iOS 7 之后新出來一個阻尼動畫璧尸，類似于彈簧效果的API:
+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay usingSpringWithDamping:(CGFloat)dampingRatio initialSpringVelocity:(CGFloat)velocity options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^ __nullable)(BOOL finished))completion NS_AVAILABLE_IOS(7_0);
dampingRatio（阻尼系數(shù)）
范圍 0~1 當它設(shè)置為1時供常，動畫是平滑的沒有振動的達到靜止狀態(tài)骇两，越接近0 振動越大
velocity （彈性速率）
就是形變的速度，從視覺上看可以理解彈簧的形變速度呻右，到動畫結(jié)束，該速度減為0，所以茂装，velocity速度越大怠蹂，那么形變會越快善延，當然在同等時間內(nèi)，速度的變化（就是速率）也會越快城侧，因為速度最后都要到0易遣。
效果：
動畫.gif
- (void)viewDidLoad {
[super viewDidLoad];
UIButton *button =[UIButton buttonWithType:UIButtonTypeCustom];
button.backgroundColor =[UIColor greenColor];
[button setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
[button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
[button setTitle:@"展開" forState:UIControlStateNormal];
[button setTitle:@"收起" forState:UIControlStateSelected];
button.frame = CGRectMake(Device_Width - 100, 200, 80, 40);
[button addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];
_label =[[UILabel alloc]initWithFrame:CGRectMake(Device_Width - 100, 200, 0, 40)];
_label.backgroundColor =[UIColor cyanColor];
_label.text = @"哈哈哈";
[self.view addSubview:_label];
}
-(void)btnClick:(UIButton *)button
{
button.selected = !button.selected;
if (button.selected) {
[UIView animateWithDuration:1 delay:0 usingSpringWithDamping:0.5 initialSpringVelocity:0.6 options:UIViewAnimationOptionCurveLinear animations:^{
_label.frame = CGRectMake(Device_Width - 300, 200, 100, 40 );
} completion:^(BOOL finished) {
}];
}
if (!button.selected) {
[UIView animateWithDuration:0.3 delay:0 usingSpringWithDamping:0.5 initialSpringVelocity:0.6 options:UIViewAnimationOptionCurveLinear animations:^{
_label.frame = CGRectMake(Device_Width - 100, 200, 0, 40 );
} completion:^(BOOL finished) {
}];
}
}
