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// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/scheduler.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';
void main() {
testWidgets('Does not animate if already at target position', (WidgetTester tester) async {
final ScrollController controller = ScrollController();
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: ListView(
controller: controller,
children: List<Widget>.generate(80, (int i) => Text('$i', textDirection: TextDirection.ltr)),
),
),
);
expectNoAnimation();
final double currentPosition = controller.position.pixels;
controller.position.animateTo(currentPosition, duration: const Duration(seconds: 10), curve: Curves.linear);
expectNoAnimation();
expect(controller.position.pixels, currentPosition);
});
testWidgets('Does not animate if already at target position within tolerance', (WidgetTester tester) async {
final ScrollController controller = ScrollController();
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: ListView(
controller: controller,
children: List<Widget>.generate(80, (int i) => Text('$i', textDirection: TextDirection.ltr)),
),
),
);
expectNoAnimation();
final double halfTolerance = controller.position.physics.tolerance.distance / 2;
expect(halfTolerance, isNonZero);
final double targetPosition = controller.position.pixels + halfTolerance;
controller.position.animateTo(targetPosition, duration: const Duration(seconds: 10), curve: Curves.linear);
expectNoAnimation();
expect(controller.position.pixels, targetPosition);
});
testWidgets('Animates if going to a position outside of tolerance', (WidgetTester tester) async {
final ScrollController controller = ScrollController();
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: ListView(
controller: controller,
children: List<Widget>.generate(80, (int i) => Text('$i', textDirection: TextDirection.ltr)),
),
),
);
expectNoAnimation();
final double doubleTolerance = controller.position.physics.tolerance.distance * 2;
expect(doubleTolerance, isNonZero);
final double targetPosition = controller.position.pixels + doubleTolerance;
controller.position.animateTo(targetPosition, duration: const Duration(seconds: 10), curve: Curves.linear);
expect(SchedulerBinding.instance.transientCallbackCount, equals(1), reason: 'Expected an animation.');
});
}
void expectNoAnimation() {
expect(SchedulerBinding.instance.transientCallbackCount, equals(0), reason: 'Expected no animation.');
}