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Question

我正在使用CGRect创建一个图像帧。我想要对创建的矩形进行居中。

我在这里查看过，以及在苹果文档中找到了最好的方法，并找到了CGRectGetMidY和CGRectGetMidX，它们得到中心坐标。

当我尝试将其实现到我自己的代码中时，我会遇到一些问题。在UIIMageView错误类型的对象上找不到属性大小

       #import "MyViewController.h"



    @interface MyViewController ()

    @end

    @implementation MyViewController

    @synthesize mySignatureImage;
    @synthesize lastContactPoint1, lastContactPoint2, currentPoint;
    @synthesize imageFrame;
    @synthesize fingerMoved;
    @synthesize navbarHeight;

    - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
    {
        self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
        if (self) {
            // Custom initialization
        }
        return self;
    }

    - (void)viewDidLoad
    {
        [super viewDidLoad];



        self.view.backgroundColor = [UIColor lightGrayColor];

        CGRect mySignatureImageFrame = CGRectMake(
                                       CGRectGetMidX(self.view.frame) - (mySignatureImage.size.width/ 2.0),
                                       CGRectGetMidY(self.view.frame) - (mySignatureImage.size.height / 2.0),
                                       image.size.width,
                                       image.size.height);




#import <UIKit/UIKit.h>

@interface MyViewController : UIViewController <UIAlertViewDelegate>

@property (nonatomic, strong) UIImageView *mySignatureImage;
@property (nonatomic, assign) CGPoint lastContactPoint1, lastContactPoint2, currentPoint;
@property (nonatomic, assign) CGRect imageFrame;
@property (nonatomic, assign) BOOL fingerMoved;
@property (nonatomic, assign) float navbarHeight;


@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;

Answer 1

假设image是UIImage类型，那么：

CGRect imageFrame = CGRectMake(
    CGRectGetMidX(self.view.frame) - (image.size.width / 2.0),
    CGRectGetMidY(self.view.frame) - (image.size.height / 2.0),
    image.size.width,
    image.size.height);

假设imageView是UIImageView类型，那么：

CGRect imageFrame = CGRectMake(
    CGRectGetMidX(self.view.frame) - CGRectGetMidX(imageView.frame),
    CGRectGetMidY(self.view.frame) - CGRectGetMidY(imageView.frame),
    CGRectGetWidth(imageView.frame),
    CGRectGetHeight(imageView.frame));

Answer 2

您不需要计算中心点，因为它对于视图是可用的：

CGRect superviewBounds = superview.bounds;
imageView.center = CGPointMake(CGRectGetMidX(superviewBounds), CGRectGetMidY(superviewBounds));

Answer 3

- (void)viewDidAppear:(BOOL)animated {


img.center = CGPointMake(CGRectGetMidX([self.view bounds]), CGRectGetMidY([self.view   bounds]));
}

/*write code in viewDidApper */