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Commit 8e4ca4bd authored by Adam Barth's avatar Adam Barth Committed by GitHub
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Draggable should have an affinity that selects an axis (#5985) 

This structure for the API is hopefully less confusing that the previous one
(which implied that vertical drags would not trigger horizontally draggable
widgets).

Fixes #1987
parent a95c9fdb
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Showing with 68 additions and 119 deletions
packages/flutter/lib/src/widgets/drag_target.dart
View file @ 8e4ca4bd
......@@ -49,13 +49,23 @@ enum DragAnchor {
pointer,
}
/// Subclass this widget to customize the gesture used to start a drag.
abstract class DraggableBase<T> extends StatefulWidget {
/// Initializes fields for subclasses.
/// A widget that can be dragged from to a [DragTarget].
///
/// When a draggable widget recognizes the start of a drag gesture, it displays
/// a [feedback] widget that tracks the user's finger across the screen. If the
/// user lifts their finger while on top of a [DragTarget], that target is given
/// the opportunity to accept the [data] carried by the draggble.
///
/// See also:
///
/// * [DragTarget]
/// * [LongPressDraggable]
class Draggable<T> extends StatefulWidget {
/// Creates a widget that can be dragged to a [DragTarget].
///
/// The [child] and [feedback] arguments must not be null. If
/// [maxSimultaneousDrags] is non-null, it must be positive.
DraggableBase({
Draggable({
Key key,
@required this.child,
@required this.feedback,
......@@ -63,6 +73,7 @@ abstract class DraggableBase<T> extends StatefulWidget {
this.childWhenDragging,
this.feedbackOffset: Offset.zero,
this.dragAnchor: DragAnchor.child,
this.affinity,
this.maxSimultaneousDrags,
this.onDraggableCanceled
}) : super(key: key) {
......@@ -95,6 +106,22 @@ abstract class DraggableBase<T> extends StatefulWidget {
/// Where this widget should be anchored during a drag.
final DragAnchor dragAnchor;
/// Controls how this widget competes with other gestures to initiate a drag.
///
/// If affinity is null, this widget initiates a drag as soon as it recognizes
/// a tap down gesture, regardless of any directionality. If affinity is
/// horizontal (or vertical), then this widget will compete with other
/// horizontal (or vertical, respectively) gestures.
///
/// For example, if this widget is placed in a vertically scrolling region and
/// has horizontal affinity, pointer motion in the vertical direction will
/// result in a scroll and pointer motion in the horizontal direction will
/// result in a drag. Conversely, if the widget has a null or vertical
/// affinity, pointer motion in any direction will result in a drag rather
/// than in a scroll because the draggable widget, being the more specific
/// widget, will out-compete the [Scrollable] for vertical gestures.
final Axis affinity;
/// How many simultaneous drags to support. When null, no limit is applied.
/// Set this to 1 if you want to only allow the drag source to have one item
/// dragged at a time.
......@@ -103,120 +130,27 @@ abstract class DraggableBase<T> extends StatefulWidget {
/// Called when the draggable is dropped without being accepted by a [DragTarget].
final DraggableCanceledCallback onDraggableCanceled;
/// Should return a new MultiDragGestureRecognizer instance
/// constructed with the given arguments.
MultiDragGestureRecognizer<MultiDragPointerState> createRecognizer(GestureMultiDragStartCallback onStart);
@override
_DraggableState<T> createState() => new _DraggableState<T>();
}
/// Makes its child draggable starting from tap down.
class Draggable<T> extends DraggableBase<T> {
/// Creates a widget that can be dragged starting from tap down.
/// Creates a gesture recognizer that recognizes the start of the drag.
///
/// The [child] and [feedback] arguments must not be null. If
/// [maxSimultaneousDrags] is non-null, it must be positive.
Draggable({
Key key,
@required Widget child,
@required Widget feedback,
T data,
Widget childWhenDragging,
Offset feedbackOffset: Offset.zero,
DragAnchor dragAnchor: DragAnchor.child,
int maxSimultaneousDrags,
DraggableCanceledCallback onDraggableCanceled
}) : super(
key: key,
child: child,
feedback: feedback,
data: data,
childWhenDragging: childWhenDragging,
feedbackOffset: feedbackOffset,
dragAnchor: dragAnchor,
maxSimultaneousDrags: maxSimultaneousDrags,
onDraggableCanceled: onDraggableCanceled
);
@override
ImmediateMultiDragGestureRecognizer createRecognizer(GestureMultiDragStartCallback onStart) {
/// Subclasses can override this function to customize when they start
/// recognizing a drag.
@protected
MultiDragGestureRecognizer<MultiDragPointerState> createRecognizer(GestureMultiDragStartCallback onStart) {
switch (affinity) {
case Axis.horizontal:
return new HorizontalMultiDragGestureRecognizer()..onStart = onStart;
case Axis.vertical:
return new VerticalMultiDragGestureRecognizer()..onStart = onStart;
}
return new ImmediateMultiDragGestureRecognizer()..onStart = onStart;
}
}
/// Makes its child draggable. When competing with other gestures,
/// this will only start the drag horizontally.
class HorizontalDraggable<T> extends DraggableBase<T> {
/// Creates a widget that can be dragged.
