核心动画 - 红包雨

新建一个 xcode 项目，然后在 ViewController.m 编写代码实现效果。

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    //1. 设置CAEmitterLayer
    CAEmitterLayer * emitterLayer = [CAEmitterLayer layer];
    
    //2.在背景图上添加粒子图层
    [self.view.layer addSublayer:emitterLayer];
    
    //3.发射形状--线性
    emitterLayer.emitterShape = kCAEmitterLayerLine;
    emitterLayer.emitterMode = kCAEmitterLayerSurface;
    emitterLayer.emitterSize = self.view.frame.size;
    emitterLayer.emitterPosition = CGPointMake(self.view.frame.size.width * 0.5, -10);
    
    //2. 配置cell
    CAEmitterCell * emitterCell = [CAEmitterCell emitterCell];
    emitterCell.contents = (id)[UIImage imageNamed:@"hongbao"].CGImage;
    emitterCell.birthRate = 1.0f;
    emitterCell.lifetime = 30.0f;
    emitterCell.speed = 2.0f;
    emitterCell.velocity = 10.0f;
    emitterCell.velocityRange = 10.0f;
    emitterCell.yAcceleration = 60.0f;
    emitterCell.scale = 0.05f;
    emitterCell.scaleRange = 0.0f;
    
    emitterLayer.emitterCells = @[emitterCell];
}


@end

运行效果如下：

红包雨.png