add slider demo and fix bug

Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/gallery/demos.cs

                     buildRoute: (BuildContext context) => new SelectionControlsDemo()
                 ),
                 new GalleryDemo(
+                    title: "Sliders",
+                    subtitle: "Widgets for selecting a value by swiping",
+                    icon: GalleryIcons.sliders,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: SliderDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Slider-class.html",
+                    buildRoute: (BuildContext context) => new SliderDemo()
+                ),
+                new GalleryDemo(
                     title: "Dialogs",
                     subtitle: "Simple, alert, and fullscreen",
                     icon: GalleryIcons.dialogs,

com.unity.uiwidgets/Runtime/material/range_slider.cs

     }
 
 
-    class _RangeSliderState : SingleTickerProviderStateMixin<RangeSlider> {
+    class _RangeSliderState : TickerProviderStateMixin<RangeSlider> {
         static readonly TimeSpan enableAnimationDuration = new TimeSpan(0, 0, 0, 0, 75);
         static readonly TimeSpan valueIndicatorAnimationDuration = new TimeSpan(0, 0, 0, 0, 100);
 
         float _discretize(float value) {
             float result = value.clamp(0.0f, 1.0f);
             if (isDiscrete) {
-                result = (result * divisions.Value).round() / divisions.Value;
+                result = (result * divisions.Value).round() * 1.0f / divisions.Value;
             }
 
             return result;
             );
         }
 
-        void paint(PaintingContext context, Offset offset) {
+        public override void paint(PaintingContext context, Offset offset) {
             float startValue = _state.startPositionController.value;
             float endValue = _state.endPositionController.value;
 

Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/slider_demo.cs

+using System.Collections.Generic;
+using uiwidgets;
+using UIWidgetsGallery.gallery;
+using Unity.UIWidgets.animation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.service;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using UnityEngine;
+using Canvas = Unity.UIWidgets.ui.Canvas;
+using Color = Unity.UIWidgets.ui.Color;
+
+namespace UIWidgetsGallery.demo.material
+{
+    class SliderDemo : StatefulWidget {
+    public static readonly string routeName = "/material/slider";
+
+        public override State createState() => new _SliderDemoState();
+    }
+
+    static class SliderDemoUtils
+    {
+        public static Path _downTriangle(float size, Offset thumbCenter, bool invert = false) {
+     Path thumbPath = new Path();
+    float height = Mathf.Sqrt(3.0f) / 2.0f;
+    float centerHeight = size * height / 3.0f;
+    float halfSize = size / 2.0f;
+    float sign = invert ? -1.0f : 1.0f;
+    thumbPath.moveTo(thumbCenter.dx - halfSize, thumbCenter.dy + sign * centerHeight);
+    thumbPath.lineTo(thumbCenter.dx, thumbCenter.dy - 2.0f * sign * centerHeight);
+    thumbPath.lineTo(thumbCenter.dx + halfSize, thumbCenter.dy + sign * centerHeight);
+    thumbPath.close();
+    return thumbPath;
+    }
+
+    public static Path _rightTriangle(float size, Offset thumbCenter, bool invert = false) {
+    Path thumbPath = new Path();
+    float halfSize = size / 2.0f;
+    float sign = invert ? -1.0f : 1.0f;
+    thumbPath.moveTo(thumbCenter.dx + halfSize * sign, thumbCenter.dy);
+    thumbPath.lineTo(thumbCenter.dx - halfSize * sign, thumbCenter.dy - size);
+    thumbPath.lineTo(thumbCenter.dx - halfSize * sign, thumbCenter.dy + size);
+    thumbPath.close();
+    return thumbPath;
+    }
+
+    public static Path _upTriangle(float size, Offset thumbCenter) => _downTriangle(size, thumbCenter, invert: true);
+
+    public static Path _leftTriangle(float size, Offset thumbCenter) => _rightTriangle(size, thumbCenter, invert: true);
+    }
+    
+    class _CustomRangeThumbShape : RangeSliderThumbShape {
+     const float _thumbSize = 4.0f;
+     const float _disabledThumbSize = 3.0f;
+
+        public override Size getPreferredSize(bool isEnabled, bool isDiscrete) {
+        return isEnabled ? Size.fromRadius(_thumbSize) : Size.fromRadius(_disabledThumbSize);
+    }
+
+    static readonly Animatable<float> sizeTween = new FloatTween(
+    begin: _disabledThumbSize,
+    end: _thumbSize
+    );
+
+
+        public override void paint(
+            PaintingContext context,
+            Offset center,
+            Animation<float> activationAnimation = null,
+            Animation<float> enableAnimation = null,
+            bool isDiscrete = false,
+            bool isEnabled = false,
+            bool? isOnTop = null,
+            TextDirection? textDirection = null,
+            SliderThemeData sliderTheme = null,
+            Thumb? thumb = null
+        ) {
+     Canvas canvas = context.canvas;
+     ColorTween colorTween = new ColorTween(
+        begin: sliderTheme.disabledThumbColor,
+    end: sliderTheme.thumbColor
+    );
+
+    float size = _thumbSize * sizeTween.evaluate(enableAnimation);
+    Path thumbPath = null;
+        switch (textDirection) {
+        case TextDirection.rtl:
+        switch (thumb) {
+            case Thumb.start:
+                thumbPath = SliderDemoUtils._rightTriangle(size, center);
+                break;
+            case Thumb.end:
+                thumbPath = SliderDemoUtils._leftTriangle(size, center);
+                break;
+        }
+        break;
+        case TextDirection.ltr:
+        switch (thumb) {
+            case Thumb.start:
+                thumbPath = SliderDemoUtils._leftTriangle(size, center);
+                break;
+            case Thumb.end:
+                thumbPath = SliderDemoUtils._rightTriangle(size, center);
+                break;
+        }
+        break;
+    }
+    canvas.drawPath(thumbPath, new Paint{color = colorTween.evaluate(enableAnimation)});
+    }
+}
+    
+    class _CustomThumbShape : SliderComponentShape {
+    const float _thumbSize = 4.0f;
+    const float _disabledThumbSize = 3.0f;
+
+        public override Size getPreferredSize(bool isEnabled, bool isDiscrete, TextPainter textPainter) {
+        return isEnabled ? Size.fromRadius(_thumbSize) : Size.fromRadius(_disabledThumbSize);
+    }
+
+    static readonly Animatable<float> sizeTween = new FloatTween(
+    begin: _disabledThumbSize,
+    end: _thumbSize
+    );
+
+        public override void paint(
+            PaintingContext context,
+            Offset center,
+            Animation<float> activationAnimation = null,
+            Animation<float> enableAnimation = null,
+            bool isDiscrete = false,
+            TextPainter labelPainter = null,
+            RenderBox parentBox = null,
+            SliderThemeData sliderTheme = null,
+            TextDirection? textDirection = null,
+            float? value = null) {
+     Canvas canvas = context.canvas;
+     ColorTween colorTween = new ColorTween(
+        begin: sliderTheme.disabledThumbColor,
+    end: sliderTheme.thumbColor
+    );
+    float size = _thumbSize * sizeTween.evaluate(enableAnimation);
+    Path thumbPath = SliderDemoUtils._downTriangle(size, center);
