生活中能够遇到很多应用有放大镜效果，那我们如何完成呢？
效果展示
* 别急，多说无益，上代码！*
首先我们要做的是建一个继承于UIWindow的类
我把它冠以我的名字缩写
WYHMagnifierView.h
/**************
* *
* 放大镜视图类 *
* *
*************/
#import <UIKit/UIKit.h>
@interface WYHMagnifierView : UIWindow
//放大框
@property(nonatomic,strong)UIView * magnifyView;
//触摸点
@property(nonatomic)CGPoint pointTomagnify;
@end
WYHMagnifierView.m
#import "WYHMagnifierView.h"
@interface WYHMagnifierView ()
@property (nonatomic, strong) CALayer *contentLayer;
@end
@implementation WYHMagnifierView
-(instancetype)init
{
self = [super init];
if (self) {
self.frame = CGRectMake(0, 0, 100, 50);
self.backgroundColor = [UIColor clearColor];
self.layer.borderWidth = 1;
self.layer.borderColor = [UIColor lightGrayColor].CGColor;
self.layer.cornerRadius = 5;
self.layer.masksToBounds = YES;
self.windowLevel = UIWindowLevelAlert;
self.contentLayer = [CALayer layer];
self.contentLayer.frame = self.bounds;
self.contentLayer.delegate = self;
self.contentLayer.contentsScale = [[UIScreen mainScreen] scale];
[self.layer addSublayer:self.contentLayer];
}
return self;
}
#pragma mark set the point of magnifier
-(void)setPointTomagnify:(CGPoint)pointTomagnify
{
_pointTomagnify = pointTomagnify;
CGPoint center = CGPointMake(pointTomagnify.x, self.center.y);
if (pointTomagnify.y > CGRectGetHeight(self.bounds) * 0.5) {
center.y = pointTomagnify.y - CGRectGetHeight(self.bounds)/2;
}
self.center = center;
[self.contentLayer setNeedsDisplay];
}
#pragma mark invoke by setNeedDisplay
-(void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx
{
float width = CGRectGetWidth(self.frame);
float height = CGRectGetHeight(self.frame);
//宽高
CGContextTranslateCTM(ctx,width * 0.5, height * 0.5);
//缩放比例
CGContextScaleCTM(ctx, 1.5, 1.5);
//x y 坐标转换
CGContextTranslateCTM(ctx, -self.pointTomagnify.x , -self.pointTomagnify.y - 20);
//截屏并显示
[self.magnifyView.layer renderInContext:ctx];
}
@end
ViewController.h
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@end
在ViewController的Storyboard上拉一个UILabel控件，
我写的text是王颜华————一个喜欢Photoshop的程序媛，backgroundColor设置的粉色，哈哈哈！
然后关联到下面的demoLabel属性。
ViewController.m
#import "ViewController.h"
#import "WYHMagnifierView.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *demoLabel;
//放大镜
@property (strong, nonatomic) CXYMagnifierView *magnifierView;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
UILongPressGestureRecognizer * pressGesTure = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(magniFierAction:)];
self.demoLabel.userInteractionEnabled = YES;
[self.demoLabel addGestureRecognizer:pressGesTure];
}
- (void)magniFierAction:(UILongPressGestureRecognizer *)gesture
{
NSLog(@"长按手势");
//获取手势位置
CGPoint point = [gesture locationInView:self.view];
switch (gesture.state) {
case UIGestureRecognizerStateBegan:
{
//设置放大镜位置
[self magnifierPosition:point];
//显示放大镜
[self.magnifierView makeKeyAndVisible];
break;
}
case UIGestureRecognizerStateChanged:
{
//设置放大镜位置
[self magnifierPosition:point];
break;
}
case UIGestureRecognizerStateEnded:
{
//长按结束取消放大镜
self.magnifierView.hidden = YES;
break;
}
default:
break;
}
}
-(void)magnifierPosition:(CGPoint )position
{
CGPoint point = position;
point.y -= 25;
position = point;
self.magnifierView.pointTomagnify = point;
}
#pragma mark lazy laod
-(CXYMagnifierView *)magnifierView
{
if (! _magnifierView) {
_magnifierView = [[CXYMagnifierView alloc]init];
_magnifierView.magnifyView = self.view.window;
}
return _magnifierView;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
@end