line-chart-widget

linechartpainter-05.dart

  List<String> _computeLabels() {
    return _Y.map((yp) => "${yp.toStringAsFixed(1)}").toList();
  }

  void _drawYLabels(Canvas canvas, List<String> labels, List<Offset> points,
      double boxW, double top) {
    var i = 0;
    labels.forEach((label) {
      final dp = points[i];
      final dy = (dp.dy - 15.0) < top ? 15.0 : -15.0;
      final ly = dp + Offset(0, dy);
      drawTextCentered(canvas, ly, label, yLabelStyle, boxW);
      i++;
    });
  }

  void _drawXLabels(Canvas canvas, Offset c, double boxW) {
    _X.forEach((xp) {
      drawTextCentered(canvas, c, xp, xLabelStyle, boxW);
      c += Offset(boxW, 0);
    });
  }

  TextPainter measureText(
      String s, TextStyle style, double maxWidth, TextAlign align) {
    final span = TextSpan(text: s, style: style);
    final tp = TextPainter(
        text: span, textAlign: align, textDirection: TextDirection.ltr);
    tp.layout(minWidth: 0, maxWidth: maxWidth);
    return tp;
  }

  Size drawTextCentered(
      Canvas canvas, Offset c, String text, TextStyle style, double maxWidth) {
    final tp = measureText(text, style, maxWidth, TextAlign.center);
    final offset = c + Offset(-tp.width / 2.0, -tp.height / 2.0);
    tp.paint(canvas, offset);
    return tp.size;
  }