packages/flutter/test/widgets/list_view_builder_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/widgets.dart';
import 'package:flutter_test/flutter_test.dart';

import 'test_widgets.dart';

void main() {
  testWidgets('ListView.builder mount/dismount smoke test', (WidgetTester tester) async {
    final List<int> callbackTracker = <int>[];

    // the root view is 800x600 in the test environment
    // so if our widget is 100 pixels tall, it should fit exactly 6 times.

    Widget builder() {
      return Directionality(
        textDirection: TextDirection.ltr,
        child: FlipWidget(
          left: ListView.builder(
            itemExtent: 100.0,
            itemBuilder: (BuildContext context, int index) {
              callbackTracker.add(index);
              return SizedBox(
                key: ValueKey<int>(index),
                height: 100.0,
                child: Text('$index'),
              );
            },
          ),
          right: const Text('Not Today'),
        ),
      );
    }

    await tester.pumpWidget(builder());

    final FlipWidgetState testWidget = tester.state(find.byType(FlipWidget));

    expect(callbackTracker, equals(<int>[
      0, 1, 2, 3, 4, 5, // visible in viewport
      6, 7, 8, // in caching area
    ]));
    check(visible: <int>[0, 1, 2, 3, 4, 5], hidden: <int>[ 6, 7, 8]);

    callbackTracker.clear();
    testWidget.flip();
    await tester.pump();

    expect(callbackTracker, equals(<int>[]));

    callbackTracker.clear();
    testWidget.flip();
    await tester.pump();

    expect(callbackTracker, equals(<int>[
      0, 1, 2, 3, 4, 5,
      6, 7, 8, // in caching area
    ]));
    check(visible: <int>[0, 1, 2, 3, 4, 5], hidden: <int>[ 6, 7, 8]);
  });

  testWidgets('ListView.builder vertical', (WidgetTester tester) async {
    final List<int> callbackTracker = <int>[];

    // the root view is 800x600 in the test environment
    // so if our widget is 200 pixels tall, it should fit exactly 3 times.
    // but if we are offset by 300 pixels, there will be 4, numbered 1-4.

    Widget itemBuilder(BuildContext context, int index) {
      callbackTracker.add(index);
      return SizedBox(
        key: ValueKey<int>(index),
        width: 500.0, // this should be ignored
        height: 400.0, // should be overridden by itemExtent
        child: Text('$index', textDirection: TextDirection.ltr),
      );
    }

    Widget buildWidget() {
      return Directionality(
        textDirection: TextDirection.ltr,
        child: FlipWidget(
          left: ListView.builder(
            controller: ScrollController(initialScrollOffset: 300.0),
            itemExtent: 200.0,
            itemBuilder: itemBuilder,
          ),
          right: const Text('Not Today'),
        ),
      );
    }

    void jumpTo(double newScrollOffset) {
      final ScrollableState scrollable = tester.state(find.byType(Scrollable));
      scrollable.position.jumpTo(newScrollOffset);
    }

    await tester.pumpWidget(buildWidget());

    expect(callbackTracker, equals(<int>[
      0, // in caching area
      1, 2, 3, 4,
      5, // in caching area
    ]));
    check(visible: <int>[1, 2, 3, 4], hidden: <int>[0, 5]);
    callbackTracker.clear();

    jumpTo(400.0);
    // now only 3 should fit, numbered 2-4.

    await tester.pumpWidget(buildWidget());

    expect(callbackTracker, equals(<int>[
      0, 1, // in caching area
      2, 3, 4,
      5, 6, // in caching area
    ]));
    check(visible: <int>[2, 3, 4], hidden: <int>[0, 1, 5, 6]);
    callbackTracker.clear();

    jumpTo(500.0);
    // now 4 should fit, numbered 2-5.

    await tester.pumpWidget(buildWidget());

    expect(callbackTracker, equals(<int>[
      0, 1, // in caching area
      2, 3, 4, 5,
      6, // in caching area
    ]));
    check(visible: <int>[2, 3, 4, 5], hidden: <int>[0, 1, 6]);
    callbackTracker.clear();
  });

  testWidgets('ListView.builder horizontal', (WidgetTester tester) async {
    final List<int> callbackTracker = <int>[];

    // the root view is 800x600 in the test environment
    // so if our widget is 200 pixels wide, it should fit exactly 4 times.
    // but if we are offset by 300 pixels, there will be 5, numbered 1-5.

