相關(guān)文獻(xiàn)：
iOS CoreAnimation(一) - 基礎(chǔ)知識
iOS CoreAnimation(二) - CALayer/UIBezierPath
iOS CoreAnimation(三) - CAEmitterLayer粒子圖層

本文主要內(nèi)容：
1.了解CAEmitterLayer 類常?屬性與?法
2.了解CAEmitterCell 類常?屬性與?法
3.案例：實(shí)現(xiàn)發(fā)射粒子效果
4.案例：實(shí)現(xiàn)下雨場景
5.案例：實(shí)現(xiàn)QQ點(diǎn)贊效果

一、CAEmitterLayer常用屬性與方法

CAEmitterLayer的實(shí)現(xiàn)?性能的粒?引擎,被?來創(chuàng)建實(shí)現(xiàn)粒?動畫,?如煙霧,?,?等效果。

API_AVAILABLE(macos(10.6), ios(5.0), watchos(2.0), tvos(9.0))
@interface CAEmitterLayer : CALayer
// emitterCells 存放粒子類型
// 一個發(fā)射器可以存放多種的粒子類型，圓形/方形/星形...只需要告訴發(fā)射器即可
@property(nullable, copy) NSArray<CAEmitterCell *> *emitterCells;

// 產(chǎn)生粒子速率（默認(rèn)1.0）
@property float birthRate;

// 粒子的生命周期（默認(rèn)1.0）
@property float lifetime;

// 粒子發(fā)射源的位置，默認(rèn)(x:0, y:0, z:0)
@property CGPoint emitterPosition;
@property CGFloat emitterZPosition;

//發(fā)射源尺寸CAEmitterLayer實(shí)例的size/depth, 默認(rèn)(width:0, height:0, depth:0)
@property CGSize emitterSize;
@property CGFloat emitterDepth;

// 發(fā)射源的形狀：
/** 值：點(diǎn)形`point' (the default), 
       線形`line', 矩形`rectangle',
       圓形`circle', 
      3D立體矩形`cuboid'，
      3D立體圓形`sphere'.
*/
@property(copy) CAEmitterLayerEmitterShape emitterShape;

// 發(fā)射源模式:
/** 值：`points'點(diǎn)模式, 
       `outline'輪廓模式(發(fā)射點(diǎn)邊界發(fā)射出來), 
       `surface'表面模式
       `volume' 3D發(fā)射模式(the default).
*/
@property(copy) CAEmitterLayerEmitterMode emitterMode;

// 發(fā)射源渲染模式：
// 值：`unordered' (the default), `oldestFirst', `oldestLast', `backToFront' (i.e. sorted into Z order) and `additive'.
@property(copy) CAEmitterLayerRenderMode renderMode;

// 當(dāng)為true時，粒子被渲染成好像它們直接居住在層的超層的三維坐標(biāo)空間，而不是首先被平展到層的平面（默認(rèn)為NO）。
// 如果為true，則“filters”、“backgroundFilters”和陰影相關(guān)屬性的效果是未定義的。
@property BOOL preservesDepth;

// 乘以粒子定義的粒子速度(默認(rèn)為1.0)。
@property float velocity;

// 乘以粒子定義的粒子縮放(默認(rèn)為1.0)。
@property float scale;

// 乘以粒子定義的粒子自旋(默認(rèn)為1.0)。
@property float spin;

// 用于初始化隨機(jī)數(shù)生成器的種子(默認(rèn)為0)。
// 每一層都有自己的RNG狀態(tài)。對于均值為M，范圍為R的性質(zhì)，性質(zhì)的隨機(jī)值均勻分布在區(qū)間[M - R/2, M + R/2]內(nèi)。
@property unsigned int seed;
@end

二、CAEmitterCell常?屬性與?法

CAEmitterCell定義的粒子樣式。

API_AVAILABLE(macos(10.6), ios(5.0), watchos(2.0), tvos(9.0))
@interface CAEmitterCell : NSObject <NSSecureCoding, CAMediaTiming>
{
@private
  void *_attr[2];
  void *_state;
  uint32_t _flags;
}

