粒子效果

1.DrawView.h

#import 

@interface DrawView : UIView
- (void)startAnim;

- (void)reDraw;
@end

2.DrawView.m

#import "DrawView.h"

@interface DrawView ()

@property (nonatomic, strong) UIBezierPath *path;

@property (nonatomic, weak) CALayer *dotLayer;

@property (nonatomic, weak) CAReplicatorLayer *repL;


@end

@implementation DrawView

#pragma mark - 懒加载点层
- (CALayer *)dotLayer
{
    if (_dotLayer == nil) {
        // 创建图层
        CALayer *layer = [CALayer layer];
        
        CGFloat wh = 10;
        layer.frame = CGRectMake(0, -1000, wh, wh);
        
        layer.cornerRadius = wh / 2;
        
        layer.backgroundColor = [UIColor blueColor].CGColor;
        [_repL addSublayer:layer];
        
        _dotLayer = layer;
    }
    return _dotLayer;
}

- (UIBezierPath *)path
{
    if (_path == nil) {
        _path = [UIBezierPath bezierPath];
    }
    
    return _path;
}
#pragma mark - 开始点击调用
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    
    // 获取touch对象
    UITouch *touch = [touches anyObject];
    
    // 获取当前触摸点
    CGPoint curP = [touch locationInView:self];
    
    
    // 设置起点
    [self.path moveToPoint:curP];
    
    
    
}

static int _instansCount = 0;
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    // 获取touch对象
    UITouch *touch = [touches anyObject];
    
    // 获取当前触摸点
    CGPoint curP = [touch locationInView:self];

    // 添加线到某个点
    [_path addLineToPoint:curP];
    
    // 重绘
    [self setNeedsDisplay];
    
    _instansCount ++;
    
}


// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
    
    [_path stroke];
}

#pragma mark - 开始动画
- (void)startAnim
{

    // 创建帧动画
    CAKeyframeAnimation *anim = [CAKeyframeAnimation animation];
    
    anim.keyPath = @"position";
    
    anim.path = _path.CGPath;
    
    anim.duration = 3;
    
    anim.repeatCount = MAXFLOAT;
    
    [self.dotLayer addAnimation:anim forKey:nil];
    
    // 注意:如果复制的子层有动画，先添加动画，在复制
    // 复制子层
    _repL.instanceCount = _instansCount;
    
    // 延迟图层动画
    _repL.instanceDelay = 0.2;
    
}

#pragma mark - 加载完xib调用，创建复制层
- (void)awakeFromNib
{
    // 创建复制层
    CAReplicatorLayer *repL = [CAReplicatorLayer layer];
    
    repL.frame = self.bounds;
    
    [self.layer addSublayer:repL];
  
    _repL = repL;
}
#pragma mark - 重绘
- (void)reDraw
{
    // 清空绘图信息
    _path = nil;
    [self setNeedsDisplay];
    
    // 把图层移除父控件，复制层也会移除。
     [_dotLayer removeFromSuperlayer];
    _dotLayer = nil;

    // 清空子层总数
    _instansCount = 0;
    
}




@end