    Widget itemBuilder(BuildContext context, int index) {
      callbackTracker.add(index);
      return SizedBox(
        key: ValueKey<int>(index),
        width: 400.0, // this should be overridden by itemExtent
        height: 500.0, // this should be ignored
        child: Text('$index'),
      );
    }

    Widget buildWidget() {
      return Directionality(
        textDirection: TextDirection.ltr,
        child: FlipWidget(
          left: ListView.builder(
            controller: ScrollController(initialScrollOffset: 300.0),
            itemBuilder: itemBuilder,
            itemExtent: 200.0,
            scrollDirection: Axis.horizontal,
          ),
          right: const Text('Not Today'),
        ),
      );
    }

    void jumpTo(double newScrollOffset) {
      final ScrollableState scrollable = tester.state(find.byType(Scrollable));
      scrollable.position.jumpTo(newScrollOffset);
    }

    await tester.pumpWidget(buildWidget());

    expect(callbackTracker, equals(<int>[
      0, // in caching area
      1, 2, 3, 4, 5,
      6, // in caching area
    ]));
    check(visible: <int>[1, 2, 3, 4, 5], hidden: <int>[0, 6]);
    callbackTracker.clear();

    jumpTo(400.0);
    // now only 4 should fit, numbered 2-5.

    await tester.pumpWidget(buildWidget());

    expect(callbackTracker, equals(<int>[
      0, 1, // in caching area
      2, 3, 4, 5,
      6, 7, // in caching area
    ]));
    check(visible: <int>[2, 3, 4, 5], hidden: <int>[0, 1, 6, 7]);
    callbackTracker.clear();

    jumpTo(500.0);
    // now only 5 should fit, numbered 2-6.

    await tester.pumpWidget(buildWidget());

    expect(callbackTracker, equals(<int>[
      0, 1, // in caching area
      2, 3, 4, 5, 6,
      7, // in caching area
    ]));
    check(visible: <int>[2, 3, 4, 5, 6], hidden: <int>[0, 1, 7]);
    callbackTracker.clear();
  });

  testWidgets('ListView.builder 10 items, 2-3 items visible', (WidgetTester tester) async {
    final List<int> callbackTracker = <int>[];

    // The root view is 800x600 in the test environment and our list
    // items are 300 tall. Scrolling should cause two or three items
    // to be built.

    Widget itemBuilder(BuildContext context, int index) {
      callbackTracker.add(index);
      return Text('$index', key: ValueKey<int>(index), textDirection: TextDirection.ltr);
    }

    final Widget testWidget = Directionality(
      textDirection: TextDirection.ltr,
      child: ListView.builder(
        itemBuilder: itemBuilder,
        itemExtent: 300.0,
        itemCount: 10,
      ),
    );

    void jumpTo(double newScrollOffset) {
      final ScrollableState scrollable = tester.state(find.byType(Scrollable));
      scrollable.position.jumpTo(newScrollOffset);
    }

    await tester.pumpWidget(testWidget);
    expect(callbackTracker, equals(<int>[0, 1, 2]));
    check(visible: <int>[0, 1], hidden: <int>[2]);
    callbackTracker.clear();

    jumpTo(150.0);
    await tester.pump();

    expect(callbackTracker, equals(<int>[3]));
    check(visible: <int>[0, 1, 2], hidden: <int>[3]);
    callbackTracker.clear();

    jumpTo(600.0);
    await tester.pump();

    expect(callbackTracker, equals(<int>[4]));
    check(visible: <int>[2, 3], hidden: <int>[0, 1, 4]);
    callbackTracker.clear();

    jumpTo(750.0);
    await tester.pump();

    expect(callbackTracker, equals(<int>[5]));
    check(visible: <int>[2, 3, 4], hidden: <int>[0, 1, 5]);
    callbackTracker.clear();
  });

  testWidgets('ListView.builder 30 items with big jump, using prototypeItem', (WidgetTester tester) async {
    final List<int> callbackTracker = <int>[];

    // The root view is 800x600 in the test environment and our list
    // items are 300 tall. Scrolling should cause two or three items
    // to be built.

    Widget itemBuilder(BuildContext context, int index) {
      callbackTracker.add(index);
      return Text('$index', key: ValueKey<int>(index), textDirection: TextDirection.ltr);
    }

    final Widget testWidget = Directionality(
      textDirection: TextDirection.ltr,
      child: ListView.builder(
        itemBuilder: itemBuilder,
        prototypeItem: const SizedBox(
          width: 800,
          height: 300,
        ),
        itemCount: 30,
      ),
    );

    void jumpTo(double newScrollOffset) {
      final ScrollableState scrollable = tester.state(find.byType(Scrollable));
      scrollable.position.jumpTo(newScrollOffset);
    }

    await tester.pumpWidget(testWidget);

