flutter - 如何在Flutter中实现多个倒计时进度条？

Question

如何在顶部实现 instagram 的故事进度条。如果存在多个故事，则为多个条形图；如果只有一个，则只有一个条形图。一个 10 秒的计时器。到目前为止，我所做的有点奏效，但当有 2 个或更多快照时它不起作用。

代码

Container(
    height: 30,
    margin: EdgeInsets.only(top: 50.0),
    child: CustomPaint(
        foregroundPainter: ProgressPainter(value: (this._totalTime) / 10.0 / widget.posts.length),
    ),
)

我尝试将它放入 ListView 中，但它有点不起作用。

更新:

我想到了一个“Row.builder”hack，但我怎样才能使进度动画化？我正在使用 countdown作为计时器解决方案，我可以在计时器结束时更改快照，但进度条正确更新是问题所在。

Row(
  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
  children: List.generate(widget.posts.length, (index) {
    if (this._index == index) {
      return Expanded(
        child: Container(
          padding: EdgeInsets.symmetric(horizontal: 10.0),
          height: 30,
          child: CustomPaint(
            foregroundPainter: ProgressPainter(value: this._countDown.remainingTime.inSeconds / 10.0),
          ),
        ),
      );
    } else {
      return Expanded(
        child: Container(
          padding: EdgeInsets.symmetric(horizontal: 10.0),
          height: 30,
          child: CustomPaint(
            foregroundPainter: ProgressPainter(value: 0.0),
          ),
        ),
      );
    }
  }).reversed.toList(),
)

注意事项: 我有进度条的效果，但只适用于一个。我有 2 个帖子，但只有一个进度条有效，其他仍然为 0。

Answer 1

解决了。

倒计时:

int _index = 0;
CountDown _countDown;
StreamSubscription _countDownSubscription;

@override
void initState() {
  super.initState();
  this._initTimer();
}

_initTimer() {
  if (mounted)
    setState(() {
      this._countDown = CountDown(Duration(seconds: widget.posts[this._index].timer));
      this._countDown.remainingTime = Duration(seconds: widget.posts[this._index].timer);
      this._countDownSubscription = this._countDown.stream.listen(null);
    });

  this._countDownSubscription.onData((d) {
    setState(() {}); // Updates the UI to animate the progress bar
  });

  this._countDownSubscription.onDone(() {
    if (widget.posts.length == this._index + 1) {
      Navigator.of(context).pop();
    } else {
      if (mounted)
        setState(() {
          this._index++;
          this._initTimer();
        });
    }
  });
}

进度条:

class ProgressPainter extends CustomPainter {
  final double value;

  ProgressPainter({this.value});

  Paint backgroundPaint = Paint()
    ..color = Colors.white
    ..style = PaintingStyle.stroke
    ..strokeCap = StrokeCap.round
    ..strokeWidth = 10;

  Paint valuePaint = Paint()
    ..color = Colors.deepPurple
    ..style = PaintingStyle.stroke
    ..strokeCap = StrokeCap.round
    ..strokeWidth = 10;

  @override
  void paint(Canvas canvas, Size size) {
    Path backgroundPath = Path();
    Path valuePath = Path();

    backgroundPath.moveTo(0, size.height / 2);
    backgroundPath.lineTo(size.width, size.height / 2);

    valuePath.moveTo(0, size.height / 2);
    valuePath.lineTo(size.width * this.value, size.height / 2);

    canvas.drawPath(backgroundPath, backgroundPaint);
    canvas.drawPath(valuePath, valuePaint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}

进度条的动态数量:

Row(
  mainAxisAlignment: MainAxisAlignment.spaceEvenly,
  children: List.generate(widget.posts.length, (index) {
    if (this._index == index) { // Current active post
      return Expanded(
        child: Container(
          padding: EdgeInsets.symmetric(horizontal: 10.0),
          child: CustomPaint(
            foregroundPainter: ProgressPainter(value: this._countDown.remainingTime.inSeconds / 10.0),
          ),
        ),
      );
    } else if (this._index > index) { // when it's done
      return Expanded(
        child: Container(
          padding: EdgeInsets.symmetric(horizontal: 10.0),
          child: CustomPaint(
            foregroundPainter: ProgressPainter(value: 0.0),
          ),
        ),
      );
    } else { // When it's next
      return Expanded(
        child: Container(
          padding: EdgeInsets.symmetric(horizontal: 10.0),
          child: CustomPaint(
            foregroundPainter: ProgressPainter(value: 1.0),
          ),
        ),
      );
    }
  }).reversed.toList(),
)

如果你们有更好更简单的解决方案，我完全赞成。