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fix a dropdown button menu position bug (#89199)

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xubaolin 2021-09-11 11:17:04 +08:00 committed by GitHub
parent 3a6085474c
commit b2550fe5fa
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 39 additions and 5 deletions
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21
packages/flutter/lib/src/material/dropdown.dart
View File

@ -517,7 +517,10 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
// selected item is aligned with the button's vertical center, as far as
// that's possible given availableHeight.
_MenuLimits getMenuLimits(Rect buttonRect, double availableHeight, int index) {
final double maxMenuHeight = availableHeight - 2.0 * _kMenuItemHeight;
double computedMaxHeight = availableHeight - 2.0 * _kMenuItemHeight;
if (menuMaxHeight != null) {
computedMaxHeight = math.min(computedMaxHeight, menuMaxHeight!);
}
final double buttonTop = buttonRect.top;
final double buttonBottom = math.min(buttonRect.bottom, availableHeight);
final double selectedItemOffset = getItemOffset(index);
@ -535,8 +538,8 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
preferredMenuHeight += itemHeights.reduce((double total, double height) => total + height);
// If there are too many elements in the menu, we need to shrink it down
// so it is at most the maxMenuHeight.
final double menuHeight = math.min(maxMenuHeight, preferredMenuHeight);
// so it is at most the computedMaxHeight.
final double menuHeight = math.min(computedMaxHeight, preferredMenuHeight);
double menuBottom = menuTop + menuHeight;
// If the computed top or bottom of the menu are outside of the range
@ -544,14 +547,21 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
// than the button height and the button is at the very bottom or top of the
// screen, the menu will be aligned with the bottom or top of the button
// respectively.
if (menuTop < topLimit)
if (menuTop < topLimit) {
menuTop = math.min(buttonTop, topLimit);
menuBottom = menuTop + menuHeight;
}
if (menuBottom > bottomLimit) {
menuBottom = math.max(buttonBottom, bottomLimit);
menuTop = menuBottom - menuHeight;
}
if (menuBottom - itemHeights[selectedIndex] / 2.0 < buttonBottom - buttonRect.height / 2.0) {
menuBottom = buttonBottom - buttonRect.height / 2.0 + itemHeights[selectedIndex] / 2.0;
menuTop = menuBottom - menuHeight;
}
double scrollOffset = 0;
// If all of the menu items will not fit within availableHeight then
// compute the scroll offset that will line the selected menu item up
@ -559,7 +569,7 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
// shown - subsequently we leave the scroll offset where the user left
// it. This scroll offset is only accurate for fixed height menu items
// (the default).
if (preferredMenuHeight > maxMenuHeight) {
if (preferredMenuHeight > computedMaxHeight) {
// The offset should be zero if the selected item is in view at the beginning
// of the menu. Otherwise, the scroll offset should center the item if possible.
scrollOffset = math.max(0.0, selectedItemOffset - (buttonTop - menuTop));
@ -568,6 +578,7 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
scrollOffset = math.min(scrollOffset, preferredMenuHeight - menuHeight);
}
assert(menuHeight == menuBottom - menuTop);
return _MenuLimits(menuTop, menuBottom, menuHeight, scrollOffset);
}
}

23
packages/flutter/test/material/dropdown_test.dart
View File

@ -3127,6 +3127,29 @@ void main() {
expect(menuHeight, defaultMenuHeight);
});
// Regression test for https://github.com/flutter/flutter/issues/89029
testWidgets('menu position test with `menuMaxHeight`', (WidgetTester tester) async {
final Key buttonKey = UniqueKey();
await tester.pumpWidget(buildFrame(
buttonKey: buttonKey,
value: '6',
items: List<String>.generate(/*length=*/64, (int index) => index.toString()),
onChanged: onChanged,
menuMaxHeight: 2 * kMinInteractiveDimension,
));
await tester.tap(find.text('6'));
await tester.pumpAndSettle();
final RenderBox menuBox = tester.renderObject(find.byType(ListView));
final RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
// The menu's bottom should align with the drop-button's bottom.
expect(
menuBox.localToGlobal(menuBox.paintBounds.bottomCenter).dy,
buttonBox.localToGlobal(buttonBox.paintBounds.bottomCenter).dy,
);
});
// Regression test for https://github.com/flutter/flutter/issues/76614
testWidgets('Do not crash if used in very short screen', (WidgetTester tester) async {
// The default item height is 48.0 pixels and needs two items padding since