon;
  final Widget activeIcon;
  final Widget title;

  JiBottomBarItem({@required this.icon, this.title, this.activeIcon})
      : assert(icon != null);
}

关键点：

1._createItem方法是创建每一个tab,用Expanded包裹，为了填充平分布局
2.内部使用了InkResponse，为了实现onTap点击事件，如果想要点击效果等，都可以使用该InkResponse实现
3.DefaultTextStyle.merge，之所以使用这个，是因为JiBottomBarItem中的title是一个widget,这时候想要实现选中高亮颜色，就需要使用该控件，并且在TextStyle中定义颜色即可，但是如果传入title的widget已经设置了颜色，或者字体大小，这里就不生效了

具体效果代码：

import 'package:flutter/material.dart';
import 'package:flutter_app/indicator/indicator.dart';
import 'home_page.dart';
import 'find_page.dart';
import 'msg_page.dart';
import 'my_page.dart';

class JiContainerPage extends StatefulWidget {
  @override
  _JiContainerPageState createState() {
    return new _JiContainerPageState();
  }
}

class _JiContainerPageState extends State<JiContainerPage>
    with SingleTickerProviderStateMixin {
  final PageController _pageController = new PageController(initialPage: 0);
  int _tabIndex = 0;

  _onPageChange(int index) {
    setState(() {
      _tabIndex = index;
    });
  }

  Image _getBarIcon(int index, bool isActive) {
    if (index == 0) {
      return _getAssetIcon(
          isActive ? "images/ic_bar_home_ed.png" : "images/ic_bar_home.png");
    } else if (index == 1) {
      return _getAssetIcon(
          isActive ? "images/ic_bar_find_ed.png" : "images/ic_bar_find.png");
    } else if (index == 2) {
      return _getAssetIcon(isActive
          ? "images/ic_bar_notify_ed.png"
          : "images/ic_bar_notify.png");
    } else {
      return _getAssetIcon(
          isActive ? "images/ic_bar_me_ed.png" : "images/ic_bar_me.png");
    }
  }

  Image _getAssetIcon(String path) {
    return Image.asset(path, width: 24.0, height: 24.0);
  }

  Text _getBarText(int index) {
    if (index == 0) {
      return Text("首页", style: TextStyle(fontSize: 10));
    } else if (index == 1) {
      return Text("发现", style: TextStyle(fontSize: 10));
    } else if (index == 2) {
      return Text("消息", style: TextStyle(fontSize: 10));
    } else {
      return Text("我的", style: TextStyle(fontSize: 10));
    }
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
          body: PageView.builder(
            onPageChanged: _onPageChange,
            controller: _pageController,
            itemBuilder: (BuildContext context, int index) {
              if (index == 0) {
                return new JiHomePage("0000");
              } else if (index == 1) {
                return new JiFindPage("1111");
              } else if (index == 2) {
                return new JiMsgPage("2222");
              } else if (index == 3) {
                return new JiMyPage("3333");
              }
            },
            itemCount: 4,
          ),
          bottomNavigationBar: JiBottomBar(
              backgroundColor: Color(0xffEEEFF2),
              currentIndex: _tabIndex,
              textFocusColor: Colors.deepOrange,
              onTap: (index){
                _pageController.jumpToPage(index);
//            _pageController.animateToPage(index, duration: Duration(milliseconds: 100), curve: Curves.ease);
                _onPageChange(index);
              },
              items: <JiBottomBarItem>[
                JiBottomBarItem(
                    icon: _getBarIcon(0, false),
                    title: _getBarText(0),
                    activeIcon: _getBarIcon(0, true)),
                JiBottomBarItem(
                    icon: _getBarIcon(1, false),
                    title: _getBarText(1),
                    activeIcon: _getBarIcon(1, true)),
                JiBottomBarItem(
                    icon: _getBarIcon(2, false),
                    title: _getBarText(2),
                    activeIcon: _getBarIcon(2, true)),
                JiBottomBarItem(
                    icon: _getBarIcon(3, false),
                    title: _getBarText(3),
                    activeIcon: _getBarIcon(3, true)),
              ])),
    );
  }
}

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