o2oa-cairong-android/o2_flutter/lib/common/widgets/mind_map_end_float_location.dart

import 'dart:math' as math;
import 'package:flutter/material.dart';

class MindMapFloatingActionButtonLocation extends FloatingActionButtonLocation {
  const MindMapFloatingActionButtonLocation();
  @override
  Offset getOffset(ScaffoldPrelayoutGeometry scaffoldGeometry) {
    // Compute the x-axis offset.
    final double fabX = _endOffset(scaffoldGeometry);

    // Compute the y-axis offset.
    final double contentBottom = scaffoldGeometry.contentBottom;
    final double bottomSheetHeight = scaffoldGeometry.bottomSheetSize.height;
    final double fabHeight = scaffoldGeometry.floatingActionButtonSize.height;
    final double snackBarHeight = scaffoldGeometry.snackBarSize.height;

    double fabY = contentBottom - fabHeight - kFloatingActionButtonMargin;
    if (snackBarHeight > 0.0) {
      fabY = math.min(
          fabY,
          contentBottom -
              snackBarHeight -
              fabHeight -
              kFloatingActionButtonMargin);
    }
    if (bottomSheetHeight > 0.0) {
      fabY =
          math.min(fabY, contentBottom - bottomSheetHeight - fabHeight / 2.0);
    }
    return Offset(fabX, fabY - 32);
  }

  double _endOffset(ScaffoldPrelayoutGeometry scaffoldGeometry,
      {double offset = 0.0}) {
    switch (scaffoldGeometry.textDirection) {
      case TextDirection.rtl:
        return _leftOffset(scaffoldGeometry, offset: offset);
      case TextDirection.ltr:
        return _rightOffset(scaffoldGeometry, offset: offset);
    }
  }

  double _leftOffset(ScaffoldPrelayoutGeometry scaffoldGeometry,
      {double offset = 0.0}) {
    return kFloatingActionButtonMargin +
        scaffoldGeometry.minInsets.left -
        offset;
  }

  double _rightOffset(ScaffoldPrelayoutGeometry scaffoldGeometry,
      {double offset = 0.0}) {
    return scaffoldGeometry.scaffoldSize.width -
        kFloatingActionButtonMargin -
        scaffoldGeometry.minInsets.right -
        scaffoldGeometry.floatingActionButtonSize.width +
        offset;
  }
}