backup. before shop update

2021-08-31 13:28:33 -04:00
parent c378a6203c
commit 808ffa3211
292 changed files with 51551 additions and 695 deletions
--- a/lib/utils/shop_scroll_position.dart
+++ b/lib/utils/shop_scroll_position.dart
@@ -0,0 +1,292 @@
+import 'dart:math' as math;
+
+import 'package:flutter/gestures.dart';
+import 'package:flutter/physics.dart';
+import 'package:flutter/rendering.dart';
+import 'package:flutter/widgets.dart';
+
+import 'shop_scroll_coordinator.dart';
+
+/// 滑动位置信息
+class ShopScrollPosition extends ScrollPosition
+    implements ScrollActivityDelegate {
+  final ShopScrollCoordinator coordinator; // 协调器
+  ScrollDragController _currentDrag;
+  double _heldPreviousVelocity = 0.0;
+
+  ShopScrollPosition(
+      {@required ScrollPhysics physics,
+      @required ScrollContext context,
+      double initialPixels = 0.0,
+      bool keepScrollOffset = true,
+      ScrollPosition oldPosition,
+      String debugLabel,
+      @required this.coordinator})
+      : super(
+          physics: physics,
+          context: context,
+          keepScrollOffset: keepScrollOffset,
+          oldPosition: oldPosition,
+          debugLabel: debugLabel,
+        ) {
+    // 如果oldPosition不为null，则父级将首先调用Absorb()，它可以设置_pixels和_activity.
+    if (!hasPixels && initialPixels != null) correctPixels(initialPixels);
+    if (activity == null) goIdle();
+    assert(activity != null);
+  }
+
+  @override
+  AxisDirection get axisDirection => context.axisDirection;
+
+  @override
+  double setPixels(double newPixels) {
+    assert(activity.isScrolling);
+    return super.setPixels(newPixels);
+  }
+
+  @override
+  void absorb(ScrollPosition other) {
+    super.absorb(other);
+    if (other is! ScrollPositionWithSingleContext) {
+      goIdle();
+      return;
+    }
+    activity.updateDelegate(this);
+    final ShopScrollPosition typedOther = other as ShopScrollPosition;
+    _userScrollDirection = typedOther._userScrollDirection;
+    assert(_currentDrag == null);
+    if (typedOther._currentDrag != null) {
+      _currentDrag = typedOther._currentDrag;
+      _currentDrag.updateDelegate(this);
+      typedOther._currentDrag = null;
+    }
+  }
+
+  @override
+  void applyNewDimensions() {
+    super.applyNewDimensions();
+    context.setCanDrag(physics.shouldAcceptUserOffset(this));
+  }
+
+  /// 返回未使用的增量。
+  /// 正增量表示下降（在上方显示内容），负增量向上（在下方显示内容）。
+  double applyClampedDragUpdate(double delta) {
+    assert(delta != 0.0);
+    // 如果我们要朝向maxScrollExtent（负滚动偏移），那么我们在minScrollExtent方向上
+    // 可以达到的最大距离是负无穷大。 例如，如果我们已经过度滚动，则滚动以减少过度滚动不应禁止过度滚动。
+    // 如果我们要朝minScrollExtent（正滚动偏移量）方向移动，那么我们在minScrollExtent方向
+    // 上可以达到的最大距离是我们现在所处的位置（如果我们已经过度滚动）
+    // （在这种情况下，像素小于minScrollExtent），或者如果minScrollExtent可以 我们不是。
+    // 换句话说，我们不能通过applyClampedDragUpdate进入过滚动状态。
+    // 尽管如此，可能通过多种方式进入了过度滚动的情况。 一种是物理是否允许通过
+    // applyFullDragUpdate（请参见下文）。也可能会发生过度滚动的情况，例如 如果使用滚动控制器人工设置了滚动位置。
+    final double min =
+        delta < 0.0 ? -double.infinity : math.min(minScrollExtent, pixels);
+    // max的逻辑是等效的，但反向。
+    final double max =
+        delta > 0.0 ? double.infinity : math.max(maxScrollExtent, pixels);
+    final double oldPixels = pixels;
