iOS 雪花效果

標籤：

1.transform屬性介紹

在OC中，通過transform屬性可以修改對象的平移、縮放比例和旋轉角度

常用的建立transform結構體方法分兩大類

  （1） 建立“基於控制項初始位置”的形變

　　CGAffineTransformMakeTranslation（平移）

　　CGAffineTransformMakeScale（縮放）

　　CGAffineTransformMakeRotation（旋轉)

 （2） 建立“基於transform參數”的形變

　　CGAffineTransformTranslate

　　CGAffineTransformScale

　　CGAffineTransformRotate

 2. 代碼實現

#import "ViewController.h"#define degree2angle(angle)  ((angle) * M_PI / 180)
@interface ViewController ()@property (nonatomic, strong) CADisplayLink *timer;@property (nonatomic ,assign) long long steps;@end@implementation ViewController- (CADisplayLink *)timer{    if (_timer == nil) {        _timer = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];    }    return _timer;}- (void)loadView{    UIImageView *bg = [[UIImageView alloc]initWithFrame:[UIScreen mainScreen].bounds];    bg.image = [UIImage imageNamed:@"snowbg.jpg"];    bg.contentMode = UIViewContentModeScaleAspectFill;    bg.userInteractionEnabled = YES;    self.view = bg;}
- (void)viewDidLoad {    [super viewDidLoad];    [self.timer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];}
//點擊的時候動畫停止- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{    [self stopTimer];}- (void)stopTimer{    [self.timer invalidate];}- (void)update{    _steps++;    //執行5次添加一次    if (_steps % 5 == 0) {        [self snow];    }}// 隱藏狀態列- (BOOL)prefersStatusBarHidden{    return YES;}//方法一 用transform屬性設定/*- (void)snow{    // 1.執行個體化一個雪花的映像視圖    UIImage *image = [UIImage imageNamed:@"雪花"];    UIImageView *imageView = [[UIImageView alloc]initWithImage:image];    // 0.1~0.4 隨機在0.01~0.4縮放    CGFloat scale = arc4random_uniform(40)/100.0 + 0.01;    // 設定雪花縮放    imageView.transform = CGAffineTransformMakeScale(scale, scale);
    CGSize winSize = self.view.bounds.size;
    // 2.添加到視圖    CGFloat x = arc4random_uniform(winSize.width);    CGFloat y = -imageView.bounds.size.height * 0.5;    imageView.center = CGPointMake(x, y);    [self.view addSubview:imageView];        // 3.動畫下落    [UIView animateWithDuration:10.0f animations:^{        // 移動到終點位置        CGFloat toX = arc4random_uniform(winSize.width);        CGFloat toY = winSize.height + imageView.bounds.size.height * 0.5;        imageView.center = CGPointMake(toX, toY);                // 下過過程中,設定雪花360度隨機旋轉        imageView.transform = CGAffineTransformRotate(imageView.transform, degree2angle(arc4random_uniform(360)));        imageView.alpha = 0.3;    } completion:^(BOOL finished) {        [imageView removeFromSuperview];    }];}*/ //方法二 用kvc設定- (void)snow{    // 1.執行個體化一個雪花的映像視圖    // 整個視圖的尺寸    CGSize winSize = self.view.bounds.size;    UIImage *image = [UIImage imageNamed:@"雪花"];
    // 2.添加到視圖    UIImageView *imageView = [[UIImageView alloc]initWithImage:image];    CGFloat startX = arc4random_uniform(winSize.width);    CGFloat startY = -imageView.bounds.size.height;    imageView.center = CGPointMake(startX, startY);    // 0.01~0.4 隨機在0.01~0.4縮放    CGFloat scale = arc4random_uniform(40)/100.0 + 0.01;    [imageView.layer setValue:@(scale) forKeyPath:@"transform.scale"];    [self.view addSubview:imageView];        //3.動畫下落    [UIView animateWithDuration:10.0f animations:^{        // 移動到終點位置    CGFloat endX = arc4random_uniform(winSize.width);    CGFloat endY = winSize.height + imageView.bounds.size.height;    imageView.center = CGPointMake(endX, endY);        // 下落的過程中旋轉180度    [imageView.layer setValue:@(M_PI) forKeyPath:@"transform.rotation"];        // 不透明度為0.3    [imageView.layer setValue:@(0.3) forKeyPath:@"opacity"];    } completion:^(BOOL finished) {        // 結束動畫移除imageView    [imageView removeFromSuperview];     }]; }@end

 

iOS 雪花效果