flutter_flutter/packages/flutter/test/widgets/slivers_appbar_stretch_test.dart

// 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/material.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group('SliverAppBar - Stretch', () {
    testWidgets('fills overscroll', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      final RenderSliverScrollingPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(200.0));
    });

    testWidgets('fills overscroll after reverse direction input - scrolling header', (
      WidgetTester tester,
    ) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(title: Text('Test'), stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      final RenderSliverScrollingPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      expect(tester.getCenter(find.text('Test')).dy, 28.0);
      // First scroll the header away
      final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byKey(anchor)));
      await gesture.moveBy(const Offset(0.0, -100.0));
      await tester.pump(const Duration(milliseconds: 10));
      expect(header.child!.size.height, equals(56.0));
      expect(tester.getCenter(find.text('Test', skipOffstage: false)).dy, -28.0);
      // With the same gesture, scroll back and into overscroll
      await gesture.moveBy(const Offset(0.0, 200.0));
      await tester.pump(const Duration(milliseconds: 10));
      // Header should stretch in overscroll
      expect(header.child!.size.height, equals(200.0));
      expect(tester.getCenter(find.text('Test')).dy, 28.0);
      await gesture.up();
      await tester.pumpAndSettle();
    });

    testWidgets('fills overscroll after reverse direction input - floating header', (
      WidgetTester tester,
    ) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(
                title: Text('Test'),
                stretch: true,
                floating: true,
                expandedHeight: 100.0,
              ),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      final RenderSliverFloatingPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      expect(tester.getCenter(find.text('Test')).dy, 28.0);
      // First scroll the header away
      final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byKey(anchor)));
      await gesture.moveBy(const Offset(0.0, -100.0));
      await tester.pump(const Duration(milliseconds: 10));
      expect(header.child!.size.height, equals(56.0));
      expect(tester.getCenter(find.text('Test', skipOffstage: false)).dy, -28.0);
      // With the same gesture, scroll back and into overscroll
      await gesture.moveBy(const Offset(0.0, 200.0));
      await tester.pump(const Duration(milliseconds: 10));
      // Header should stretch in overscroll
      expect(header.child!.size.height, equals(200.0));
      expect(tester.getCenter(find.text('Test')).dy, 28.0);
      await gesture.up();
      await tester.pumpAndSettle();
    });

    testWidgets('does not stretch without overscroll physics', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const ClampingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      final RenderSliverScrollingPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100.0));
      expect(header.child!.size.height, equals(100.0));
    });

    testWidgets('default trigger offset', (WidgetTester tester) async {
      var didTrigger = false;
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              SliverAppBar(
                stretch: true,
                expandedHeight: 100.0,
                onStretchTrigger: () async {
                  didTrigger = true;
                },
              ),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      await slowDrag(tester, anchor, const Offset(0.0, 50.0));
      expect(didTrigger, isFalse);
      await tester.pumpAndSettle();
      await slowDrag(tester, anchor, const Offset(0.0, 150.0));
      expect(didTrigger, isTrue);
    });

    testWidgets('custom trigger offset', (WidgetTester tester) async {
      var didTrigger = false;
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              SliverAppBar(
                stretch: true,
                expandedHeight: 100.0,
                stretchTriggerOffset: 150.0,
                onStretchTrigger: () async {
                  didTrigger = true;
                },
              ),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      await slowDrag(tester, anchor, const Offset(0.0, 100.0));
      await tester.pumpAndSettle();
      expect(didTrigger, isFalse);
      await slowDrag(tester, anchor, const Offset(0.0, 300.0));
      expect(didTrigger, isTrue);
    });

    testWidgets('stretch callback not triggered without overscroll physics', (
      WidgetTester tester,
    ) async {
      var didTrigger = false;
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const ClampingScrollPhysics(),
            slivers: <Widget>[
              SliverAppBar(
                stretch: true,
                expandedHeight: 100.0,
                stretchTriggerOffset: 150.0,
                onStretchTrigger: () async {
                  didTrigger = true;
                },
              ),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );

      await slowDrag(tester, anchor, const Offset(0.0, 100.0));
      await tester.pumpAndSettle();
      expect(didTrigger, isFalse);
      await slowDrag(tester, anchor, const Offset(0.0, 300.0));
      expect(didTrigger, isFalse);
    });

    testWidgets('asserts reasonable trigger offset', (WidgetTester tester) async {
      expect(() {
        return MaterialApp(
          home: CustomScrollView(
            physics: const ClampingScrollPhysics(),
            slivers: <Widget>[
              SliverAppBar(stretch: true, expandedHeight: 100.0, stretchTriggerOffset: -150.0),
              SliverToBoxAdapter(child: Container(height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        );
      }, throwsAssertionError);
    });
  });

  group('SliverAppBar - Stretch, Pinned', () {
    testWidgets('fills overscroll', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(pinned: true, stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );
      final RenderSliverPinnedPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(200.0));
    });

    testWidgets('does not stretch without overscroll physics', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const ClampingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(pinned: true, stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );
      final RenderSliverPinnedPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(100.0));
    });
  });

  group('SliverAppBar - Stretch, Floating', () {
    testWidgets('fills overscroll', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(floating: true, stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );
      final RenderSliverFloatingPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(200.0));
    });

    testWidgets('does not fill overscroll without proper physics', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const ClampingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(floating: true, stretch: true, expandedHeight: 100.0),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );
      final RenderSliverFloatingPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(100.0));
    });
  });

  group('SliverAppBar - Stretch, Floating, Pinned', () {
    testWidgets('fills overscroll', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const BouncingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(
                floating: true,
                pinned: true,
                stretch: true,
                expandedHeight: 100.0,
              ),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );
      final RenderSliverFloatingPinnedPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(200.0));
    });

    testWidgets('does not fill overscroll without proper physics', (WidgetTester tester) async {
      const anchor = Key('drag');
      await tester.pumpWidget(
        MaterialApp(
          home: CustomScrollView(
            physics: const ClampingScrollPhysics(),
            slivers: <Widget>[
              const SliverAppBar(
                pinned: true,
                floating: true,
                stretch: true,
                expandedHeight: 100.0,
              ),
              SliverToBoxAdapter(child: Container(key: anchor, height: 800)),
              SliverToBoxAdapter(child: Container(height: 800)),
            ],
          ),
        ),
      );
      final RenderSliverFloatingPinnedPersistentHeader header = tester.renderObject(
        find.byType(SliverAppBar),
      );
      expect(header.child!.size.height, equals(100.0));
      await slowDrag(tester, anchor, const Offset(0.0, 100));
      expect(header.child!.size.height, equals(100.0));
    });
  });
}

Future<void> slowDrag(WidgetTester tester, Key widget, Offset offset) async {
  final Offset target = tester.getCenter(find.byKey(widget));
  final TestGesture gesture = await tester.startGesture(target);
  await gesture.moveBy(offset);
  await tester.pump(const Duration(milliseconds: 10));
  await gesture.up();
}