+    canvas.drawPath(thumbPath, new Paint{color = colorTween.evaluate(enableAnimation)});
+    }
+} 
+    
+    class _CustomValueIndicatorShape : SliderComponentShape {
+     const float _indicatorSize = 4.0f;
+     const float _disabledIndicatorSize = 3.0f;
+     const float _slideUpHeight = 40.0f;
+
+        public override Size getPreferredSize(bool isEnabled, bool isDiscrete, TextPainter textPainter) {
+        return Size.fromRadius(isEnabled ? _indicatorSize : _disabledIndicatorSize);
+    }
+
+    static readonly Animatable<float> sizeTween = new FloatTween(
+    begin: _disabledIndicatorSize,
+    end: _indicatorSize
+    );
+
+        public override void paint(
+            PaintingContext context,
+            Offset center,
+            Animation<float> activationAnimation = null,
+            Animation<float> enableAnimation = null,
+            bool isDiscrete = false,
+            TextPainter labelPainter = null,
+            RenderBox parentBox = null,
+            SliderThemeData sliderTheme = null,
+            TextDirection? textDirection = null,
+            float? value = null){
+     Canvas canvas = context.canvas;
+     ColorTween enableColor = new ColorTween(
+        begin: sliderTheme.disabledThumbColor,
+    end: sliderTheme.valueIndicatorColor
+    );
+    
+            Tween<float> slideUpTween = new FloatTween(
+    begin: 0.0f,
+    end: _slideUpHeight
+    );
+     float size = _indicatorSize * sizeTween.evaluate(enableAnimation);
+     Offset slideUpOffset = new Offset(0.0f, -slideUpTween.evaluate(activationAnimation));
+     Path thumbPath = SliderDemoUtils._upTriangle(size, center + slideUpOffset);
+     Color paintColor = enableColor.evaluate(enableAnimation).withAlpha((255.0f * activationAnimation.value).round());
+    canvas.drawPath(
+    thumbPath,
+    new Paint{color = paintColor}
+    );
+            canvas.drawLine(
+                center,
+                center + slideUpOffset,
+                new Paint
+                {
+                    color = paintColor,
+                    style = PaintingStyle.stroke,
+                    strokeWidth = 2.0f
+                });
+    labelPainter.paint(canvas, center + slideUpOffset + new Offset(-labelPainter.width / 2.0f, -labelPainter.height - 4.0f));
+    }
+}
+    
+    class _SliderDemoState : State<SliderDemo> {
+        public override Widget build(BuildContext context) {
+        List<ComponentDemoTabData> demos = new List<ComponentDemoTabData>{
+        new ComponentDemoTabData(
+            tabName: "SINGLE",
+            description: "Sliders containing 1 thumb",
+            demoWidget: new _Sliders(),
+            documentationUrl: "https://docs.flutter.io/flutter/material/Slider-class.html"
+        ),
+        new ComponentDemoTabData(
+                tabName: "RANGE",
+                description: "Sliders containing 2 thumbs",
+                demoWidget: new _RangeSliders(),
+                documentationUrl: "https://docs.flutter.io/flutter/material/RangeSlider-class.html"
+            )
+            };
+
+        return new TabbedComponentDemoScaffold(
+            title: "Sliders",
+            demos: demos,
+            isScrollable: false,
+            showExampleCodeAction: false
+        );
+    }
+    }
+    
+    class _Sliders : StatefulWidget {
+        public override State createState() => new _SlidersState();
+    }
+    
+    class _SlidersState : State<_Sliders> {
+  float _continuousValue = 25.0f;
+        float _discreteValue = 20.0f;
+        float _discreteCustomValue = 25.0f;
+
+
+  public override Widget build(BuildContext context) {
+    ThemeData theme = Theme.of(context);
+    return new Padding(
+      padding:  EdgeInsets.symmetric(horizontal: 40.0f),
+      child: new Column(
+        mainAxisAlignment: MainAxisAlignment.spaceAround,
+        children: new List<Widget>{
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              new SizedBox(
+                  width: 64,
+                  height: 48,
+                  child: new TextField(
+                    textAlign: TextAlign.center,
+                    onSubmitted: (string value) => {
+                      float.TryParse(value, out float newValue);
+                      if (newValue != null && newValue != _continuousValue) {
+                        setState(() => {
+                          _continuousValue = newValue.clamp(0.0f, 100.0f);
+                        });
+                      }
+                    },
+                    keyboardType: TextInputType.number,
+                    controller: new TextEditingController(
+                      text: $"{_continuousValue:F0}"
+                    )
+                  )
+              ),
+              Slider.adaptive(
+                value: _continuousValue,
+                min: 0.0f,
+                max: 100.0f,
+                onChanged: (float value) => {
+                  setState(() => {
+                    _continuousValue = value;
+                  });
+                }
+              ),
+              new Text("Continuous with Editable Numerical Value")
+            }
+          ),
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              Slider.adaptive(value: 0.25f, onChanged: null),