// 創(chuàng)建實(shí)例
+ (instancetype)emitterCell;

// 粒子實(shí)現(xiàn)與CALayer定義的相同的屬性模型。
+ (nullable id)defaultValueForKey:(NSString *)key;
- (BOOL)shouldArchiveValueForKey:(NSString *)key;

// 粒子名稱，默認(rèn)為nil?？梢詷?gòu)造多種粒子樣式，通過name去區(qū)分。
@property(nullable, copy) NSString *name;

// 是否可用，控制是否呈現(xiàn)此發(fā)射器中的粒子。
@property(getter=isEnabled) BOOL enabled;

// 每秒創(chuàng)建的發(fā)射的粒子數(shù)量。默認(rèn)值0.0
// 產(chǎn)生率
@property float birthRate;

// 每個發(fā)射的粒子生命周期(以秒為單位)，指定為平均值和平均值的范圍。這兩個值默認(rèn)0.0
@property float lifetime; // 生命周期
@property float lifetimeRange; // 生命周期的范圍 

// 發(fā)射粒子的緯度(弧度為單位)，X軸與Z軸之間的夾角，默認(rèn)0.0
@property CGFloat emissionLatitude;
// 發(fā)射粒子的經(jīng)度(弧度為單位)，X軸與Y軸之間的夾角，默認(rèn)0.0
@property CGFloat emissionLongitude;

// 發(fā)射角度(弧度為單位)，默認(rèn)0.0。發(fā)射的物體均勻地分布在這個錐體上。
@property CGFloat emissionRange;

// 每個發(fā)射粒子平均速度，默認(rèn)為0.0
@property CGFloat velocity;
// 每個發(fā)射粒子速度范圍，默認(rèn)為0.0
@property CGFloat velocityRange;

// 應(yīng)用于發(fā)射粒子在對應(yīng)軸上的加速度矢量。默認(rèn)(0, 0, 0)
@property CGFloat xAcceleration;
@property CGFloat yAcceleration;
@property CGFloat zAcceleration;

/* The scale factor applied to each emitted object, defined as mean and
 * range about the mean. Scale defaults to one, range to zero.
 * Animatable. */
// 初始縮放比例，默認(rèn)1.0，比如一開始就放大2倍就寫2
@property CGFloat scale;
// 縮放范圍，默認(rèn)0.0
@property CGFloat scaleRange;
// 縮放速度
@property CGFloat scaleSpeed;

// 應(yīng)用于每個粒子的旋轉(zhuǎn)速度，定義為平均值和平均值的范圍。默認(rèn)為0。
@property CGFloat spin;
@property CGFloat spinRange;

/* The mean color of each emitted object, and the range from that mean
 * color. `color' defaults to opaque white, `colorRange' to (0, 0, 0,
 * 0). Animatable. */
// 粒子的顏色，默認(rèn)白色
@property(nullable) CGColorRef color;
// 以及粒子的顏色變化范圍，colorRange為(r:0, g:0, b:0, a:0)。
@property float redRange;
@property float greenRange;
@property float blueRange;
@property float alphaRange;
// 顏色變化速度，默認(rèn) (0, 0, 0, 0)
@property float redSpeed;
@property float greenSpeed;
@property float blueSpeed;
@property float alphaSpeed;

// 粒子內(nèi)容，默認(rèn)nil。通常是CGImageRef。
@property(nullable, strong) id contents;
// contents的大小，默認(rèn)為[0 0 1 1]
@property CGRect contentsRect;
// contents的縮放系數(shù)
@property CGFloat contentsScale;

// 渲染“contents”圖像時使用的過濾器參數(shù)。
@property(copy) NSString *minificationFilter;
@property(copy) NSString *magnificationFilter;
@property float minificationFilterBias;

// 粒子里面再套粒子，類似于tableViewCell里也能有tableView的Cell
@property(nullable, copy) NSArray<CAEmitterCell *> *emitterCells;

// 繼承屬性類似于layers。
@property(nullable, copy) NSDictionary *style;

