今天的重点：利用ScrollView进行图片的缩放
直接先说原理吧--原理：利用了scrollview的回调函数（如下）以及scrollview自己内部的一些缩放规则（其实我也还没弄清楚具体scrollview干了什么事），只是知道了它可以怎么做-_-#
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
returnself.zoomImageView;
}
其实今天的缩放部分我还加上了常见的 双击图片的缩小与放大，先上代码：
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
//自身属性的一些设置
NSLog(@"%@",NSStringFromCGRect(frame));
self.delegate =self;
self.showsVerticalScrollIndicator =NO;
self.showsHorizontalScrollIndicator =NO;
self.maximumZoomScale =3;
//承载当前图片的imageview
self.zoomImageView = [[[UIImageViewalloc] init] autorelease];
self.zoomImageView.userInteractionEnabled =YES;
self.zoomImageView.frame =CGRectMake(0.0f, 0.0f, frame.size.width , frame.size.height);
self.zoomImageView.image = [UIImageimageNamed:@"lichengwu.jpeg"];
[self addSubview:self.zoomImageView];
// Add gesture,double tap zoom imageView.
UITapGestureRecognizer *doubleTapGesture = [[UITapGestureRecognizeralloc] initWithTarget:self
action:@selector(handleDoubleTap:)];
[doubleTapGesture setNumberOfTapsRequired:2];
[ self.zoomImageViewaddGestureRecognizer:doubleTapGesture];
[doubleTapGesture release];
// initialize tapclicks
tapClicks = NO;
}
return self;
}
接着上代码：
#pragma mark - Zoom methods
- (void)handleDoubleTap:(UIGestureRecognizer *)gesture
{
float newScale;
if (!tapClicks) {
newScale = self.zoomScale *2.0;
}
else{
newScale = self.zoomScale *0.0;
}
CGRect zoomRect = [selfzoomRectForScale:newScale withCenter:[gesturelocationInView:gesture.view]];
[self zoomToRect:zoomRectanimated:YES];
tapClicks = !tapClicks;
}
这一部分也是相当的一目了然，就是处理双击事件函数，是缩小还是放大，正正的处理图片的函数如下：
#pragma mark - CommonMethods
- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center
{
CGRect zoomRect;
zoomRect.size.height =self.frame.size.height / scale;
zoomRect.size.width =self.frame.size.width / scale;
zoomRect.origin.x = center.x - (zoomRect.size.width /2.0);
zoomRect.origin.y = center.y - (zoomRect.size.height /2.0);
return zoomRect;
}
看见原理了没，其实就是获得当前点击处的中心X与原来图片尺寸的差值，然后传递给Scrollview进行缩放，至于scrollview具体干了什么事情，这就要让喜欢刨根问底的童鞋用一些力气了，然后@给我哦。
