QQ空间的下拉放大图片

QQ空间的下拉放大图片 其实原理 很简单 只需要改变下网络或者本地加载图片的frame即可，

首先 创建一个新的类，继承于UIView，同时写几个方法

//初始化图片

- (instancetype)initWithFrame:(CGRect)frame withImages:(NSString *)imageName;

//加载网络图片 图片拉伸

- (instancetype) initWithFrame:(CGRect)frame WithImages:(NSURL *)imageUrl PlaceholderImage:(UIImage *)placeholder;

//图片放的的方法

- (void)imageViewStretchingWithOffSet:(CGFloat)offset;

当然、.m里面实现这三个方法

//初始化图片

- (instancetype)initWithFrame:(CGRect)frame withImages:(NSString *)imageName

{

self = [super initWithFrame:frame];

if (self) {

UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];

imageView.image = [UIImage imageNamed:imageName];

self.localImageView = imageView;

self.orginWidth = imageView.frame.size.width;

self.orginHeight = imageView.frame.size.height;

self.isLocal = localImage;

[self addSubview:imageView];

}

return self;

}

//加载网络图片 图片拉伸

- (instancetype) initWithFrame:(CGRect)frame WithImages:(NSURL *)imageUrl PlaceholderImage:(UIImage *)placeholder

{

self = [super initWithFrame:frame];

if (self) {

UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];

[imageView sd_setImageWithURL:imageUrl placeholderImage:placeholder];

self.netImageView = imageView;

self.orginWidth = imageView.frame.size.width;

self.orginHeight = imageView.frame.size.height;

self.isLocal = netImage;

[self addSubview:imageView];

}

return self;

}

//图片放的的方法

- (void)imageViewStretchingWithOffSet:(CGFloat)offset

{

CGFloat whPercent = self.orginWidth/self.orginHeight;//原始比例

CGFloat height = self.orginHeight - offset;//拉伸后的高度

CGFloat width = self.orginWidth - offset * whPercent;//拉伸后的宽度

if (offset < -1) {

if (self.isLocal == localImage) {

self.localImageView.frame = CGRectMake(offset/3*2, offset, width, height);

}

if (self.isLocal == netImage) {

self.netImageView.frame = CGRectMake(offset/3*2, offset, width, height);

}

}

else {

if (self.isLocal == localImage) {

self.localImageView.frame = CGRectMake(0, 0, self.orginWidth, self.orginHeight);

}

if (self.isLocal == netImage) {

self.netImageView.frame = CGRectMake(0, 0, self.orginWidth, self.orginHeight);

}

}

}

然后， 我们在ViewController里面创建视图视图继承于 创建的类

在ViewController.m里面 调用ScrollView的方法

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

CGFloat offsetY = scrollView.contentOffset.y;

if (offsetY < -1) {

if (offsetY > -100) {

//修改本地

[self.netImageView imageViewStretchingWithOffSet:offsetY];

self.NavbgImg.hidden = YES;

}

}

//导航栏

if (offsetY > -19) {

if (offsetY < 210) {

self.NavbgImg.hidden = NO;

self.NavbgImg.backgroundColor = [UIColor colorWithRed:0.5 green:0.5 blue:0.8 alpha:offsetY / 210];

} else {

self.NavbgImg.backgroundColor = [UIColor colorWithRed:0.5 green:0.5 blue:0.8 alpha:1];

self.NavbgImg.hidden = NO;

}

} else {

self.NavbgImg.hidden = YES;

}

}

即可 ，当然此处的导航栏也需要自定义的，

到此为止，下拉放大图片就完成了，如果有什么错误，希望大家多多指教，小弟不胜感激！！！