我正在尝试在应该创建音频波形的容器行顶部创建一个范围 slider ，但我什至不知道从哪里开始...

主要问题是范围 slider 位于容器行的正上方，它应该在“选定”部分更改它们的颜色。

这是我目前拥有的:

创建图像和细节的代码。

class BeatLyricsPage extends StatefulWidget {
  final Beat beat;
  BeatLyricsPage(this.beat);

  @override
  _BeatLyricsPageState createState() => _BeatLyricsPageState(beat);
}

class _BeatLyricsPageState extends State<BeatLyricsPage> {
  final Beat beat;


  final _kPicHeight = 190.0;
  // used in _buildPageHeading to add the beat key and beat bpm
  Widget _buildBeatInfoItem(String text) => DecoratedBox(
        decoration: BoxDecoration(
          border: Border.all(color: MyColor.white, width: 1.0),
          borderRadius: BorderRadius.circular(4.0),
        ),
        child: Padding(
          padding: EdgeInsets.symmetric(vertical: 3.0, horizontal: 12.0),
          child: Text(text, style: TextStyle(color: MyColor.white, fontSize: 10.0, fontWeight: FontWeight.w600)),
        ),
      );

  final _kAudioControlsWidth = 180.0;
  final _kAudioControlsHeight = 36.0;
  final _kAudioControlsMainButtonSize = 56.0;

  Widget _buildAudioControls(BuildContext context) => Positioned(
        left: (MediaQuery.of(context).size.width / 2) - (_kAudioControlsWidth / 2),
        top: _kPicHeight - (_kAudioControlsHeight / 2),
        child: Stack(
          overflow: Overflow.visible,
          children: [
            Container(
              width: _kAudioControlsWidth,
              height: _kAudioControlsHeight,
              decoration: BoxDecoration(color: MyColor.darkGrey, borderRadius: BorderRadius.circular(100.0)),
              padding: EdgeInsets.symmetric(horizontal: LayoutSpacing.sm),
              child: Row(
                children: [
                  CButtonLike(beatId: beat.id),
                  Spacer(),
                  GestureDetector(
                    behavior: HitTestBehavior.opaque,
                    child: Icon(BeatPulseIcons.cart),
                    onTap: () => Navigator.push(context, MaterialPageRoute(builder: (_) => LicenseOptionsPage(beat))),
                  ),
                ],
              ),
            ),
            // ****** MAIN BUTTON (Play/Pause) ******
            Positioned(
              left: (_kAudioControlsWidth / 2) - (_kAudioControlsMainButtonSize / 2),
              top: (_kAudioControlsHeight - _kAudioControlsMainButtonSize) / 2,
              child: Container(
                height: _kAudioControlsMainButtonSize,
                width: _kAudioControlsMainButtonSize,
                decoration: BoxDecoration(
                    gradient: LinearGradient(begin: Alignment.topLeft, colors: [MyColor.primary, Color(0xFFf80d0a)]),
                    borderRadius: BorderRadius.circular(100.0)),
                child: CButtonPlay(),
              ),
            )
          ],
        ),
      );

  Widget _buildWaveForm() {
    // creates a random list of doubles, "fake data"
    var rng = Random();
    final List waveFormData = [];
    for (var i = 0; i < 90; i++) {
      waveFormData.add(rng.nextInt(45).toDouble());
    }
    // player bloc
    final playerBloc = BlocProvider.getPlayerBloc(context);
    // renders
    return Container(
      height: _kPicHeight,
      padding: EdgeInsets.symmetric(vertical: LayoutSpacing.xxxl),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.end,
        children: [
          // current playing second
          StreamBuilder<double>(
            stream: playerBloc.playingSecond,
            initialData: 0.0,
            builder: (_, playingSecondSnapshot) {
              // current beat playing
              return StreamBuilder<Beat>(
                stream: playerBloc.playingBeat,
                builder: (_, playingBeatSnapshot) {
                  final playingBeat = playingBeatSnapshot.data;
                  // if the beat playing is the same as the beat selected for the lyrics, show playing seconds
                  if (playingBeat?.id == beat.id)
                    return Text(secondsToTime(playingSecondSnapshot.data), style: MyFontStyle.sizeXxs);
                  // otherwise show 0:00
                  else
                    return Text(secondsToTime(0), style: MyFontStyle.sizeXxs);
                },
              );
            },
          ),
          SizedBox(width: LayoutSpacing.xs),
          Row(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.end,
            children: waveFormData
                .map((waveFormDataIndex) => Container(
                      height: waveFormDataIndex > 5.0 ? waveFormDataIndex : 5.0,
                      width: 2,
                      color: MyColor.white,
                      margin: EdgeInsets.only(right: 1),
                    ))
                .toList(),
          ),
          SizedBox(width: LayoutSpacing.xs),
          Text(secondsToTime(beat.length), style: MyFontStyle.sizeXxs),
        ],
      ),
    );
  }