@end

三、案例：實(shí)現(xiàn)發(fā)射粒子效果

#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) CAEmitterLayer * colorBallLayer;
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor blackColor];
    [self setupEmitter];
    
}

- (void)setupEmitter {
    UILabel * label = [[UILabel alloc] initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, 50)];
    [self.view addSubview:label];
    label.textColor = [UIColor whiteColor];
    label.text = @"輕點(diǎn)或拖動來改變發(fā)射源位置";
    label.textAlignment = NSTextAlignmentCenter;
    
    //1.創(chuàng)建發(fā)射源，類似于UITableView
    CAEmitterLayer *colorBallLayer = [CAEmitterLayer layer];
    [self.view.layer addSublayer:colorBallLayer];
    self.colorBallLayer = colorBallLayer;
    
    //發(fā)射源尺寸colorBallLayer的frame
    colorBallLayer.emitterSize = self.view.frame.size;
    //發(fā)射源形狀
    colorBallLayer.emitterShape = kCAEmitterLayerPoint;
    //發(fā)射模式
    colorBallLayer.emitterMode = kCAEmitterLayerPoints;
    //粒子發(fā)射的中心點(diǎn).
    colorBallLayer.emitterPosition = CGPointMake(self.view.layer.bounds.size.width, 0);
    
    //2.設(shè)置Cell(粒子的樣式)，類似于UITableViewCell
    CAEmitterCell *colorBallCell = [CAEmitterCell emitterCell];
    //粒子名稱
    colorBallCell.name = @"ccCell";
    //粒子的產(chǎn)生速率
    colorBallCell.birthRate = 20.0f;
    //粒子的生命周期
    colorBallCell.lifetime = 10.0f;
    //粒子速度
    colorBallCell.velocity = 40.0f;
    colorBallCell.velocityRange = 100.0;
    colorBallCell.yAcceleration = 15.0f; // 粒子在Y軸上的加速矢量
    
    // 發(fā)射粒子的緯度(弧度為單位)，X軸與Z軸之間的夾角，默認(rèn)0.0
    colorBallCell.emissionLatitude = M_PI;
    // 發(fā)射角度(弧度為單位)，默認(rèn)0.0。發(fā)射的物體均勻地分布在這個錐體上。
    colorBallCell.emissionRange = M_PI_4;
    
    colorBallCell.scale = 0.2;
    colorBallCell.scaleRange = 0.1;
    colorBallCell.scaleSpeed = 0.02;
    
    //粒子的內(nèi)容
    colorBallCell.contents = (id)[[UIImage imageNamed:@"circle_white"] CGImage]; // 一張圖片
    
    //顏色變化
    colorBallCell.color = [UIColor colorWithRed:0.5 green:0.0 blue:0.5 alpha:1.0].CGColor;
    //粒子顏色改變范圍
    colorBallCell.alphaRange = 0.8f;
    colorBallCell.redRange = 1.0f;
    colorBallCell.greenRange = 1.0f;
    
    //粒子變化的速度
    colorBallCell.blueSpeed = 1.0f;
    colorBallCell.alphaSpeed = -0.1;
    
    // 一個發(fā)射器可以存放多種的粒子類型，圓形/方形/星形...只需要告訴發(fā)射器即可
    colorBallLayer.emitterCells = @[colorBallCell];
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    CGPoint point = [self locationFromTouchEvent:event];
    [self setBallInPsition:point];
}

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    CGPoint point = [self locationFromTouchEvent:event];
    [self setBallInPsition:point];
}

/**
 * 獲取手指所在點(diǎn)
 */
- (CGPoint)locationFromTouchEvent:(UIEvent *)event{
    UITouch * touch = [[event allTouches] anyObject];
    return [touch locationInView:self.view];
}

