說說今天遇到的UIKit力學問題

今天學到UIKit Dynamic的

Adding Gravity to Your UI Components 

想要實現下圖的效果

結果方塊一直是垂直下落不旋轉

- (void)viewDidAppear:(BOOL)animated

{

    [superviewDidAppear:animated];

    

   

    self.squareView = [[UIViewalloc]initWithFrame:CGRectMake(0.0f,0.0f,100.0f, 100.0f)];

    self.squareView.backgroundColor = [UIColorcyanColor];

    self.squareView.center =self.view.center;

    [self.viewaddSubview:self.squareView];

    

   

    self.animator = [[UIDynamicAnimatoralloc]initWithReferenceView:self.view];

    self.squareView.transform = CGAffineTransformRotate(self.squareView.transform,45);

    

    UIGravityBehavior *gravity = [[UIGravityBehavioralloc]initWithItems:@[self.squareView]];

    [self.animatoraddBehavior:gravity];

    

    UICollisionBehavior *collision = [[UICollisionBehavioralloc]initWithItems:@[self.squareView]];

    

   collision.translatesReferenceBoundsIntoBoundary =YES;

    [self.animatoraddBehavior:collision];

}

問題解決方式：是因爲我錯誤的把

self.squareView.transform = CGAffineTransformRotate(self.squareView.transform,45);

放在了

 UIGravityBehavior *gravity = [[UIGravityBehavior alloc]initWithItems:@[self.squareView]];

[self.animator addBehavior:gravity];

的後面，找了半天，經朋友提醒才知道問題是這樣的，應該是將圖片在經重力下落前就旋轉

總結：有時候邏輯上出了問題，就很難找出問題所在了