子供の本にドロップスの歌っていうのが載っていたので、ドロップが上から降ってくるようなiPhoneアプリのサンプルを描いてみます。今回はUIDynamicAnimatorというのを使ってみました。（※clearボタン付けたのですが、オブジェクト消すときにシミュレータだとメモリリークする気がします、UIDynamicAnimator使ったときのメモリ解放の作法が知りたい。。）
サンプルを動かすとこんな感じです
サンプルコード
#import “ViewController.h”
@interface ViewController () <UIDynamicAnimatorDelegate>
@property (strong, nonatomic) UIDynamicAnimator *animator;
@property (strong, nonatomic) UIGravityBehavior *gravity;
@property (strong, nonatomic) UICollisionBehavior *collider;
@property (weak, nonatomic) UIView *drop;
@end
@implementation ViewController
– (void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor blackColor];
[self setup];
}
– (void)setup
{
[self.animator addBehavior:self.gravity];
[self.animator addBehavior:self.collider];
UIButton *clear = [UIButton buttonWithType:UIButtonTypeSystem];
clear.frame = CGRectMake(10, 30, 60, 20);
clear.titleLabel.font = [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];
[clear setTitle:@”clear” forState:UIControlStateNormal];
[self.view addSubview:clear];
[clear addTarget:self action:@selector(clear) forControlEvents:UIControlEventTouchUpInside];
}
– (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint p = [[touches anyObject] locationInView:self.view];
UIView *drop = [[UIView alloc] initWithFrame:(CGRect){.size = CGSizeMake(5, 5)}];
drop.center = p;
float hue = (arc4random() % 10) / 10.0;
drop.backgroundColor = [UIColor colorWithHue:hue saturation:0.6 brightness:1.0 alpha:1.0];
drop.layer.masksToBounds = YES;
[self.view addSubview:drop];
self.drop = drop;
}
– (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint p = [[touches anyObject] locationInView:self.view];
CGPoint p0 = self.drop.center;
float r = hypotf(p.x – p0.x, p.y – p0.y);
self.drop.frame = CGRectMake(0, 0, r, r);
self.drop.center = p0;
self.drop.layer.cornerRadius = r/2.0;
}
– (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[self.gravity addItem:self.drop];
[self.collider addItem:self.drop];
}
– (UIDynamicAnimator *)animator
{
if (!_animator) {
_animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
_animator.delegate = self;
}
return _animator;
}
– (UIGravityBehavior *)gravity
{
if (!_gravity) {
_gravity = [[UIGravityBehavior alloc] init];
_gravity.magnitude = 0.9;
}
return _gravity;
}
– (UICollisionBehavior *)collider
{
if (!_collider) {
_collider = [[UICollisionBehavior alloc] init];
_collider.translatesReferenceBoundsIntoBoundary = YES;
}
return _collider;
}
– (void)clear
{
for (int i=0; i<[self.gravity.items count]; i++) {
[self.gravity removeItem:self.gravity.items[i]];
[self.collider removeItem:self.collider.items[i]];
}
[self.animator removeAllBehaviors];
[self.view.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
self.gravity = nil;
self.collider = nil;
self.animator = nil;
[self setup];
}
– (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end