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ScrollView双击图片定点放大

2024-07-25 05:26:22   221人阅读

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;}
#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。

ScrollView双击图片定点放大


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