IOSdrawRect实现雪花飘落效果

本文实例为大家分享了iosdrawrect实现雪花飘落效果的具体代码，供大家参考，具体内容如下

绘制原理：

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。

实现代码：

#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

运行效果:

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