Appbar slivers. (#7631)

packages/flutter/lib/rendering.dart

@@ -45,6 +45,7 @@ export 'src/rendering/rotated_box.dart';
 export 'src/rendering/semantics.dart';
 export 'src/rendering/shifted_box.dart';
 export 'src/rendering/sliver.dart';
+export 'src/rendering/sliver_app_bar.dart';
 export 'src/rendering/sliver_block.dart';
 export 'src/rendering/stack.dart';
 export 'src/rendering/table.dart';

packages/flutter/lib/src/widgets/app_bar.dart

+// Copyright 2015 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/foundation.dart';
+import 'package:flutter/rendering.dart';
+
+import 'framework.dart';
+
+abstract class SliverAppBarDelegate {
+  /// Abstract const constructor. This constructor enables subclasses to provide
+  /// const constructors so that they can be used in const expressions.
+  const SliverAppBarDelegate();
+
+  Widget build(BuildContext context, double shrinkOffset);
+
+  double get maxExtent;
+
+  bool shouldRebuild(@checked SliverAppBarDelegate oldDelegate);
+}
+
+class SliverAppBar extends StatelessWidget {
+  SliverAppBar({
+    Key key,
+    @required this.delegate,
+    this.pinned: false,
+    this.floating: false,
+  }) : super(key: key) {
+    assert(delegate != null);
+    assert(pinned != null);
+    assert(floating != null);
+    assert(!pinned || !floating);
+  }
+
+  final SliverAppBarDelegate delegate;
+
+  final bool pinned;
+
+  final bool floating;
+
+  @override
+  Widget build(BuildContext context) {
+    if (pinned)
+      return new _SliverPinnedAppBar(delegate: delegate);
+    if (floating)
+      return new _SliverFloatingAppBar(delegate: delegate);
+    return new _SliverScrollingAppBar(delegate: delegate);
+  }
+
+  @override
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    description.add('delegate: $delegate');
+    List<String> flags = <String>[];
+    if (pinned)
+      flags.add('pinned');
+    if (floating)
+      flags.add('floating');
+    if (flags.isEmpty)
+      flags.add('normal');
+    description.add('mode: ${flags.join(", ")}');
+  }
+}
+
+class _SliverAppBarElement extends RenderObjectElement {
+  _SliverAppBarElement(_SliverAppBarRenderObjectWidget widget) : super(widget);
+
+  @override
+  _SliverAppBarRenderObjectWidget get widget => super.widget;
+
+  @override
+  _RenderSliverAppBarForWidgetsMixin get renderObject => super.renderObject;
+
+  @override
+  void mount(Element parent, dynamic newSlot) {
+    super.mount(parent, newSlot);
+    renderObject._element = this;
+  }
+
+  @override
+  void unmount() {
+    super.unmount();
+    renderObject._element = null;
+  }
+
+  @override
+  void update(_SliverAppBarRenderObjectWidget newWidget) {
+    final _SliverAppBarRenderObjectWidget oldWidget = widget;
+    super.update(newWidget);
+    final SliverAppBarDelegate newDelegate = newWidget.delegate;
+    final SliverAppBarDelegate oldDelegate = oldWidget.delegate;
+    if (newDelegate != oldDelegate &&
+        (newDelegate.runtimeType != oldDelegate.runtimeType || newDelegate.shouldRebuild(oldDelegate)))
+      renderObject.triggerRebuild();
+  }
+
+  @override
+  void performRebuild() {
+    renderObject.triggerRebuild();
+  }
+
+  Element child;
+
+  void _build(double shrinkOffset) {
+    owner.buildScope(this, () {
+      child = updateChild(child, widget.delegate.build(this, shrinkOffset), null);
+    });
+  }
+
+  @override
+  void forgetChild(Element child) {
+    assert(child == this.child);
