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Description:

collapsible

collapsible #
A widget that implicitly collapses and expands around its child by clipping it.
Usage #
import 'package:collapsible/collapsible.dart';
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[Collapsible] has three required parameters: [child], [collapsed], and [axis].
[child] provides the widget [Collapsible] wraps, while [collapsed] defines
the current state, whether its collapsed or not, and [axis] specifies whether
the collapsing/expanding animation should transition horizontally, vertically,
or along both axes.
/// When updated to `false` the [Collapsible] will expand, revealing its
/// child, and will collapse, hiding the child if set back to `true`.
var _collapsed = true;

/// A [Collapsible] built with its default parameters.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
child: MyWidget(),
);
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Alignment #
Depending on the [axis] of the transition and the [Collapsible]'s placement
within its parent, you'll likely want to change the [alignment] of the [child]
to match that of the [Collapsible]'s alignment within its parent.
/// When collapsing vertically and the [Collapsible] is aligned to
/// the top edge of its parent, the [child] will look best if aligned
/// to the top-center of the [Collapsible].
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.vertical,
alignment: Alignment.topCenter,
child: MyWidget(),
);
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Restricting the Size #
The minimum width and height the [Collapsible] will collapse to can be provided
as factors that the [child]'s size will be multiplied by.
Specifying a minimum width/height factor can be a good idea if you want to
clip only a part of the [child] or if you'd like the child to continue
occupying space within its parent when collapsed.
/// A [Collapsible] that collapses to 20% of the width and 40% of the
/// height of its child.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
minWidthFactor: 0.2,
minHeightFactor: 0.4,
child: MyWidget(),
);
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Fading #
[Collapsible] has a parameter, [fade], that if set to true, will wrap the
[child] with an [AnimatedOpacity] widget, which will fade the child in/out
as the [Collapsible] expands/collapses.
The minimum opacity the [child] should fade to can be specified with the
[minOpacity] parameter, which defaults to 0.0 (0%).
/// A [Collapsible] that fades its child in/out as it expands/collapses,
/// fading it out to 20% opacity.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.horizontal,
fade: true,
minOpacity: 0.2,
child: MyWidget(),
);
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Curve #
An easing curve can be applied to the animation with the [curve] parameter,
the curve will also be applied to the fading animation if [fade] is true.
[curve] defaults to Curves.easeOut.
/// A [Collapsible] whose animations start slowly then speed up.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
curve: Curves.easeIn,
fade: true,
child: MyWidget(),
);
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Duration #
The [duration] of the animation can also be provided, which defaults to 240ms.
/// A [Collapsible] that takes 1 second to expand/collapse around its child.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
duration: Duration(seconds: 1),
child: MyWidget(),
);
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Depending on the [curve] you may want to provide a different duration
for the collapsing and expanding animations for a smoother appearance.
/// A [Collapsible] that takes 240ms to collapse and 360ms to expand.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
duration: Duration(milliseconds: _collapsed ? 240 : 360),
child: MyWidget(),
);
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State Management #
MaintainState #
With the default settings, the [Collapsible] will replace the [child] with
a SizedBox.shrink() to free up the resources used by the [child]. This
means every time the [child] is revealed it will be built from a fresh state.
To prevent this, [maintainState] can be set to true, which will tell the
[Collapsible] to build the [child] once and keep it built.
/// A [Collapsible] that maintains the state of its child when the
/// child is hidden.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
maintainState: true,
child: MyWidget(),
);
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[maintainState] will automatically be set to true if the [child] still
occupies any space when the [Collapsible] is in its collapsed space. This
occurs when [minWidthFactor] or [minHeightFactor] are greater than 0.0
and the transition occurs along the horizontal or vertical axes respectively.
MaintainAnimation #
By default, the [Collapsible] will stop any of the childs', or its sub-trees',
animation tickers when in the collapsed state. [maintainAnimation] can be
set to true to keep them running.
/// A [Collapsible] that maintains the animations of its child when collapsed.
Collapsible(
collapsed: _collapsed,
axis: CollapsibleAxis.both,
maintainAnimation: true,
child: MyWidget(),
);
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Setting [maintainAnimation] to true will automatically set [maintainState]
to true, but unlike [maintainState], [maintainAnimation] will remain
false even if part of the child is still in view when collapsed, it must
be set to true to keep the tickers active.