iOS UIDynamic简介 —— HERO博客

UIDynamic简介：

UIDynamic是从iOS 7开始引入的一种技术，是UIKit提供的非常方便的API，类似物理引擎效果，可以模仿重力、碰撞、反弹等效果。

UIDynamic包含几个主要属性：

1. 行为：

UIGravityBehavior：重力行为

UICollisionBehavior：碰撞行为

UISnapBehavior：捕捉行为

UIPushBehavior：推动行为

UIAttachmentBehavior：附着行为

UIDynamicItemBehavior：动力元素行为

2. 对象：

遵守了UIDynamicItem协议的对象，如UIView、UICollectionViewLayoutAttributes类默认已经遵守了UIDynamicItem协议，因此任何UI控件都能做物理仿真。

3.物理仿真器：

让对象执行仿真行为。

UIDynamic使用：

写了个小列子，简单说明一下UIDynamic的使用，先看一下效果图：



下面贴上代码：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

#import "ViewController.h"

#define mainW [UIScreen mainScreen].bounds.size.width
#define mainH [UIScreen mainScreen].bounds.size.height

@interface ViewController ()

@property (nonatomic, strong) UIDynamicAnimator *animator;
@property (nonatomic, weak) UIView *redView;
@property (nonatomic, weak) UIView *yellowView;
@property (nonatomic, weak) UIView *greenView;
@property (nonatomic, weak) UIView *blueView;

@end

@implementation ViewController

- (UIDynamicAnimator *)animator
{
if (_animator == nil) {
//创建物理仿真器
_animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
}
return _animator;
}

- (void)viewDidLoad {
[super viewDidLoad];

self.view.backgroundColor = [UIColor blackColor];

//创建控件
[self creatControl];
}

- (void)creatControl
{
UIView *blueView = [[UIView alloc] initWithFrame:CGRectMake((mainW - 51) * 0.5, mainH - 51, 51, 51)];
for (int i = 0; i < 51; i++) {
UIView *line = [[UIView alloc] initWithFrame:CGRectMake(26 - i, i, 2 * i + 1, 1)];
line.backgroundColor = [UIColor blueColor];
[blueView addSubview:line];
}
[self.view addSubview:blueView];
self.blueView = blueView;

UIView *yellowView = [[UIView alloc] initWithFrame:CGRectMake((mainW - 200) * 0.5, CGRectGetMinY(blueView.frame) - 20, 200, 20)];
yellowView.backgroundColor = [UIColor yellowColor];
[self.view addSubview:yellowView];
self.yellowView = yellowView;

UIView *greenView = [[UIView alloc] initWithFrame:CGRectMake(CGRectGetMinX(yellowView.frame), CGRectGetMinY(yellowView.frame) - 40, 40, 40)];
greenView.backgroundColor = [UIColor greenColor];
greenView.layer.cornerRadius = 20;
greenView.clipsToBounds = YES;
[self.view addSubview:greenView];
self.greenView = greenView;

UIView *redView = [[UIView alloc] initWithFrame:CGRectMake(CGRectGetMaxX(yellowView.frame) - 50, CGRectGetMinY(yellowView.frame) - 50, 50, 50)];
redView.backgroundColor = [UIColor redColor];
[self.view addSubview:redView];
self.redView = redView;

UIButton *resetBtn = [[UIButton alloc] initWithFrame:CGRectMake((mainW - 100) * 0.5, 50, 100, 30)];
resetBtn.backgroundColor = [UIColor orangeColor];
[resetBtn setTitle:@"重置" forState:UIControlStateNormal];
[resetBtn addTarget:self action:@selector(resetBtnOnClick) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:resetBtn];
}

- (void)resetBtnOnClick
{
for (UIControl *control in self.view.subviews) {
[control removeFromSuperview];
}
[self creatControl];
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
//获取一个触摸点
UITouch *touch = [touches anyObject];
CGPoint point = [touch locationInView:self.view];
//创建捕捉行为
UISnapBehavior *snap = [[UISnapBehavior alloc] initWithItem:self.redView snapToPoint:point];
//设置防震系数（0~1，数值越大，震动的幅度越小）
snap.damping = 0.5;
//删除之前的所有仿真行为
[self.animator removeAllBehaviors];
//执行捕捉行为
[self.animator addBehavior:snap];
//设置0.5秒延时执行
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.5f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
//重力碰撞
[self GravityCollisionStart];
});
}

-(void)GravityCollisionStart
{
//重力行为
UIGravityBehavior *gravity = [[UIGravityBehavior alloc] init];
//设置重力的加速度，重力的加速度越大，碰撞就越厉害
gravity.magnitude = 10;
//设置重力的方向（水平，垂直）
gravity.gravityDirection = CGVectorMake(0, 10);
[gravity addItem:self.redView];
//碰撞行为
UICollisionBehavior *collision = [[UICollisionBehavior alloc] init];
[collision addItem:self.redView];
[collision addItem:self.yellowView];
[collision addItem:self.greenView];
[collision addItem:self.blueView];
//让参照视图的边框成为碰撞检测的边界
collision.translatesReferenceBoundsIntoBoundary = YES;
//执行仿真
[self.animator removeAllBehaviors];
[self.animator addBehavior:gravity];
[self.animator addBehavior:collision];
}

@end