浅析IOS中播放gif动态图的方法

//要引入ImageIO库
#import <ImageIO/ImageIO.h>

//解析gif文件数据的方法 block中会将解析的数据传递出来
-(void)getGifImageWithUrk:(NSURL *)url
    returnData:(void(^)(NSArray<UIImage *> * imageArray,
        NSArray<NSNumber *>*timeArray,
        CGFloat totalTime,
        NSArray<NSNumber *>* widths,
        NSArray<NSNumber *>* heights))dataBlock{
 //通过文件的url来将gif文件读取为图片数据引用
 CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)url, NULL);
 //获取gif文件中图片的个数
 size_t count = CGImageSourceGetCount(source);
 //定义一个变量记录gif播放一轮的时间
 float allTime=0;
 //存放所有图片
 NSMutableArray * imageArray = [[NSMutableArray alloc]init];
 //存放每一帧播放的时间
 NSMutableArray * timeArray = [[NSMutableArray alloc]init];
 //存放每张图片的宽度 （一般在一个gif文件中，所有图片尺寸都会一样）
 NSMutableArray * widthArray = [[NSMutableArray alloc]init];
 //存放每张图片的高度
 NSMutableArray * heightArray = [[NSMutableArray alloc]init];
 //遍历
 for (size_t i=0; i<count; i++) {
  CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
  [imageArray addObject:(__bridge UIImage *)(image)];
  CGImageRelease(image);
  //获取图片信息
  NSDictionary * info = (__bridge NSDictionary*)CGImageSourceCopyPropertiesAtIndex(source, i, NULL);
  CGFloat width = [[info objectForKey:(__bridge NSString *)kCGImagePropertyPixelWidth] floatValue];
  CGFloat height = [[info objectForKey:(__bridge NSString *)kCGImagePropertyPixelHeight] floatValue];
  [widthArray addObject:[NSNumber numberWithFloat:width]];
  [heightArray addObject:[NSNumber numberWithFloat:height]];
  NSDictionary * timeDic = [info objectForKey:(__bridge NSString *)kCGImagePropertyGIFDictionary];
  CGFloat time = [[timeDic objectForKey:(__bridge NSString *)kCGImagePropertyGIFDelayTime]floatValue];
  allTime+=time;
  [timeArray addObject:[NSNumber numberWithFloat:time]];
  CFRelease(info);
 }
 CFRelease(source);
 dataBlock(imageArray,timeArray,allTime,widthArray,heightArray);
}

-(void)yh_setImage:(NSURL *)imageUrl{
  __weak id __self = self;
  [self getGifImageWithUrk:imageUrl returnData:^(NSArray<UIImage *> *imageArray, NSArray<NSNumber *> *timeArray, CGFloat totalTime, NSArray<NSNumber *> *widths, NSArray<NSNumber *> *heights) {
   //添加帧动画
   CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];
   NSMutableArray * times = [[NSMutableArray alloc]init];
   float currentTime = 0;
   //设置每一帧的时间占比
   for (int i=0; i<imageArray.count; i++) {
    [times addObject:[NSNumber numberWithFloat:currentTime/totalTime]];
    currentTime+=[timeArray[i] floatValue];
   }
   [animation setKeyTimes:times];
   [animation setValues:imageArray];
   [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
   //设置循环
   animation.repeatCount= MAXFLOAT;
   //设置播放总时长
   animation.duration = totalTime;
   //Layer层添加
   [[(UIImageView *)__self layer]addAnimation:animation forKey:@"gifAnimation"];
  }];
}

 UIImageView * imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0,0 , 320, 200)];
 NSURL * url = [[NSURL alloc]initFileURLWithPath:[[NSBundle mainBundle] pathForResource:imageName ofType:nil]];
 [imageView yh_setImage:url];
 [self.view addSubview:imageView];

 //读取gif数据
   NSData *gifData = [NSData dataWithContentsOfURL:imageUrl];
  UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
  //取消回弹效果
  webView.scrollView.bounces=NO;
  webView.backgroundColor = [UIColor clearColor];
  //设置缩放模式
  webView.scalesPageToFit = YES;
  //用webView加载数据
  [webView loadData:gifData MIMEType:@"image/gif" textEncodingName:nil baseURL:nil];