+    this.child = null;
+  }
+
+  @override
+  void insertChildRenderObject(@checked RenderObject child, Null slot) {
+    renderObject.child = child;
+  }
+
+  @override
+  void moveChildRenderObject(@checked RenderObject child, Null slot) {
+    assert(false);
+  }
+
+  @override
+  void removeChildRenderObject(@checked RenderObject child) {
+    renderObject.child = null;
+  }
+
+  @override
+  void visitChildren(ElementVisitor visitor) {
+    visitor(child);
+  }
+}
+
+abstract class _SliverAppBarRenderObjectWidget extends RenderObjectWidget {
+  _SliverAppBarRenderObjectWidget({
+    Key key,
+    @required this.delegate,
+  }) : super(key: key) {
+    assert(delegate != null);
+  }
+
+  final SliverAppBarDelegate delegate;
+
+  @override
+  _SliverAppBarElement createElement() => new _SliverAppBarElement(this);
+
+  @override
+  _RenderSliverAppBarForWidgetsMixin createRenderObject(BuildContext context);
+
+  @override
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    description.add('delegate: $delegate');
+  }
+}
+
+abstract class _RenderSliverAppBarForWidgetsMixin implements RenderSliverAppBar {
+  _SliverAppBarElement _element;
+
+  @override
+  double get maxExtent => _element.widget.delegate.maxExtent;
+
+  @override
+  void updateChild(double shrinkOffset) {
+    assert(_element != null);
+    _element._build(shrinkOffset);
+  }
+
+  @protected
+  void triggerRebuild() {
+    markNeedsUpdate();
+  }
+}
+
+class _SliverScrollingAppBar extends _SliverAppBarRenderObjectWidget {
+  _SliverScrollingAppBar({
+    Key key,
+    @required SliverAppBarDelegate delegate,
+  }) : super(key: key, delegate: delegate);
+
+  @override
+  _RenderSliverAppBarForWidgetsMixin createRenderObject(BuildContext context) {
+    return new _RenderSliverScrollingAppBarForWidgets();
+  }
+}
+
+// This class exists to work around https://github.com/dart-lang/sdk/issues/15101
+abstract class _RenderSliverScrollingAppBar extends RenderSliverScrollingAppBar { }
+
+class _RenderSliverScrollingAppBarForWidgets extends _RenderSliverScrollingAppBar
+  with _RenderSliverAppBarForWidgetsMixin { }
+
+class _SliverPinnedAppBar extends _SliverAppBarRenderObjectWidget {
+  _SliverPinnedAppBar({
+    Key key,
+    @required SliverAppBarDelegate delegate,
+  }) : super(key: key, delegate: delegate);
+
+  @override
+  _RenderSliverAppBarForWidgetsMixin createRenderObject(BuildContext context) {
+    return new _RenderSliverPinnedAppBarForWidgets();
+  }
+}
+
+// This class exists to work around https://github.com/dart-lang/sdk/issues/15101
+abstract class _RenderSliverPinnedAppBar extends RenderSliverPinnedAppBar { }
+
+class _RenderSliverPinnedAppBarForWidgets extends _RenderSliverPinnedAppBar with _RenderSliverAppBarForWidgetsMixin { }
+
+class _SliverFloatingAppBar extends _SliverAppBarRenderObjectWidget {
+  _SliverFloatingAppBar({
+    Key key,
+    @required SliverAppBarDelegate delegate,
+  }) : super(key: key, delegate: delegate);
+
+  @override
+  _RenderSliverAppBarForWidgetsMixin createRenderObject(BuildContext context) {
+    return new _RenderSliverFloatingAppBarForWidgets();
+  }
+}
+
+// This class exists to work around https://github.com/dart-lang/sdk/issues/15101
+abstract class _RenderSliverFloatingAppBar extends RenderSliverFloatingAppBar { }
+
+class _RenderSliverFloatingAppBarForWidgets extends _RenderSliverFloatingAppBar with _RenderSliverAppBarForWidgetsMixin { }