/**
 * 移動發(fā)射源到某個點(diǎn)上
 */
- (void)setBallInPsition:(CGPoint)position{
    //創(chuàng)建基礎(chǔ)動畫(粒子放大過程)
    CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:@"emitterCells.colorBallCell.scale"];
    // 改變粒子的縮放 0.2->0.5
    anim.fromValue = @0.2;
    anim.toValue = @0.5f;
    anim.duration = 1.0;
    //變化模式: 線性變化,動畫是勻速發(fā)生
    anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    
    //移動粒子的發(fā)射位置runloop
    //事務(wù)性動畫,用來包裝隱式動畫
    [CATransaction begin];
    [CATransaction setDisableActions:YES];
    [self.colorBallLayer addAnimation:anim forKey:nil];
    [self.colorBallLayer setValue:[NSValue valueWithCGPoint:position] forKey:@"emitterPosition"];
    [CATransaction commit];
}
@end

四、案例：實(shí)現(xiàn)下雨場景

#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) CAEmitterLayer * rainLayer;
@property (nonatomic, weak) UIImageView * imageView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setupUI];
    [self setupEmitter];
}

- (void)setupUI {
    // 背景圖片
    UIImageView * imageView = [[UIImageView alloc]initWithFrame:self.view.frame];
    [self.view addSubview:imageView];
    self.imageView = imageView;
    imageView.image = [UIImage imageNamed:@"rain"];
    
    // 下雨按鈕
    UIButton * startBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    [self.view addSubview:startBtn];
    startBtn.frame = CGRectMake(20, self.view.bounds.size.height - 60, 80, 40);
    startBtn.backgroundColor = [UIColor whiteColor];
    [startBtn setTitle:@"雨停了" forState:UIControlStateNormal];
    [startBtn setTitle:@"下雨" forState:UIControlStateSelected];
    [startBtn setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [startBtn setTitleColor:[UIColor redColor] forState:UIControlStateSelected];
    [startBtn addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];
    
    // 雨量按鈕
    UIButton * rainBIgBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    [self.view addSubview:rainBIgBtn];
    rainBIgBtn.tag = 100;
    rainBIgBtn.frame = CGRectMake(140, self.view.bounds.size.height - 60, 80, 40);
    rainBIgBtn.backgroundColor = [UIColor whiteColor];
    [rainBIgBtn setTitle:@"下大點(diǎn)" forState:UIControlStateNormal];
    [rainBIgBtn setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [rainBIgBtn addTarget:self action:@selector(rainButtonClick:) forControlEvents:UIControlEventTouchUpInside];
    
    UIButton * rainSmallBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    [self.view addSubview:rainSmallBtn];
    rainSmallBtn.tag = 200;
    rainSmallBtn.frame = CGRectMake(240, self.view.bounds.size.height - 60, 80, 40);
    rainSmallBtn.backgroundColor = [UIColor whiteColor];
    [rainSmallBtn setTitle:@"太大了" forState:UIControlStateNormal];
    [rainSmallBtn setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [rainSmallBtn addTarget:self action:@selector(rainButtonClick:) forControlEvents:UIControlEventTouchUpInside];
}

- (void)buttonClick:(UIButton *)sender {
    if (!sender.selected) {
        sender.selected = !sender.selected;
        NSLog(@"雨停了");
        // 停止下雨
        [self.rainLayer setValue:@0.f forKeyPath:@"birthRate"];
        
    }else{
        sender.selected = !sender.selected;
        NSLog(@"開始下雨了");
        // 開始下雨
        [self.rainLayer setValue:@1.f forKeyPath:@"birthRate"];
    }
}

- (void)rainButtonClick:(UIButton *)sender {
    NSInteger rate = 1;
    CGFloat scale = 0.05;
    if (sender.tag == 100) {
        NSLog(@"下大了");
        if (self.rainLayer.birthRate < 30) {
            [self.rainLayer setValue:@(self.rainLayer.birthRate + rate) forKeyPath:@"birthRate"];
            [self.rainLayer setValue:@(self.rainLayer.scale + scale) forKeyPath:@"scale"];
        }
        
    }else if (sender.tag == 200) {
        NSLog(@"變小了");
        if (self.rainLayer.birthRate > 1) {
            [self.rainLayer setValue:@(self.rainLayer.birthRate - rate) forKeyPath:@"birthRate"];
            [self.rainLayer setValue:@(self.rainLayer.scale - scale) forKeyPath:@"scale"];
        }
    }
}