  Widget _buildPageHeading(BuildContext context, {@required String imageUrl}) => Stack(
        children: [
          Column(
            children: [
              Hero(
                tag: MyKeys.makePlayerCoverKey(beat.id),
                child: Opacity(
                  opacity: 0.3,
                  child: Container(
                    height: _kPicHeight,
                    decoration: BoxDecoration(
                      image: DecorationImage(image: CachedNetworkImageProvider(imageUrl), fit: BoxFit.cover),
                    ),
                  ),
                ),
              ),
              Container(color: MyColor.background, height: LayoutSpacing.xl)
            ],
          ),
          Padding(
            padding: EdgeInsets.all(LayoutSpacing.xs),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.end,
              children: [
                _buildBeatInfoItem(beat.key),
                SizedBox(width: 4.0),
                _buildBeatInfoItem('${beat.bpm} BPM'),
              ],
            ),
          ),
          _buildAudioControls(context),
          _buildWaveForm(),
        ],
      );
}

最佳答案

要创建自定义范围 slider ，您可以使用 GestureRecognizer并将每个 slider 的位置保存在 StatefulWidget 内的变量中.要确定索引为 i 的条是否在范围内，您可以将限制器的像素位置(bar1&bar2 划分为下面的来源)通过条的宽度并将其与 i 进行比较。

很遗憾，我无法使用您的代码示例。相反，我创建了一个最低限度的示例，如下所示。如果您花一点时间阅读，我相信您可以将其转移到您的应用程序中。

import 'dart:math';

import 'package:flutter/material.dart';

List<int> bars = [];

void main() {
  // generate random bars
  Random r = Random();
  for (var i = 0; i < 50; i++) {
    bars.add(r.nextInt(200));
  }

  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Home(),
    );
  }
}

class Home extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => HomeState();
}

class HomeState extends State<Home> {
  static const barWidth = 5.0;
  double bar1Position = 60.0;
  double bar2Position = 180.0;

  @override
  Widget build(BuildContext context) {
    int i = 0;

    return Scaffold(
      body: Center(
        child: Stack(
          alignment: Alignment.centerLeft,
          children: <Widget>[
            Row(
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisAlignment: MainAxisAlignment.start,
              children: bars.map((int height) {
                Color color =
                    i >= bar1Position / barWidth && i <= bar2Position / barWidth
                        ? Colors.deepPurple
                        : Colors.blueGrey;
                i++;

                return Container(
                  color: color,
                  height: height.toDouble(),
                  width: 5.0,
                );
              }).toList(),
            ),
            Bar(
              position: bar2Position,
              callback: (DragUpdateDetails details) {
                setState(() {
                  bar2Position += details.delta.dx;
                });
              },
            ),
            Bar(
              position: bar1Position,
              callback: (DragUpdateDetails details) {
                setState(() {
                  bar1Position += details.delta.dx;
                });
              },
            ),
          ],
        ),
      ),
    );
  }
}

class Bar extends StatelessWidget {
  final double position;
  final GestureDragUpdateCallback callback;

  Bar({this.position, this.callback});

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.only(left: position >= 0.0 ? position : 0.0),
      child: GestureDetector(
        onHorizontalDragUpdate: callback,
        child: Container(
          color: Colors.red,
          height: 200.0,
          width: 5.0,
        ),
      ),
    );
  }
}

关于dart - Flutter 自定义范围 slider ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52987440/