///
/// The [child] and [feedback] arguments must not be null. If
/// [maxSimultaneousDrags] is non-null, it must be positive.
HorizontalDraggable({
Key key,
@required Widget child,
@required Widget feedback,
T data,
Widget childWhenDragging,
Offset feedbackOffset: Offset.zero,
DragAnchor dragAnchor: DragAnchor.child,
int maxSimultaneousDrags,
DraggableCanceledCallback onDraggableCanceled
}) : super(
key: key,
child: child,
feedback: feedback,
data: data,
childWhenDragging: childWhenDragging,
feedbackOffset: feedbackOffset,
dragAnchor: dragAnchor,
maxSimultaneousDrags: maxSimultaneousDrags,
onDraggableCanceled: onDraggableCanceled
);
@override
HorizontalMultiDragGestureRecognizer createRecognizer(GestureMultiDragStartCallback onStart) {
return new HorizontalMultiDragGestureRecognizer()..onStart = onStart;
}
}
/// Makes its child draggable. When competing with other gestures,
/// this will only start the drag vertically.
class VerticalDraggable<T> extends DraggableBase<T> {
/// Creates a widget that can be dragged.
///
/// The [child] and [feedback] arguments must not be null. If
/// [maxSimultaneousDrags] is non-null, it must be positive.
VerticalDraggable({
Key key,
@required Widget child,
@required Widget feedback,
T data,
Widget childWhenDragging,
Offset feedbackOffset: Offset.zero,
DragAnchor dragAnchor: DragAnchor.child,
int maxSimultaneousDrags,
DraggableCanceledCallback onDraggableCanceled
}) : super(
key: key,
child: child,
feedback: feedback,
data: data,
childWhenDragging: childWhenDragging,
feedbackOffset: feedbackOffset,
dragAnchor: dragAnchor,
maxSimultaneousDrags: maxSimultaneousDrags,
onDraggableCanceled: onDraggableCanceled
);
@override
VerticalMultiDragGestureRecognizer createRecognizer(GestureMultiDragStartCallback onStart) {
return new VerticalMultiDragGestureRecognizer()..onStart = onStart;
}
_DraggableState<T> createState() => new _DraggableState<T>();
}
/// Makes its child draggable starting from long press.
class LongPressDraggable<T> extends DraggableBase<T> {
class LongPressDraggable<T> extends Draggable<T> {
/// Creates a widget that can be dragged starting from long press.
///
/// The [child] and [feedback] arguments must not be null. If
......@@ -255,7 +189,7 @@ class LongPressDraggable<T> extends DraggableBase<T> {
}
}
class _DraggableState<T> extends State<DraggableBase<T>> {
class _DraggableState<T> extends State<Draggable<T>> {
@override
void initState() {
super.initState();
......@@ -324,6 +258,17 @@ class _DraggableState<T> extends State<DraggableBase<T>> {
}
/// A widget that receives data when a [Draggable] widget is dropped.
///
/// When a draggable is dragged on top of a drag target, the drag target is
/// asked whether it will accept the data the draggable is carrying. If the user
/// does drop the draggable on top of the drag target (and the drag target has
/// indicated that it will accept the draggable's data), then the drag target is
/// asked to accept the draggable's data.
///
/// See also:
///
/// * [Draggable]
/// * [LongPressDraggable]
class DragTarget<T> extends StatefulWidget {
/// Creates a widget that receives drags.
///
......
packages/flutter/test/widget/draggable_test.dart
View file @ 8e4ca4bd
......@@ -315,15 +315,17 @@ void main() {
}
),
new Container(height: 400.0),
new HorizontalDraggable<int>(
new Draggable<int>(
data: 1,
child: new Text('H'),
feedback: new Text('Dragging')
feedback: new Text('Dragging'),
affinity: Axis.horizontal,
),
new VerticalDraggable<int>(
new Draggable<int>(
data: 2,
child: new Text('V'),
feedback: new Text('Dragging')
feedback: new Text('Dragging'),
affinity: Axis.vertical,
),
new Container(height: 500.0),
new Container(height: 500.0),
......@@ -420,15 +422,17 @@ void main() {
}
),
new Container(width: 400.0),
new HorizontalDraggable<int>(
new Draggable<int>(
data: 1,
child: new Text('H'),
feedback: new Text('Dragging')
feedback: new Text('Dragging'),
affinity: Axis.horizontal,
),
new VerticalDraggable<int>(
new Draggable<int>(
data: 2,
child: new Text('V'),
feedback: new Text('Dragging')
feedback: new Text('Dragging'),
affinity: Axis.vertical,
),
new Container(width: 500.0),
new Container(width: 500.0),
......
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