- (void)setupEmitter {
    // 1. 設(shè)置CAEmitterLayer
    CAEmitterLayer * rainLayer = [CAEmitterLayer layer];
    // 2.在背景圖上添加粒子圖層
    [self.imageView.layer addSublayer:rainLayer];
    self.rainLayer = rainLayer;
    
    //3.發(fā)射形狀--線性
    rainLayer.emitterShape = kCAEmitterLayerLine;
    //發(fā)射模式
    rainLayer.emitterMode = kCAEmitterLayerSurface;
    //發(fā)射源大小
    rainLayer.emitterSize = self.view.frame.size;
    //發(fā)射源位置 y最好不要設(shè)置為0 最好<0
    rainLayer.emitterPosition = CGPointMake(self.view.bounds.size.width * 0.5, -10);
    
    // 2. 配置cell
    CAEmitterCell * snowCell = [CAEmitterCell emitterCell];
    //粒子內(nèi)容
    snowCell.contents = (id)[[UIImage imageNamed:@"rain_white"] CGImage];
    //每秒產(chǎn)生的粒子數(shù)量的系數(shù)
    snowCell.birthRate = 25.f;
    //粒子的生命周期
    snowCell.lifetime = 20.f;
    //speed粒子速度.圖層的速率。用于將父時間縮放為本地時間，例如，如果速率是2，則本地時間的進(jìn)度是父時間的兩倍。默認(rèn)值為1。
    snowCell.speed = 10.f;
    //粒子速度系數(shù), 默認(rèn)1.0
    snowCell.velocity = 10.f;
    //每個發(fā)射物體的初始平均范圍,默認(rèn)等于0
    snowCell.velocityRange = 10.f;
    //粒子在y方向的加速的
    snowCell.yAcceleration = 1000.f;
    //粒子縮放比例: scale
    snowCell.scale = 0.1;
    //粒子縮放比例范圍:scaleRange
    snowCell.scaleRange = 0.f;
    
    // 3.添加到圖層上
    rainLayer.emitterCells = @[snowCell];
}
@end

五、案例：實(shí)現(xiàn)QQ點(diǎn)贊效果

• 點(diǎn)贊按鈕放大->縮?。篊AKeyFrameAnimation
• 放大之后，釋放一個圈的粒子效果：CAEmitterLayer

需要：1.自定義按鈕、2.重寫按鈕選中狀態(tài)、3.配置動畫

#import "ViewController.h"
#import "CCLikeButton.h"
@interface ViewController ()
@end

@implementation ViewController
- (void)viewDidLoad {
    
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    //添加點(diǎn)贊按鈕
    CCLikeButton * btn = [CCLikeButton buttonWithType:UIButtonTypeCustom];
    btn.frame = CGRectMake(200, 150, 30, 130);
    [self.view addSubview:btn];
    [btn setImage:[UIImage imageNamed:@"dislike"] forState:UIControlStateNormal];
    [btn setImage:[UIImage imageNamed:@"like_orange"] forState:UIControlStateSelected];
    [btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
}

- (void)btnClick:(UIButton *)button {
    if (!button.selected) { // 點(diǎn)贊
        button.selected = !button.selected;
        NSLog(@"點(diǎn)贊");
    }else{ // 取消點(diǎn)贊
        button.selected = !button.selected;
        NSLog(@"取消贊");
    }
}
@end

#import "CCLikeButton.h"
@interface CCLikeButton()
@property(nonatomic,strong)CAEmitterLayer *explosionLayer;
@end

@implementation CCLikeButton
- (void)awakeFromNib{
    [super awakeFromNib];
    //設(shè)置粒子效果
    [self setupExplosion];
}

- (instancetype)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self) {
        [self setupExplosion];
    }
    return self;
}

