Flutter：页面滚动，导航栏背景颜色过渡动画

记录：导航默认透明，页面发生滚动后，导航背景色由0-1，过渡到白色背景。

view

import 'package:ducafe_ui_core/ducafe_ui_core.dart';
import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:redone/common/index.dart';
import 'package:tdesign_flutter/tdesign_flutter.dart';
import 'index.dart';class SendRedPacketReceivePage extends GetView<SendRedPacketReceiveController> {const SendRedPacketReceivePage({super.key});// 头部Widget _buildHeader() {return <Widget>[TDImage(assetUrl: 'assets/chat/images/6.png', width: 750.w, height: 216.w,type: TDImageType.square,),<Widget>[SizedBox(height: 150.w,),TDImage(assetUrl: 'assets/chat/images/user.png', width: 130.w, height: 130.w,type: TDImageType.circle,),SizedBox(height: 20.w,),TextWidget.body('黄玲玲发出的红包', size: 32.sp, color: AppTheme.color333,weight: FontWeight.w600,),SizedBox(height: 10.w,),TextWidget.body('恭喜发财，大吉大利', size: 26.sp, color: AppTheme.color999,),SizedBox(height: 10.w,),<Widget>[TextWidget.body('8.88', size: 80.sp, color: AppTheme.primary,weight: FontWeight.w600,),SizedBox(width: 10.w,),TextWidget.body('元', size: 26.sp, color: AppTheme.primary,weight: FontWeight.w600,),].toRow(mainAxisAlignment: MainAxisAlignment.center,crossAxisAlignment: CrossAxisAlignment.baseline,textBaseline: TextBaseline.alphabetic),].toColumn()].toStack();}// 红包总数Widget _buildRedPacketCount() {return <Widget>[TextWidget.body('共10个红包，5秒钟抢完', size: 26.sp, color: AppTheme.color999,),].toRow().paddingHorizontal(30.w).height(68.w).backgroundColor(const Color(0xfff3f4f5)).clipRRect(all: 10.w);}// 红包列表Widget _buildRedPacketList() {return SliverList(delegate: SliverChildBuilderDelegate((BuildContext context, int index) {return <Widget>[TDImage(assetUrl: 'assets/chat/images/user.png',width: 84.w,height: 84.w, type: TDImageType.circle,),SizedBox(width: 20.w),<Widget>[TextWidget.body('黄玲玲', size: 30.sp,color: AppTheme.color333,),SizedBox(height: 10.w),TextWidget.body('2024-01-01 12:00',size: 24.sp,color: AppTheme.color999,),].toColumn(crossAxisAlignment: CrossAxisAlignment.start,).expanded(),TextWidget.body('0.88元',size: 30.sp,color: AppTheme.color333,),].toRow(crossAxisAlignment: CrossAxisAlignment.start).paddingVertical(20.w).decorated(border: const Border(bottom: BorderSide(width: 1, color: AppTheme.dividerColor),));},childCount: 15,),);}// 主视图Widget _buildView() {return CustomScrollView(controller: controller.scrollController,slivers: [_buildHeader().sliverToBoxAdapter(),SizedBox(height: 60.w,).sliverToBoxAdapter(),_buildRedPacketCount().sliverToBoxAdapter().sliverPaddingHorizontal(30.w),SizedBox(height: 20.w,).sliverToBoxAdapter(),_buildRedPacketList().sliverPaddingHorizontal(30.w),],);}@overrideWidget build(BuildContext context) {return GetBuilder<SendRedPacketReceiveController>(init: SendRedPacketReceiveController(),id: "send_red_packet_receive",builder: (_) {return Scaffold(backgroundColor: AppTheme.pageBgColor,body: <Widget>[_buildView(),AnimatedContainer(duration: const Duration(milliseconds: 100),color: Colors.white.withOpacity(controller.opacity),child: TDNavBar(height: 44,title: '领取红包',titleColor: AppTheme.color333.withOpacity(controller.opacity),titleFontWeight: FontWeight.w600,backgroundColor: Colors.transparent,screenAdaptation: true,useDefaultBack: true,),).positioned(left: 0, right: 0, top: 0),].toStack());},);}
}

controller

import 'package:get/get.dart';
import 'package:flutter/material.dart';class SendRedPacketReceiveController extends GetxController {SendRedPacketReceiveController();// 滚动控制器final ScrollController scrollController = ScrollController();// 渐变系数 0-1double opacity = 0.0;// 滚动开始变化的位置final double scrollStartPoint = 20.0;// 滚动结束变化的位置final double scrollEndPoint = 120.0;_initData() {update(["send_red_packet_receive"]);}@overridevoid onInit() {super.onInit();// 监听滚动scrollController.addListener(() {// 计算 0-1 之间的渐变系数double newOpacity;if (scrollController.offset <= scrollStartPoint) {// 开始点之前完全透明newOpacity = 0.0;} else if (scrollController.offset >= scrollEndPoint) {// 结束点之后完全不透明newOpacity = 1.0;} else {// 在开始点和结束点之间线性计算newOpacity = (scrollController.offset - scrollStartPoint) /  (scrollEndPoint - scrollStartPoint);// 确保值在0-1范围内并保留更多小数位精度newOpacity = double.parse(newOpacity.toStringAsFixed(3)).clamp(0.0, 1.0);}// 只有当透明度变化时才更新UIif ((opacity - newOpacity).abs() > 0.001) {opacity = newOpacity;update(["send_red_packet_receive"]);}});_initData();}@overridevoid onReady() {super.onReady();_initData();}@overridevoid onClose() {scrollController.dispose();super.onClose();}
}