+    final double newPixels = (pixels - delta).clamp(min, max) as double;
+    final double clampedDelta = newPixels - pixels;
+    if (clampedDelta == 0.0) return delta;
+    final double overScroll = physics.applyBoundaryConditions(this, newPixels);
+    final double actualNewPixels = newPixels - overScroll;
+    final double offset = actualNewPixels - oldPixels;
+    if (offset != 0.0) {
+      forcePixels(actualNewPixels);
+      didUpdateScrollPositionBy(offset);
+    }
+    return delta + offset;
+  }
+
+  // Returns the overScroll. 返回过度滚动。
+  double applyFullDragUpdate(double delta) {
+    assert(delta != 0.0);
+    final double oldPixels = pixels;
+    // Apply friction: 施加摩擦：
+    final double newPixels =
+        pixels - physics.applyPhysicsToUserOffset(this, delta);
+    if (oldPixels == newPixels) return 0.0; // 增量一定很小，我们在添加浮点数时将其删除了
+    // Check for overScroll: 检查过度滚动：
+    final double overScroll = physics.applyBoundaryConditions(this, newPixels);
+    final double actualNewPixels = newPixels - overScroll;
+    if (actualNewPixels != oldPixels) {
+      forcePixels(actualNewPixels);
+      didUpdateScrollPositionBy(actualNewPixels - oldPixels);
+    }
+    return overScroll;
+  }
+
+  /// 当手指滑动时，该方法会获取到滑动距离
+  /// [delta]滑动距离，正增量表示下滑，负增量向上滑
+  /// 我们需要把子部件的 滑动数据 交给协调器处理，主部件无干扰
+  @override
+  void applyUserOffset(double delta) {
+    ScrollDirection userScrollDirection =
+        delta > 0.0 ? ScrollDirection.forward : ScrollDirection.reverse;
+    if (debugLabel != coordinator.pageLabel)
+      return coordinator.applyUserOffset(delta, userScrollDirection, this);
+    updateUserScrollDirection(userScrollDirection);
+    setPixels(pixels - physics.applyPhysicsToUserOffset(this, delta));
+  }
+
+  @override
+  void beginActivity(ScrollActivity newActivity) {
+    _heldPreviousVelocity = 0.0;
+    if (newActivity == null) return;
+    assert(newActivity.delegate == this);
+    super.beginActivity(newActivity);
+    _currentDrag?.dispose();
+    _currentDrag = null;
+    if (!activity.isScrolling) updateUserScrollDirection(ScrollDirection.idle);
+  }
+
+  /// 将[用户滚动方向]设置为给定值。
+  /// 如果更改了该值，则将分派[User ScrollNotification]。
+  @protected
+  @visibleForTesting
+  void updateUserScrollDirection(ScrollDirection value) {
+    assert(value != null);
+    if (userScrollDirection == value) return;
+    _userScrollDirection = value;
+    didUpdateScrollDirection(value);
+  }
+
+  @override
+  ScrollHoldController hold(VoidCallback holdCancelCallback) {
+    final double previousVelocity = activity.velocity;
+    final HoldScrollActivity holdActivity =
+        HoldScrollActivity(delegate: this, onHoldCanceled: holdCancelCallback);
+    beginActivity(holdActivity);
+    _heldPreviousVelocity = previousVelocity;
+    return holdActivity;
+  }
+
+  @override
+  Drag drag(DragStartDetails details, VoidCallback dragCancelCallback) {
+    final ScrollDragController drag = ScrollDragController(
+      delegate: this,
+      details: details,
+      onDragCanceled: dragCancelCallback,
+      carriedVelocity: physics.carriedMomentum(_heldPreviousVelocity),
+      motionStartDistanceThreshold: physics.dragStartDistanceMotionThreshold,
+    );
+    beginActivity(DragScrollActivity(this, drag));