//設(shè)置粒子
- (void)setupExplosion {
    // 1. 粒子
    CAEmitterCell * explosionCell = [CAEmitterCell emitterCell];
    explosionCell.name = @"explosionCell";
    //透明值變化速度
    explosionCell.alphaSpeed = -1.f;
    //alphaRange透明值范圍
    explosionCell.alphaRange = 0.10;
    //生命周期
    explosionCell.lifetime = 1;
    //生命周期range
    explosionCell.lifetimeRange = 0.1;
    //粒子速度
    explosionCell.velocity = 40.f;
    //粒子速度范圍
    explosionCell.velocityRange = 10.f;
    //縮放比例
    explosionCell.scale = 0.08;
    //縮放比例range
    explosionCell.scaleRange = 0.02;
    //粒子圖片
    explosionCell.contents = (id)[[UIImage imageNamed:@"spark_red"] CGImage];
    
    // 2.發(fā)射源
    CAEmitterLayer * explosionLayer = [CAEmitterLayer layer];
    [self.layer addSublayer:explosionLayer];
    self.explosionLayer = explosionLayer;
    //發(fā)射院尺寸大小
    self.explosionLayer.emitterSize = CGSizeMake(self.bounds.size.width + 40, self.bounds.size.height + 40);
    //emitterShape表示粒子從什么形狀發(fā)射出來,圓形形狀
    explosionLayer.emitterShape = kCAEmitterLayerCircle;
    //emitterMode發(fā)射模型,輪廓模式,從形狀的邊界上發(fā)射粒子
    explosionLayer.emitterMode = kCAEmitterLayerOutline;
    //renderMode:渲染模式
    explosionLayer.renderMode = kCAEmitterLayerOldestFirst;
    //粒子cell 數(shù)組
    explosionLayer.emitterCells = @[explosionCell];
}


-(void)layoutSubviews {
    // 發(fā)射源位置
    self.explosionLayer.position = CGPointMake(self.bounds.size.width * 0.5, self.bounds.size.height * 0.5);
    
    [super layoutSubviews];
}

/**
 * 選中狀態(tài) 實(shí)現(xiàn)縮放
 */
- (void)setSelected:(BOOL)selected {
    [super setSelected:selected];
    
    // 通過關(guān)鍵幀動畫實(shí)現(xiàn)縮放
    CAKeyframeAnimation * animation = [CAKeyframeAnimation animation];
    // 設(shè)置動畫路徑
    animation.keyPath = @"transform.scale";
    
    if (selected) {
        // 從沒有點(diǎn)擊到點(diǎn)擊狀態(tài) 會有爆炸的動畫效果
        animation.values = @[@1.5,@2.0, @0.8, @1.0];
        animation.duration = 0.5;
        //計算關(guān)鍵幀方式:
        animation.calculationMode = kCAAnimationCubic;
        //為圖層添加動畫
        [self.layer addAnimation:animation forKey:nil];
        
        // 讓放大動畫先執(zhí)行完畢 再執(zhí)行爆炸動畫
        [self performSelector:@selector(startAnimation) withObject:nil afterDelay:0.25];
    }else{
        // 從點(diǎn)擊狀態(tài)normal狀態(tài) 無動畫效果 如果點(diǎn)贊之后馬上取消 那么也立馬停止動畫
        [self stopAnimation];
    }
}

// 沒有高亮狀態(tài)
- (void)setHighlighted:(BOOL)highlighted{
    [super setHighlighted:highlighted];
}

/**
 * 開始動畫
 */
- (void)startAnimation{
    
    // 用KVC設(shè)置顆粒個數(shù)
    [self.explosionLayer setValue:@1000 forKeyPath:@"emitterCells.explosionCell.birthRate"];
    
    // 開始動畫
    self.explosionLayer.beginTime = CACurrentMediaTime();
    
    // 延遲停止動畫
    [self performSelector:@selector(stopAnimation) withObject:nil afterDelay:0.15];
}

/**
 * 動畫結(jié)束
 */
- (void)stopAnimation{
    // 用KVC設(shè)置顆粒個數(shù)
    [self.explosionLayer setValue:@0 forKeyPath:@"emitterCells.explosionCell.birthRate"];
    //移除動畫
    [self.explosionLayer removeAllAnimations];
}

- (void)drawRect:(CGRect)rect {
    
}
@end