// Copyright 2017 The Chromium 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_test/flutter_test.dart'; import 'package:flutter/scheduler.dart'; import 'package:flutter/widgets.dart'; void main() { testWidgets('Does not animate if already at target position', (WidgetTester tester) async { final List<Widget> textWidgets = <Widget>[]; for (int i = 0; i < 80; i++) textWidgets.add(new Text('$i', textDirection: TextDirection.ltr)); final ScrollController controller = new ScrollController(); await tester.pumpWidget( new Directionality( textDirection: TextDirection.ltr, child: new ListView( children: textWidgets, controller: controller, ), ), ); expectNoAnimation(); final double currentPosition = controller.position.pixels; controller.position.animateTo(currentPosition, duration: const Duration(seconds: 10), curve: Curves.linear); expectNoAnimation(); expect(controller.position.pixels, currentPosition); }); testWidgets('Does not animate if already at target position within tolerance', (WidgetTester tester) async { final List<Widget> textWidgets = <Widget>[]; for (int i = 0; i < 80; i++) textWidgets.add(new Text('$i', textDirection: TextDirection.ltr)); final ScrollController controller = new ScrollController(); await tester.pumpWidget( new Directionality( textDirection: TextDirection.ltr, child: new ListView( children: textWidgets, controller: controller, ), ), ); 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 List<Widget> textWidgets = <Widget>[]; for (int i = 0; i < 80; i++) textWidgets.add(new Text('$i', textDirection: TextDirection.ltr)); final ScrollController controller = new ScrollController(); await tester.pumpWidget( new Directionality( textDirection: TextDirection.ltr, child: new ListView( children: textWidgets, controller: controller, ), ), ); 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.'); }