+    assert(_currentDrag == null);
+    _currentDrag = drag;
+    return drag;
+  }
+
+  @override
+  void goIdle() {
+    beginActivity(IdleScrollActivity(this));
+  }
+
+  /// 以特定的速度开始一个物理驱动的模拟，该模拟确定[pixels]位置。
+  /// 此方法遵从[ScrollPhysics.createBallisticSimulation]，该方法通常在当前位置超出
+  /// 范围时提供滑动模拟，而在当前位置超出范围但具有非零速度时提供摩擦模拟。
+  /// 速度应以每秒逻辑像素为单位。
+  @override
+  void goBallistic(double velocity, [bool fromCoordinator = false]) {
+    if (debugLabel != coordinator.pageLabel) {
+      if (velocity > 0.0) coordinator.goBallistic(velocity);
+    } else {
+      if (fromCoordinator && velocity <= 0.0) return;
+      if (coordinator.pageExpand == PageExpandState.Expanding) return;
+    }
+    assert(pixels != null);
+    final Simulation simulation =
+        physics.createBallisticSimulation(this, velocity);
+    if (simulation != null) {
+      beginActivity(BallisticScrollActivity(this, simulation, context.vsync));
+    } else {
+      goIdle();
+    }
+  }
+
+  @override
+  bool applyContentDimensions(double minScrollExtent, double maxScrollExtent,
+      [bool fromCoordinator = false]) {
+    if (debugLabel == coordinator.pageLabel && !fromCoordinator)
+      return coordinator.applyContentDimensions(
+          minScrollExtent, maxScrollExtent, this);
+    return super.applyContentDimensions(minScrollExtent, maxScrollExtent);
+  }
+
+  @override
+  ScrollDirection get userScrollDirection => _userScrollDirection;
+  ScrollDirection _userScrollDirection = ScrollDirection.idle;
+
+  @override
+  Future<void> animateTo(
+    double to, {
+    @required Duration duration,
+    @required Curve curve,
+  }) {
+    if (nearEqual(to, pixels, physics.tolerance.distance)) {
+      // 跳过动画，直接移到我们已经靠近的位置。
+      jumpTo(to);
+      return Future<void>.value();
+    }
+
+    final DrivenScrollActivity activity = DrivenScrollActivity(
+      this,
+      from: pixels,
+      to: to,
+      duration: duration,
+      curve: curve,
+      vsync: context.vsync,
+    );
+    beginActivity(activity);
+    return activity.done;
+  }
+
+  @override
+  void jumpTo(double value) {
+    goIdle();
+    if (pixels != value) {
+      final double oldPixels = pixels;
+      forcePixels(value);
+      notifyListeners();
+      didStartScroll();
+      didUpdateScrollPositionBy(pixels - oldPixels);
+      didEndScroll();
+    }
+    goBallistic(0.0);
+  }
+
+  @Deprecated('This will lead to bugs.')
+  @override
+  void jumpToWithoutSettling(double value) {
+    goIdle();
+    if (pixels != value) {
+      final double oldPixels = pixels;
+      forcePixels(value);
+      notifyListeners();
+      didStartScroll();
+      didUpdateScrollPositionBy(pixels - oldPixels);
+      didEndScroll();
+    }
+  }
+
+  @override
+  void dispose() {
+    _currentDrag?.dispose();
+    _currentDrag = null;
+    super.dispose();
+  }
+
+  @override
+  void debugFillDescription(List<String> description) {
+    super.debugFillDescription(description);
+    description.add('${context.runtimeType}');
+    description.add('$physics');
+    description.add('$activity');
+    description.add('$userScrollDirection');
+  }
+
+  @override
+  void pointerScroll(double delta) {
+    // TODO: implement pointerScroll
+  }
+}