模糊主要使用UIVisualEffectView，這只在ios8以后適用

//模糊的遮罩view @property(nonatomic,strong) UIVisualEffectView *effectView; @property(nonatomic,strong) CollectionviewLayout *layout;CollectionviewLayout *layout = [[CollectionviewLayout alloc]init]; layout.itemSize = CGSizeMake(mScreenWidth, 40); layout.headerReferenceSize = CGSizeMake(mScreenWidth, collectionViewHeaderHeight); self.layout = layout;

遮罩view的設置

UIBlurEffect *blur = [UIBlurEffect effectWithStyle:(UIBlurEffectStyleLight)]; UIVisualEffectView *effectView = [[UIVisualEffectView alloc] initWithEffect:blur]; effectView.alpha = 0; self.effectView = effectView; [_collectionView addSubview:_effectView];

header是UIImageView,大小為layout.headerReferenceSize
模糊是在-(void)scrollViewDidScroll:(UIScrollView *)scrollView中寫

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{CGFloat offSetY = scrollView.contentOffset.y;CGFloat deltaY = fabs(offSetY);if (offSetY < 0) {CGSize headerSize = [self.layout headerReferenceSize];CGRect headRect = CGRectZero;headRect.size.height = headerSize.height + deltaY;headRect.size.width = headerSize.width + deltaY;headRect.origin.y = headRect.origin.y - deltaY;headRect.origin.x = headRect.origin.x - deltaY/2;//UIVisualEffectView的frame應與header的ImageView的frame相同//上述headRect也為header的imageView的frameself.effectView.frame = headRect;self.effectView.alpha = deltaY/collectionViewHeaderHeight*1.5 ;} }

效果為

轉載于:https://www.cnblogs.com/Apologize/p/6306578.html

總結

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