ios - 使用 UIAttachmentBehavior 拖动 View

Question

我想拖动一个 UIView，并让它移动附加到它的其他 View 的位置，就好像它们都是通过字符串附加的一样。起始状态将是一堆 UIViews 聚集在一起。如果你拉出一个，一旦它与被拖动的 View 之间的最小距离达到最小距离，它所连接的项目就会开始移动。我当时认为实现此目的的最佳方法是使用 UIDynamicItemBehavior 考虑到我需要它回到原位并对其应用重量。我不太确定如何在不执行荒谬代码的情况下完成此操作。我的代码可以在下面看到。不幸的是，我遇到了正方形项目被拖回 square2 的问题。谁有任何建议，我很乐意澄清是否需要。

- (void)viewDidLoad
{
    [super viewDidLoad];

    _containmentView = [[UIView alloc] initWithFrame:CGRectMake(0.0, self.view.frame.size.height/2, self.view.frame.size.width, 200)];
    [self.view addSubview:_containmentView];
    [_containmentView setBackgroundColor:[UIColor greenColor]];

    _square = [[UIView alloc]initWithFrame:CGRectMake(200, 0, 100, 100)];
    _square.backgroundColor = [UIColor yellowColor];
    [_containmentView addSubview:_square];

    _square2 = [[UIView alloc]initWithFrame:CGRectMake(100, 0, 100, 100)];
    _square2.backgroundColor = [UIColor redColor];
    [_containmentView addSubview:_square2];


    _animator = [[UIDynamicAnimator alloc]initWithReferenceView:_containmentView];
    _gravity = [[UIGravityBehavior alloc]initWithItems:@[_square, _square2]];
    _gravity.gravityDirection = CGVectorMake(-1.0, 0.0);
    [_animator addBehavior:_gravity];

    _collision = [[UICollisionBehavior alloc]initWithItems:@[_square]];
    _collision.collisionDelegate = self;
    _collision.translatesReferenceBoundsIntoBoundary = YES; //causes the boundary to use the bounds of the reference view supplied to the UIDynamicAnimator




    [_animator addBehavior:_collision];


    UIDynamicItemBehavior *itemBehaviour = [[UIDynamicItemBehavior alloc] initWithItems:@[_square]];
    itemBehaviour.elasticity = 0.6;
    [_animator addBehavior:itemBehaviour];

    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    [_square addGestureRecognizer:gesture];

    UIAttachmentBehavior *attach = [[UIAttachmentBehavior alloc] initWithItem:_square2 attachedToItem:_square];
    [_animator addBehavior:attach];

}

-(void)handlePan:(UIPanGestureRecognizer *)gesture
{
    CGPoint touchPoint = [gesture locationInView:self.view];
    UIView* draggedView = gesture.view;

    if (gesture.state == UIGestureRecognizerStateBegan) {
        // 1. was the pan initiated from the upper part of the recipe?
        UIView* draggedView = gesture.view;
        CGPoint dragStartLocation = [gesture locationInView:draggedView];
            _draggingView = YES;
            _previousTouchPoint = touchPoint;
//            [_animator updateItemUsingCurrentState:draggedView];

    } else if (gesture.state == UIGestureRecognizerStateChanged && _draggingView) {
        // 2. handle dragging
        float xOffset = _previousTouchPoint.x - touchPoint.x;
        gesture.view.center = CGPointMake(draggedView.center.x - xOffset,
                                          draggedView.center.y);
        _previousTouchPoint = touchPoint;
//        [_animator updateItemUsingCurrentState:draggedView];

    } else if (gesture.state == UIGestureRecognizerStateEnded && _draggingView) {
        // 3. the gesture has ended
//        [self tryDockView:draggedView];
//        [self addVelocityToView:draggedView fromGesture:gesture];
        [_animator updateItemUsingCurrentState:draggedView];
        _draggingView = NO;
    }

}

Answer 1

您需要使用附件来拖动您的形状，以便动画师可以使用其物理引擎计算每个项目的位置。

这是你的 viewDidLoad 更新:

- (void)viewDidLoad
{
    [super viewDidLoad];

    _containmentView = [[UIView alloc] initWithFrame:CGRectMake(0.0, self.view.frame.size.height/2, self.view.frame.size.width, 200)];
    [self.view addSubview:_containmentView];
    [_containmentView setBackgroundColor:[UIColor greenColor]];

    _square = [[UIView alloc]initWithFrame:CGRectMake(200, 0, 100, 100)];
    _square.backgroundColor = [UIColor yellowColor];
    [_containmentView addSubview:_square];

    _square2 = [[UIView alloc]initWithFrame:CGRectMake(100, 0, 100, 100)];
    _square2.backgroundColor = [UIColor redColor];
    [_containmentView addSubview:_square2];

    _animator = [[UIDynamicAnimator alloc]initWithReferenceView:_containmentView];
    _gravity = [[UIGravityBehavior alloc]initWithItems:@[_square, _square2]];
    _gravity.gravityDirection = CGVectorMake(-1.0, 0.0);
    [_animator addBehavior:_gravity];

    _collision = [[UICollisionBehavior alloc]initWithItems:@[_square, _square2]];
    _collision.translatesReferenceBoundsIntoBoundary = YES;

    [_animator addBehavior:_collision];


    UIDynamicItemBehavior *itemBehaviour = [[UIDynamicItemBehavior alloc] initWithItems:@[_square, _square2]];
    itemBehaviour.elasticity = 0.6;
    [_animator addBehavior:itemBehaviour];

    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    [_square addGestureRecognizer:gesture];

    UIPanGestureRecognizer *gesture2 = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    [_square2 addGestureRecognizer:gesture2];

    UIAttachmentBehavior *attach = [[UIAttachmentBehavior alloc] initWithItem:_square2 attachedToItem:_square];
    attach.damping = 1.6;
    attach.frequency = 10;
    [_animator addBehavior:attach];

}

我为两种形状都添加了重力、平移和碰撞。

这里应该看看你的 handlePan 方法:

-(void)handlePan:(UIPanGestureRecognizer *)gesture
{
    CGPoint touchPoint = [gesture locationInView:_containmentView];
    UIView* draggedView = gesture.view;

    if (gesture.state == UIGestureRecognizerStateBegan) {
        // 1. was the pan initiated from the upper part of the recipe?
        _draggingView = YES;
        _previousTouchPoint = touchPoint;
        // Add a new attachment on the selected view;
        self.attachment = [[UIAttachmentBehavior alloc] initWithItem:draggedView attachedToAnchor:touchPoint];
        [self.animator addBehavior:self.attachment];
        // Could temporarily remove gravity here

    } else if (gesture.state == UIGestureRecognizerStateChanged && _draggingView) {
        // 2. handle dragging
        [self.attachment setAnchorPoint:touchPoint];

    } else if (gesture.state == UIGestureRecognizerStateEnded && _draggingView) {
        // 3. the gesture has ended
        _draggingView = NO;
        [self.animator removeBehavior:self.attachment];
        // If gravity was removed, add it back here
    }
}

您可能希望在拖动时暂时移除重力。看看我的评论，看看你可以在哪里做(并且不要忘记在拖动结束时把它放回去)。

如您所见，您确实需要更少的代码来以这种方式处理手势 :)。

您可以同时调整附件的阻尼、频率和长度，使形状对拖动手势做出不同的 react 。您还可以使用 UIDynamicItemBehavior 的 density 属性为形状添加密度。