IOSdrawRect实现雪花飘落效果

#import <UIKit/UIKit.h>@interface HHFSnowflakeFallingView : UIView/** * 快速创建一个雪花飘落效果的view * * @param bgImageName 背景图片的名称 * @param snowImageName 雪花图片的名称 * @param frame  frame * * @return 实例化的 雪花飘落效果的view */@property(nonatomic,strong) UIImageView *bgImageView;@property(nonatomic,copy) NSString *snowImgName;+ (instancetype) snowfladeFallingViewWithBackgroundImageName:(NSString *) bgImageName snowImageName:(NSString *)snowImageName initWithFrame:(CGRect)frame;+ //开始下雪- (void) beginShow;@end

#import "HHFSnowflakeFallingView.h"@implementation HHFSnowflakeFallingView/** * <#Description#> * * @param bgImageName bgImageName 背景图片 * @param snowImageName snowImageName 雪花图片 * @param frame   frame 视图的位置和大小 * * @return view  需要绘制的视图 */+ (instancetype) snowfladeFallingViewWithBackgroundImageName:(NSString *) bgImageName snowImageName:(NSString *)snowImageName initWithFrame:(CGRect)frame{ HHFSnowflakeFallingView *view = [[HHFSnowflakeFallingView alloc] initWithFrame:frame]; view.bgImageView.image = [UIImage imageNamed:bgImageName]; view.snowImgName = snowImageName; return view;}- (instancetype)initWithFrame:(CGRect)frame{ self = [super initWithFrame:frame]; if (self) {  self.clipsToBounds = YES;  //添加背景图片的imageview  self.bgImageView = [[UIImageView alloc] init];  self.bgImageView.frame = self.bounds;  self.bgImageView.contentMode = UIViewContentModeScaleAspectFill;  [self addSubview:self.bgImageView]; } return self;}//开始下雪- (void) beginShow{ //启动定时器,使得一直调用setNeedsDisplay从而调用- (void) drawRect:(CGRect )rect //不得手动调用- (void) drawRect:(CGRect )rect CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(setNeedsDisplay)]; //让定时器循环调用 [link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];}- (void) drawRect:(CGRect)rect { //控制雪花最多的个数 if (self.subviews.count >250) {  return; } //雪花的宽度 int width = arc4random() % 20; while (width < 5) {  width = arc4random() % 20; } //雪花的速度 int speed = arc4random() % 15; while (speed < 5) {  speed = arc4random() % 15; } //雪花起点y int startY = - (arc4random() % 100); //雪花起点x int startX = arc4random() % (int) [UIScreen mainScreen].bounds.size.width; //雪花终点x int endX = arc4random() % (int) [UIScreen mainScreen].bounds.size.width; UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:self.snowImgName]];  imageView.frame = CGRectMake(startX, startY, width, width); [self addSubview:imageView]; //设置动画 [UIView animateWithDuration:speed animations:^{  //设置雪花最终的frame  imageView.frame = CGRectMake(endX, [UIScreen mainScreen].bounds.size.height, width, width);  //设置雪花的旋转  imageView.transform = CGAffineTransformRotate(imageView.transform, M_PI);  //设置雪花透明度,使得雪花快落地的时候就像快消失的一样  imageView.alpha = 0.3; } completion:^(BOOL finished) {  [imageView removeFromSuperview]; }];}@end

#import "ViewController.h"#import "HHFSnowflakeFallingView.h"@interface ViewController ()@end@implementation ViewController- (void)viewDidLoad { [super viewDidLoad]; /**  雪花效果最主要的思路就是在于循环产生带雪花图片的imageView, 产生的雪花的imageview的 x、y、宽、下落的速度都是随机的，这个可以用随机数来产生数据。  */ self.navigationItem.title = @"雪花飘落效果"; //创建雪花飘落效果的view HHFSnowflakeFallingView *snowflakeFallingView = [HHFSnowflakeFallingView snowfladeFallingViewWithBackgroundImageName:@"snow_background" snowImageName:@"snow" initWithFrame:self.view.bounds]; //开始下雪 [snowflakeFallingView beginShow]; [self.view addSubview:snowflakeFallingView];}@end