尝试使用 UIKit Dynamics 使 UIView 反弹

Question

我正在尝试使用 UIKit Dynamics "bounce" 获得一个圆形的 UIView。它应该在到达屏幕底部时反弹。圆圈是我在 viewDidLoad 方法中创建的标准 UIView，如下所示：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.orangeBall = [[UIView alloc] initWithFrame:CGRectMake(100.0, 100.0, 50.0, 50.0)];
    self.orangeBall.backgroundColor = [UIColor orangeColor];
    self.orangeBall.layer.cornerRadius = 25.0;
    self.orangeBall.layer.borderColor = [UIColor blackColor].CGColor;
    self.orangeBall.layer.borderWidth = 0.0;
    [self.view addSubview:self.orangeBall];

    // Initialize the property UIDynamicAnimator
    self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];

    [self demoGravity];

}

我正在尝试在 demoGravity 方法中实现弹跳效果，如下所示：

-(void)demoGravity{

UIGravityBehavior *gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[self.orangeBall]];

[self.animator addBehavior:gravityBehavior];

UICollisionBehavior *collisionBehavior = [[UICollisionBehavior alloc] initWithItems:@[self.orangeBall]];

[collisionBehavior addBoundaryWithIdentifier:@"myView"
                                   fromPoint:self.orangeBall.frame.origin
                                     toPoint:CGPointMake(self.orangeBall.frame.origin.x, self.orangeBall.frame.origin.y + self.view.frame.size.height)];

[self.animator addBehavior:collisionBehavior];
}

我想让 "ball" 直接落在屏幕上，一旦到达视图底部就停止，"bounce"。但是，当我运行我的应用程序时，我所看到的只是屏幕顶部的圆圈从屏幕上掉下来了。我做错了什么？

Answer 1

我的球不弹跳的原因有两个：

它没有掉落，因为我的 UIDynamicAnimator 对象没有附加 gravityBehaviour：

UIGravityBehavior *gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[self.orangeBall]];

[self.animator addBehavior:gravityBehavior];

它没有弹跳，因为我需要将 CollisionBehaviour: "TranslatesReferenceBoundsIntoBoundary" 的布尔值属性设置为 "YES"。
```
[collisionBehavior setTranslatesReferenceBoundsIntoBoundary:YES];
```

特别感谢 Ray Wenderlich，其中 article 为我提供了解决方案，以下段落是文章的直接引用：

Rather than explicitly adding boundary co-ordinates, the above code sets the translatesReferenceBoundsIntoBoundary property to YES. This causes the boundary to use the bounds of the reference view supplied to the UIDynamicAnimator.

尝试使用 UIKit Dynamics 使 UIView 反弹

Trying to get UIView to bounce using UIKit Dynamics

ios

objective-c

uiview

uikit-dynamics