packages/flutter/lib/widgets.dart

@@ -10,6 +10,7 @@ library widgets;
 export 'src/widgets/animated_cross_fade.dart';
 export 'src/widgets/animated_size.dart';
 export 'src/widgets/app.dart';
+export 'src/widgets/app_bar.dart';
 export 'src/widgets/banner.dart';
 export 'src/widgets/basic.dart';
 export 'src/widgets/binding.dart';

packages/flutter/test/widgets/slivers_appbar_scrolling_test.dart

+// Copyright 2016 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/rendering.dart';
+import 'package:flutter/widgets.dart';
+
+void verifyPaintPosition(GlobalKey key, Offset ideal) {
+  RenderObject target = key.currentContext.findRenderObject();
+  expect(target.parent, new isInstanceOf<RenderViewport2>());
+  SliverPhysicalParentData parentData = target.parentData;
+  Offset actual = parentData.paintOffset;
+  expect(actual, ideal);
+}
+
+void main() {
+  testWidgets('Sliver appbars - scrolling', (WidgetTester tester) async {
+    final GlobalKey<Scrollable2State> scrollableKey = new GlobalKey<Scrollable2State>();
+    GlobalKey key1, key2, key3, key4, key5;
+    await tester.pumpWidget(
+      new Scrollable2(
+        key: scrollableKey,
+        axisDirection: AxisDirection.down,
+        children: <Widget>[
+          new BigSliver(key: key1 = new GlobalKey()),
+          new SliverAppBar(key: key2 = new GlobalKey(), delegate: new TestDelegate()),
+          new SliverAppBar(key: key3 = new GlobalKey(), delegate: new TestDelegate()),
+          new BigSliver(key: key4 = new GlobalKey()),
+          new BigSliver(key: key5 = new GlobalKey()),
+        ],
+      ),
+    );
+    AbsoluteScrollPosition position = scrollableKey.currentState.position;
+    final double max = RenderBigSliver.height * 3.0 + new TestDelegate().maxExtent * 2.0 - 600.0; // 600 is the height of the test viewport
+    assert(max < 10000.0);
+    expect(max, 1450.0);
+    expect(position.pixels, 0.0);
+    expect(position.minScrollExtent, 0.0);
+    expect(position.maxScrollExtent, max);
+    position.animate(to: 10000.0, curve: Curves.linear, duration: const Duration(minutes: 1));
+    await tester.pumpUntilNoTransientCallbacks(const Duration(milliseconds: 10));
+    expect(position.pixels, max);
+    expect(position.minScrollExtent, 0.0);
+    expect(position.maxScrollExtent, max);
+    verifyPaintPosition(key1, new Offset(0.0, 0.0));
+    verifyPaintPosition(key2, new Offset(0.0, 0.0));
+    verifyPaintPosition(key3, new Offset(0.0, 0.0));
+    verifyPaintPosition(key4, new Offset(0.0, 0.0));
+    verifyPaintPosition(key5, new Offset(0.0, 50.0));
+  });
+
+  testWidgets('Sliver appbars - scrolling off screen', (WidgetTester tester) async {
+    final GlobalKey<Scrollable2State> scrollableKey = new GlobalKey<Scrollable2State>();
+    GlobalKey key = new GlobalKey();
+    TestDelegate delegate = new TestDelegate();
+    await tester.pumpWidget(
+      new Scrollable2(
+        key: scrollableKey,
+        axisDirection: AxisDirection.down,
+        children: <Widget>[
+          new BigSliver(),
+          new SliverAppBar(key: key, delegate: delegate),
+          new BigSliver(),
+          new BigSliver(),
+        ],
+      ),
+    );
+    AbsoluteScrollPosition position = scrollableKey.currentState.position;
+    position.animate(to: RenderBigSliver.height + delegate.maxExtent - 5.0, curve: Curves.linear, duration: const Duration(minutes: 1));
+    await tester.pumpUntilNoTransientCallbacks(const Duration(milliseconds: 1000));
+    RenderBox box = tester.renderObject/*<RenderBox>*/(find.byType(Container));
+    Rect rect = new Rect.fromPoints(box.localToGlobal(Point.origin), box.localToGlobal(box.size.bottomRight(Point.origin)));
+    expect(rect, equals(new Rect.fromLTWH(0.0, -195.0, 800.0, 200.0)));
+  });
+}
+
+class TestDelegate extends SliverAppBarDelegate {
+  @override
+  double get maxExtent => 200.0;
+
+  @override
+  Widget build(BuildContext context, double shrinkOffset) {
+    return new Container(height: maxExtent);
+  }
+
+  @override
+  bool shouldRebuild(TestDelegate oldDelegate) => false;
+}
+
+
+class RenderBigSliver extends RenderSliver {
+  static const double height = 550.0;
+  double get paintExtent => (height - constraints.scrollOffset).clamp(0.0, constraints.remainingPaintExtent);
+
+  @override
+  void performLayout() {
+    geometry = new SliverGeometry(
+      scrollExtent: height,
+      paintExtent: paintExtent,
+      maxPaintExtent: height,
+    );
+  }
+}
+
+class BigSliver extends LeafRenderObjectWidget {
+  BigSliver({ Key key }) : super(key: key);
+  @override
+  RenderBigSliver createRenderObject(BuildContext context) {
+    return new RenderBigSliver();
+  }
+}