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Merge pull request #2453 from Hixie/placeholder-assert

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Clarify the assert when mimicking twice in a row.
This commit is contained in:
Ian Hickson 2016-03-06 11:24:57 -08:00
commit fdb4bd5e3d
1 changed files with 12 additions and 1 deletions
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13
packages/flutter/lib/src/widgets/mimic.dart
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@ -176,7 +176,18 @@ class MimicableState extends State<Mimicable> {
/// passing it to a [Mimic] widget. To mimic the child in the
/// [Overlay], consider using [liftToOverlay()] instead.
MimicableHandle startMimic() {
assert(_placeholderSize == null);
assert(() {
if (_placeholderSize != null) {
throw new WidgetError(
'Mimicable started while already active.\n'
'When startMimic() or liftToOverlay() is called on a MimicableState, the mimic becomes active. '
'While active, it cannot be reactivated until it is stopped. '
'To stop a Mimicable started with startMimic(), call the MimicableHandle object\'s stopMimic() method. '
'To stop a Mimicable started with liftToOverlay(), call dispose() on the MimicOverlayEntry.'
);
}
return true;
});
RenderBox box = context.findRenderObject();
assert(box != null);
assert(box.hasSize);