+              new Text("Disabled")
+            }
+          ),
+           new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              Slider.adaptive(
+                value: _discreteValue,
+                min: 0.0f,
+                max: 200.0f,
+                divisions: 5,
+                label: $"{_discreteValue.round()}",
+                onChanged: (float value) => {
+                  setState(() => {
+                    _discreteValue = value;
+                  });
+                }
+              ),
+              new Text("Discrete")
+            }
+          ),
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              new SliderTheme(
+                data: theme.sliderTheme.copyWith(
+                  activeTrackColor: Colors.deepPurple,
+                  inactiveTrackColor: theme.colorScheme.onSurface.withOpacity(0.5f),
+                  activeTickMarkColor: theme.colorScheme.onSurface.withOpacity(0.7f),
+                  inactiveTickMarkColor:  theme.colorScheme.surface.withOpacity(0.7f),
+                  overlayColor: theme.colorScheme.onSurface.withOpacity(0.12f),
+                  thumbColor: Colors.deepPurple,
+                  valueIndicatorColor: Colors.deepPurpleAccent,
+                  thumbShape: new _CustomThumbShape(),
+                  valueIndicatorShape: new _CustomValueIndicatorShape(),
+                  valueIndicatorTextStyle: theme.accentTextTheme.bodyText1.copyWith(color: theme.colorScheme.onSurface)
+                ),
+                child: new Slider(
+                  value: _discreteCustomValue,
+                  min: 0.0f,
+                  max: 200.0f,
+                  divisions: 5,
+                  label: $"{_discreteCustomValue.round()}",
+                  onChanged: (float value) => {
+                    setState(() => {
+                      _discreteCustomValue = value;
+                    });
+                  }
+                )
+              ),
+              new Text("Discrete with Custom Theme")
+            }
+          )
+        }
+      )
+    );
+  }
+}
+    
+    class _RangeSliders : StatefulWidget {
+    
+    public override State createState() => new _RangeSlidersState();
+    }
+    
+    class _RangeSlidersState : State<_RangeSliders> {
+  RangeValues _continuousValues = new RangeValues(25.0f, 75.0f);
+  RangeValues _discreteValues = new RangeValues(40.0f, 120.0f);
+  RangeValues _discreteCustomValues = new RangeValues(40.0f, 160.0f);
+
+  public override Widget build(BuildContext context) {
+    return new Padding(
+      padding: EdgeInsets.symmetric(horizontal: 40.0f),
+      child: new Column(
+        mainAxisAlignment: MainAxisAlignment.spaceAround,
+        children: new List<Widget>{
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              new RangeSlider(
+                values: _continuousValues,
+                min: 0.0f,
+                max: 100.0f,
+                onChanged: (RangeValues values) => {
+                  setState(() => {
+                    _continuousValues = values;
+                  });
+                }
+              ),
+              new Text("Continuous")
+            }
+          ),
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              new RangeSlider(values: new RangeValues(0.25f, 0.75f), onChanged: null),
+              new Text("Disabled")
+            }
+          ),
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              new RangeSlider(
+                values: _discreteValues,
+                min: 0.0f,
+                max: 200.0f,
+                //divisions: 5,
+                labels: new RangeLabels($"{_discreteValues.start.round()}", $"{_discreteValues.end.round()}"),
+                onChanged: (RangeValues values) => {
+                  setState(() => {
+                    _discreteValues = values;
+                  });
+                }
+              ),
+              new Text("Discrete")
+            }
+          ),
+          new Column(
+            mainAxisSize: MainAxisSize.min,
+            children: new List<Widget>{
+              new SliderTheme(
+                data: new SliderThemeData(
+                  activeTrackColor: Colors.deepPurple,
+                  inactiveTrackColor: Colors.black26,
+                  activeTickMarkColor: Colors.white70,
+                  inactiveTickMarkColor: Colors.black,
+                  overlayColor: Colors.black12,
+                  thumbColor: Colors.deepPurple,
+                  rangeThumbShape: new _CustomRangeThumbShape(),
+                  showValueIndicator: ShowValueIndicator.never
+                ),
+                child: new RangeSlider(
+                  values: _discreteCustomValues,
+                  min: 0.0f,
+                  max: 200.0f,
+                  divisions: 5,
+                  labels: new RangeLabels($"{_discreteCustomValues.start.round()}", $"{_discreteCustomValues.end.round()}"),
+                  onChanged: (RangeValues values) => {
+                    setState(() => {
+                      _discreteCustomValues = values;
+                    });
+                  }
+                )
+              ),
+              new Text("Discrete with Custom Theme")
+            }
+          )
+        }
+      )
+    );
+  }
+}
+}