在机器人上添加打字指示器（颤振）

Question

我正在开发一个聊天机器人，我想在机器人回复用户之前添加一个打字指示器，我曾尝试在用户使用未来延迟输入消息后在小部件之间切换，但它根本不起作用。

以下代码演示了我如何尝试使用延迟的未来：

  bool _nextWidget = false;
  @override
  void initState() {
    super.initState();
  }

  void myMethod() {
    Future.delayed(
        const Duration(
          seconds: 5,
          milliseconds: 500,
        ),
            () {
          if (this.mounted) {
            setState(() {
              _nextWidget = true;
            });
          }
        });
  }

  Widget bot(String message)  {
    myMethod();
    return _nextWidget ?  botMessage(message) : botInd();
  }

  Widget botInd() {
    return Container(
        alignment: Alignment.bottomLeft,
        margin: EdgeInsets.only(top: 20),
        child: Container(
            constraints: BoxConstraints(maxWidth: 75, maxHeight: 100),
            child: JumpingDotsProgressIndicator(fontSize: 50.0, color: Colors.white)
        )
    );
  }

  Widget botMessage(String message) {
    return ChatBubble(
        clipper: ChatBubbleClipper2(type: BubbleType.receiverBubble),
        alignment: Alignment.bottomLeft,
        margin: EdgeInsets.only(top: 20),
        backGroundColor: Colors.white,
        child: Container(
            constraints: BoxConstraints(maxWidth: MediaQuery.of(context).size.width * 0.7),
            child: Text(
                message,
                style: TextStyle(color: Colors.black, fontWeight: FontWeight.bold)
            )
        )
    );
  }

Answer 1

查看https://flutter.dev/docs/cookbook/effects/typing-indicator，它解释了如何使用代码示例创建打字指示器的所有必要步骤。

import 'dart:math';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

void main() {
  runApp(
    const MaterialApp(
      home: ExampleIsTyping(),
      debugShowCheckedModeBanner: false,
    ),
  );
}

const _backgroundColor = Color(0xFF333333);

class ExampleIsTyping extends StatefulWidget {
  const ExampleIsTyping({
    Key? key,
  }) : super(key: key);

  @override
  _ExampleIsTypingState createState() => _ExampleIsTypingState();
}

class _ExampleIsTypingState extends State<ExampleIsTyping> {
  bool _isSomeoneTyping = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: _backgroundColor,
      appBar: AppBar(
        title: const Text('Typing Indicator'),
      ),
      body: Column(
        children: [
          Expanded(
            child: _buildMessages(),
          ),
          Align(
            alignment: Alignment.bottomLeft,
            child: TypingIndicator(
              showIndicator: _isSomeoneTyping,
            ),
          ),
          _buildIsTypingSimulator(),
        ],
      ),
    );
  }

  Widget _buildMessages() {
    return ListView.builder(
      padding: const EdgeInsets.symmetric(vertical: 8.0),
      itemCount: 25,
      reverse: true,
      itemBuilder: (context, index) {
        return Padding(
          padding: const EdgeInsets.only(left: 100.0),
          child: FakeMessage(isBig: index.isOdd),
        );
      },
    );
  }

  Widget _buildIsTypingSimulator() {
    return Container(
      color: Colors.grey,
      padding: const EdgeInsets.all(16),
      child: Center(
        child: CupertinoSwitch(
          onChanged: (newValue) {
            setState(() {
              _isSomeoneTyping = newValue;
            });
          },
          value: _isSomeoneTyping,
        ),
      ),
    );
  }
}

class TypingIndicator extends StatefulWidget {
  const TypingIndicator({
    Key? key,
    this.showIndicator = false,
    this.bubbleColor = const Color(0xFF646b7f),
    this.flashingCircleDarkColor = const Color(0xFF333333),
    this.flashingCircleBrightColor = const Color(0xFFaec1dd),
  }) : super(key: key);

  final bool showIndicator;
  final Color bubbleColor;
  final Color flashingCircleDarkColor;
  final Color flashingCircleBrightColor;

  @override
  _TypingIndicatorState createState() => _TypingIndicatorState();
}

class _TypingIndicatorState extends State<TypingIndicator>
    with TickerProviderStateMixin {
  late AnimationController _appearanceController;

  late Animation<double> _indicatorSpaceAnimation;

  late Animation<double> _smallBubbleAnimation;
  late Animation<double> _mediumBubbleAnimation;
  late Animation<double> _largeBubbleAnimation;

  late AnimationController _repeatingController;
  final List<Interval> _dotIntervals = const [
    Interval(0.25, 0.8),
    Interval(0.35, 0.9),
    Interval(0.45, 1.0),
  ];

  @override
  void initState() {
    super.initState();

    _appearanceController = AnimationController(
      vsync: this,
    )..addListener(() {
        setState(() {});
      });

