我有一个由custompainter制作的简单图表，我还使用了一个可触摸的库来检测触摸，但我不知道如何让它在用户触摸时重新绘制或绘制矩形。
尝试的方法：

• 点击后直接绘制

onTapDown: (details) {
          //display details
          toolTipDisplay = true;
          toolTipPos =
              Offset(details.globalPosition.dx, details.globalPosition.dy);
          canvas.drawRect(
              Rect.fromLTRB(toolTipPos.dx, toolTipPos.dy, 100, 100), paint);
        },

这将导致错误Unhandled Exception: Bad state: A Dart object attempted to access a native peer, but the native peer has been collected (nullptr). This is usually the result of calling methods on a native-backed object when the native resources have already been disposed.

• 尝试在onTap Func中设置要更改的变量，并在paint Func上绘制它。单击时不绘制任何内容。

下面是油漆工的油漆功能：

void paint(Canvas canvas, Size size) {
        //turn canvas to canvas with hittest
        touchable.TouchyCanvas touchCanvas =
            touchable.TouchyCanvas(context, canvas);
    
        // calculate series
        // 20% empty space
        // 80% series
        double seriesWidth = chartWidth / barData[0].valueList.length;
        double seriesLeft = chartLeft;
    
        // and then work on adding the height of the bars
    
        barData.asMap().forEach((index, series) {
             paintBars(seriesWidth, seriesLeft, series, maxY, chartHeight, touchCanvas,
              redPaint, index);
        });
    
        Paint linePaint = Paint();
        linePaint.color = Colors.red;
        linePaint.strokeWidth = 3;
        lineData.asMap().forEach((index, series) {
            paintLines(seriesWidth, seriesLeft, series, maxY, chartHeight,
              touchCanvas, linePaint, index);
        });
    
        // axis titles
        // xTitle
        if (xAxisTitle != null) {
            paintXAxisTitle(chartLeft, chartWidth, chartHeight, size, canvas);
        }
        // yTitle
        if (yAxisTitle != null) {
            paintYAxisTitle(chartLeft, size, chartHeight, canvas);
        }
        paintXTitles(seriesLeft, seriesWidth, chartHeight, size, canvas);
        paintYTitles(
            nextUnit, maxY, chartHeight, size, chartWidth, canvas, blackPaint);
    
        //display tooltip
        if (toolTipDisplay) {
            Paint toolTipPaint = Paint();
            toolTipPaint.color = Colors.blue;
            canvas.drawRRect(
                RRect.fromLTRBR(
                    toolTipPos.dx, toolTipPos.dy, 100, 100, Radius.circular(20)),
                toolTipPaint);
        }
    }

onTap函数位于paintLines和paintBars内部。