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Unverified Commit c2c64a5a authored by Greg Spencer's avatar Greg Spencer Committed by GitHub
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Add onChangeStart and onChangeEnd to slider. (#17298) 

This fixes #17169 by adding onChangeStart and onChangeEnd to the slider. These will be called when the user starts a change, and when they end a change, regardless of whether that change is a tap or a drag.

These differ from onChanged, in that they only report when the user starts and ends an interaction, not at every slight change.
parent 106231c0
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Showing with 155 additions and 3 deletions
packages/flutter/lib/src/material/slider.dart
View file @ c2c64a5a
......@@ -16,6 +16,9 @@ import 'material.dart';
import 'slider_theme.dart';
import 'theme.dart';
// Examples can assume:
// int _duelCommandment = 1;
/// A Material Design slider.
///
/// Used to select from a range of values.
......@@ -46,7 +49,8 @@ import 'theme.dart';
/// of the slider changes, the widget calls the [onChanged] callback. Most
/// widgets that use a slider will listen for the [onChanged] callback and
/// rebuild the slider with a new [value] to update the visual appearance of the
/// slider.
/// slider. To know when the value starts to change, or when it is done
/// changing, set the optional callbacks [onChangeStart] and/or [onChangeEnd].
///
/// By default, a slider will be as wide as possible, centered vertically. When
/// given unbounded constraints, it will attempt to make the track 144 pixels
......@@ -83,7 +87,12 @@ class Slider extends StatefulWidget {
/// the slider.
///
/// * [value] determines currently selected value for this slider.
/// * [onChanged] is called when the user selects a new value for the slider.
/// * [onChanged] is called while the user is selecting a new value for the
/// slider.
/// * [onChangeStart] is called when the user starts to select a new value for
/// the slider.
/// * [onChangeEnd] is called when the user is done selecting a new value for
/// the slider.
///
/// You can override some of the colors with the [activeColor] and
/// [inactiveColor] properties, although more fine-grained control of the
......@@ -92,6 +101,8 @@ class Slider extends StatefulWidget {
Key key,
@required this.value,
@required this.onChanged,
this.onChangeStart,
this.onChangeEnd,
this.min: 0.0,
this.max: 1.0,
this.divisions,
......@@ -111,7 +122,8 @@ class Slider extends StatefulWidget {
/// The slider's thumb is drawn at a position that corresponds to this value.
final double value;
/// Called when the user selects a new value for the slider.
/// Called during a drag when the user is selecting a new value for the slider
/// by dragging.
///
/// The slider passes the new value to the callback but does not actually
/// change state until the parent widget rebuilds the slider with the new
......@@ -123,6 +135,8 @@ class Slider extends StatefulWidget {
/// [StatefulWidget] using the [State.setState] method, so that the parent
/// gets rebuilt; for example:
///
/// ## Sample code
///
/// ```dart
/// new Slider(
/// value: _duelCommandment.toDouble(),
......@@ -137,8 +151,82 @@ class Slider extends StatefulWidget {
/// },
/// )
/// ```
///
/// See also:
///
/// * [onChangeStart] for a callback that is called when the user starts
/// changing the value.
/// * [onChangeEnd] for a callback that is called when the user stops
/// changing the value.
final ValueChanged<double> onChanged;
/// Called when the user starts selecting a new value for the slider.
///
/// This callback shouldn't be used to update the slider [value] (use
/// [onChanged] for that), but rather to be notified when the user has started
/// selecting a new value by starting a drag or with a tap.
///
/// The value passed will be the last [value] that the slider had before the
/// change began.
///
/// ## Sample code
///
/// ```dart
/// new Slider(
/// value: _duelCommandment.toDouble(),
/// min: 1.0,
/// max: 10.0,
/// divisions: 10,
/// label: '$_duelCommandment',
/// onChanged: (double newValue) {
/// setState(() {
/// _duelCommandment = newValue.round();
/// });
/// },
/// onChangeStart: (double startValue) {
/// print('Started change at $startValue');
/// },
/// )
/// ```
///
/// See also:
///
/// * [onChangeEnd] for a callback that is called when the value change is
/// complete.
final ValueChanged<double> onChangeStart;
/// Called when the user is done selecting a new value for the slider.
///
/// This callback shouldn't be used to update the slider [value] (use
/// [onChanged] for that), but rather to know when the user has completed
/// selecting a new [value] by ending a drag or a click.
///
/// ## Sample code
///
/// ```dart
/// new Slider(
/// value: _duelCommandment.toDouble(),
/// min: 1.0,
/// max: 10.0,
/// divisions: 10,
/// label: '$_duelCommandment',
/// onChanged: (double newValue) {
/// setState(() {
/// _duelCommandment = newValue.round();
/// });
/// },
/// onChangeEnd: (double newValue) {
/// print('Ended change on $newValue');
/// },
/// )
/// ```
///
/// See also:
///
/// * [onChangeStart] for a callback that is called when a value change
/// begins.
final ValueChanged<double> onChangeEnd;
/// The minimum value the user can select.
///
/// Defaults to 0.0. Must be less than or equal to [max].