    _indicatorSpaceAnimation = CurvedAnimation(
      parent: _appearanceController,
      curve: const Interval(0.0, 0.4, curve: Curves.easeOut),
      reverseCurve: const Interval(0.0, 1.0, curve: Curves.easeOut),
    ).drive(Tween<double>(
      begin: 0.0,
      end: 60.0,
    ));

    _smallBubbleAnimation = CurvedAnimation(
      parent: _appearanceController,
      curve: const Interval(0.0, 0.5, curve: Curves.elasticOut),
      reverseCurve: const Interval(0.0, 0.3, curve: Curves.easeOut),
    );
    _mediumBubbleAnimation = CurvedAnimation(
      parent: _appearanceController,
      curve: const Interval(0.2, 0.7, curve: Curves.elasticOut),
      reverseCurve: const Interval(0.2, 0.6, curve: Curves.easeOut),
    );
    _largeBubbleAnimation = CurvedAnimation(
      parent: _appearanceController,
      curve: const Interval(0.3, 1.0, curve: Curves.elasticOut),
      reverseCurve: const Interval(0.5, 1.0, curve: Curves.easeOut),
    );

    _repeatingController = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 1500),
    );

    if (widget.showIndicator) {
      _showIndicator();
    }
  }

  @override
  void didUpdateWidget(TypingIndicator oldWidget) {
    super.didUpdateWidget(oldWidget);

    if (widget.showIndicator != oldWidget.showIndicator) {
      if (widget.showIndicator) {
        _showIndicator();
      } else {
        _hideIndicator();
      }
    }
  }

  @override
  void dispose() {
    _appearanceController.dispose();
    _repeatingController.dispose();
    super.dispose();
  }

  void _showIndicator() {
    _appearanceController
      ..duration = const Duration(milliseconds: 750)
      ..forward();
    _repeatingController.repeat();
  }

  void _hideIndicator() {
    _appearanceController
      ..duration = const Duration(milliseconds: 150)
      ..reverse();
    _repeatingController.stop();
  }

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: _indicatorSpaceAnimation,
      builder: (context, child) {
        return SizedBox(
          height: _indicatorSpaceAnimation.value,
          child: child,
        );
      },
      child: Stack(
        children: [
          _buildAnimatedBubble(
            animation: _smallBubbleAnimation,
            left: 8,
            bottom: 8,
            bubble: _buildCircleBubble(8),
          ),
          _buildAnimatedBubble(
            animation: _mediumBubbleAnimation,
            left: 10,
            bottom: 10,
            bubble: _buildCircleBubble(16),
          ),
          _buildAnimatedBubble(
            animation: _largeBubbleAnimation,
            left: 12,
            bottom: 12,
            bubble: _buildStatusBubble(),
          ),
        ],
      ),
    );
  }

  Widget _buildAnimatedBubble({
    required Animation<double> animation,
    required double left,
    required double bottom,
    required Widget bubble,
  }) {
    return Positioned(
      left: left,
      bottom: bottom,
      child: AnimatedBuilder(
        animation: animation,
        builder: (context, child) {
          return Transform.scale(
            scale: animation.value,
            alignment: Alignment.bottomLeft,
            child: child,
          );
        },
        child: bubble,
      ),
    );
  }

  Widget _buildCircleBubble(double size) {
    return Container(
      width: size,
      height: size,
      decoration: BoxDecoration(
        shape: BoxShape.circle,
        color: widget.bubbleColor,
      ),
    );
  }

  Widget _buildStatusBubble() {
    return Container(
      width: 85,
      height: 44,
      padding: const EdgeInsets.symmetric(horizontal: 8),
      decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(27),
        color: widget.bubbleColor,
      ),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          _buildFlashingCircle(0),
          _buildFlashingCircle(1),
          _buildFlashingCircle(2),
        ],
      ),
    );
  }

  Widget _buildFlashingCircle(int index) {
    return AnimatedBuilder(
      animation: _repeatingController,
      builder: (context, child) {
        final circleFlashPercent =
            _dotIntervals[index].transform(_repeatingController.value);
        final circleColorPercent = sin(pi * circleFlashPercent);

        return Container(
          width: 12,
          height: 12,
          decoration: BoxDecoration(
            shape: BoxShape.circle,
            color: Color.lerp(widget.flashingCircleDarkColor,
                widget.flashingCircleBrightColor, circleColorPercent),
          ),
        );
      },
    );
  }
}

@immutable
class FakeMessage extends StatelessWidget {
  const FakeMessage({
    Key? key,
    required this.isBig,
  }) : super(key: key);

  final bool isBig;

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: const EdgeInsets.symmetric(vertical: 8.0, horizontal: 24.0),
      height: isBig ? 128.0 : 36.0,
      decoration: BoxDecoration(
        borderRadius: const BorderRadius.all(Radius.circular(8.0)),
        color: Colors.grey.shade300,
      ),
    );
  }
}