    // 2 is in the cache area, but not visible.
    expect(callbackTracker, equals(<int>[0, 1, 2]));
    final List<int> initialExpectedHidden = List<int>.generate(28, (int i) => i + 2);
    check(visible: <int>[0, 1], hidden: initialExpectedHidden);
    callbackTracker.clear();

    // Jump to the end of the ListView.
    jumpTo(8400);
    await tester.pump();

    // 27 is in the cache area, but not visible.
    expect(callbackTracker, equals(<int>[27, 28, 29]));
    final List<int> finalExpectedHidden = List<int>.generate(28, (int i) => i);
    check(visible: <int>[28, 29], hidden: finalExpectedHidden);
    callbackTracker.clear();
  });

  testWidgets('ListView.separated', (WidgetTester tester) async {
    Widget buildFrame({ required int itemCount }) {
      return Directionality(
        textDirection: TextDirection.ltr,
        child: ListView.separated(
          itemCount: itemCount,
          itemBuilder: (BuildContext context, int index) {
            return SizedBox(
              height: 100.0,
              child: Text('i$index'),
            );
          },
          separatorBuilder: (BuildContext context, int index) {
            return SizedBox(
              height: 10.0,
              child: Text('s$index'),
            );
          },
        ),
      );
    }

    await tester.pumpWidget(buildFrame(itemCount: 0));
    expect(find.text('i0'), findsNothing);
    expect(find.text('s0'), findsNothing);

    await tester.pumpWidget(buildFrame(itemCount: 1));
    expect(find.text('i0'), findsOneWidget);
    expect(find.text('s0'), findsNothing);

    await tester.pumpWidget(buildFrame(itemCount: 2));
    expect(find.text('i0'), findsOneWidget);
    expect(find.text('s0'), findsOneWidget);
    expect(find.text('i1'), findsOneWidget);
    expect(find.text('s1'), findsNothing);

    // ListView's height is 600, so items i0-i5 and s0-s4 fit.
    await tester.pumpWidget(buildFrame(itemCount: 25));
    for (final String s in <String>['i0', 's0', 'i1', 's1', 'i2', 's2', 'i3', 's3', 'i4', 's4', 'i5']) {
      expect(find.text(s), findsOneWidget);
    }
    expect(find.text('s5'), findsNothing);
    expect(find.text('i6'), findsNothing);
  });


  testWidgets('ListView.separated uses correct semanticChildCount', (WidgetTester tester) async {
    Widget buildFrame({ required int itemCount}) {
      return Directionality(
        textDirection: TextDirection.ltr,
        child: ListView.separated(
          itemCount: itemCount,
          itemBuilder: (BuildContext context, int index) {
            return SizedBox(
              height: 100.0,
              child: Text('i$index'),
            );
          },
          separatorBuilder: (BuildContext context, int index) {
            return SizedBox(
              height: 10.0,
              child: Text('s$index'),
            );
          },
        ),
      );
    }

    Scrollable scrollable() {
      return tester.widget<Scrollable>(
        find.descendant(
          of: find.byType(ListView),
          matching: find.byType(Scrollable),
        ),
      );
    }

    await tester.pumpWidget(buildFrame(itemCount: 0));
    expect(scrollable().semanticChildCount, 0);

    await tester.pumpWidget(buildFrame(itemCount: 1));
    expect(scrollable().semanticChildCount, 1);

    await tester.pumpWidget(buildFrame(itemCount: 2));
    expect(scrollable().semanticChildCount, 2);

    await tester.pumpWidget(buildFrame(itemCount: 3));
    expect(scrollable().semanticChildCount, 3);

    await tester.pumpWidget(buildFrame(itemCount: 4));
    expect(scrollable().semanticChildCount, 4);
  });

  // Regression test for https://github.com/flutter/flutter/issues/72292
  testWidgets('ListView.builder and SingleChildScrollView can work well together', (WidgetTester tester) async {
    Widget builder(int itemCount) {
      return Directionality(
        textDirection: TextDirection.ltr,
        child: SingleChildScrollView(
          child: ListView.builder(
            shrinkWrap: true,
            itemExtent: 35,
            itemCount: itemCount,
            itemBuilder: (BuildContext context, int index) {
              return const Text('I love Flutter.');
            },
          ),
        ),
      );
    }

    await tester.pumpWidget(builder(1));
    // Trigger relayout and garbage collect.
    await tester.pumpWidget(builder(2));
  });
}

void check({ List<int> visible = const <int>[], List<int> hidden = const <int>[] }) {
  for (final int i in visible) {
    expect(find.text('$i'), findsOneWidget);
  }
  for (final int i in hidden) {
    expect(find.text('$i'), findsNothing);
  }
}