......@@ -269,6 +357,16 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
}
}
void _handleDragStart(double value) {
assert(widget.onChangeStart != null);
widget.onChangeStart(_lerp(value));
}
void _handleDragEnd(double value) {
assert(widget.onChangeEnd != null);
widget.onChangeEnd(_lerp(value));
}
// Returns a number between min and max, proportional to value, which must
// be between 0.0 and 1.0.
double _lerp(double value) {
......@@ -313,6 +411,8 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
sliderTheme: sliderTheme,
mediaQueryData: MediaQuery.of(context),
onChanged: (widget.onChanged != null) && (widget.max > widget.min) ? _handleChanged : null,
onChangeStart: widget.onChangeStart != null ? _handleDragStart : null,
onChangeEnd: widget.onChangeEnd != null ? _handleDragEnd : null,
state: this,
);
}
......@@ -327,6 +427,8 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
this.sliderTheme,
this.mediaQueryData,
this.onChanged,
this.onChangeStart,
this.onChangeEnd,
this.state,
}) : super(key: key);
......@@ -336,6 +438,8 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
final SliderThemeData sliderTheme;
final MediaQueryData mediaQueryData;
final ValueChanged<double> onChanged;
final ValueChanged<double> onChangeStart;
final ValueChanged<double> onChangeEnd;
final _SliderState state;
@override
......@@ -348,6 +452,8 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
theme: Theme.of(context),
mediaQueryData: mediaQueryData,
onChanged: onChanged,
onChangeStart: onChangeStart,
onChangeEnd: onChangeEnd,
state: state,
textDirection: Directionality.of(context),
);
......@@ -363,6 +469,8 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
..theme = Theme.of(context)
..mediaQueryData = mediaQueryData
..onChanged = onChanged
..onChangeStart = onChangeStart
..onChangeEnd = onChangeEnd
..textDirection = Directionality.of(context);
// Ticker provider cannot change since there's a 1:1 relationship between
// the _SliderRenderObjectWidget object and the _SliderState object.
......@@ -378,6 +486,8 @@ class _RenderSlider extends RenderBox {
ThemeData theme,
MediaQueryData mediaQueryData,
ValueChanged<double> onChanged,
this.onChangeStart,
this.onChangeEnd,
@required _SliderState state,
@required TextDirection textDirection,
}) : assert(value != null && value >= 0.0 && value <= 1.0),
......@@ -540,6 +650,9 @@ class _RenderSlider extends RenderBox {
}
}
ValueChanged<double> onChangeStart;
ValueChanged<double> onChangeEnd;
TextDirection get textDirection => _textDirection;
TextDirection _textDirection;
set textDirection(TextDirection value) {
......@@ -633,6 +746,12 @@ class _RenderSlider extends RenderBox {
void _startInteraction(Offset globalPosition) {
if (isInteractive) {
_active = true;
// We supply the *current* value as the start location, so that if we have
// a tap, it consists of a call to onChangeStart with the previous value and
// a call to onChangeEnd with the new value.
if (onChangeStart != null) {
onChangeStart(_discretize(value));
}
_currentDragValue = _getValueFromGlobalPosition(globalPosition);
onChanged(_discretize(_currentDragValue));
_state.overlayController.forward();
......@@ -652,6 +771,9 @@ class _RenderSlider extends RenderBox {
void _endInteraction() {
if (_active && _state.mounted) {
if (onChangeEnd != null) {
onChangeEnd(_discretize(_currentDragValue));
}
_active = false;
_currentDragValue = 0.0;
_state.overlayController.reverse();
......
packages/flutter/test/material/slider_test.dart
View file @ c2c64a5a
......@@ -46,6 +46,8 @@ void main() {
testWidgets('Slider can move when tapped (LTR)', (WidgetTester tester) async {
final Key sliderKey = new UniqueKey();
double value = 0.0;
double startValue;
double endValue;
await tester.pumpWidget(
new Directionality(
......@@ -64,6 +66,12 @@ void main() {
value = newValue;
});
},
onChangeStart: (double value) {
startValue = value;
},
onChangeEnd: (double value) {
endValue = value;
},
),
),
),
......@@ -76,6 +84,10 @@ void main() {
expect(value, equals(0.0));
await tester.tap(find.byKey(sliderKey));
expect(value, equals(0.5));
expect(startValue, equals(0.0));
expect(endValue, equals(0.5));
startValue = null;
endValue = null;
await tester.pump(); // No animation should start.
expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
......@@ -85,6 +97,8 @@ void main() {
final Offset target = topLeft + (bottomRight - topLeft) / 4.0;
await tester.tapAt(target);
expect(value, closeTo(0.25, 0.05));
expect(startValue, equals(0.5));
expect(endValue, closeTo(0.25, 0.05));
await tester.pump(); // No animation should start.
expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
});
......@@ -138,7 +152,11 @@ void main() {
testWidgets("Slider doesn't send duplicate change events if tapped on the same value", (WidgetTester tester) async {
final Key sliderKey = new UniqueKey();
double value = 0.0;
double startValue;
double endValue;
int updates = 0;
int startValueUpdates = 0;
int endValueUpdates = 0;
await tester.pumpWidget(
new Directionality(
......@@ -158,6 +176,14 @@ void main() {
value = newValue;
});
},
onChangeStart: (double value) {
startValueUpdates++;
startValue = value;
},
onChangeEnd: (double value) {
endValueUpdates++;
endValue = value;
},
),
),
),
......@@ -170,11 +196,15 @@ void main() {
expect(value, equals(0.0));
await tester.tap(find.byKey(sliderKey));
expect(value, equals(0.5));
expect(startValue, equals(0.0));
expect(endValue, equals(0.5));
await tester.pump();
await tester.tap(find.byKey(sliderKey));
expect(value, equals(0.5));
await tester.pump();
expect(updates, equals(1));
expect(startValueUpdates, equals(2));
expect(endValueUpdates, equals(2));
});
testWidgets('Value indicator shows for a bit after being tapped', (WidgetTester tester) async {
......
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