如何设置 UIImageView 大小以及如何确保它始终保持该大小？

Question

我一直在使用这个库在 iOS 上试验增强现实：https://github.com/promet/PRAugmentedReality

我添加了另一个名为“POIDetails”的 xib，用于显示我的兴趣点的详细信息。我通过这段代码添加了一个返回相机屏幕的按钮：

[self dismissViewControllerAnimated:self completion:nil];

但是当我返回 AR 屏幕时，POI 图像变得巨大。

我尝试将高度约束设置为 50，将纵横比设置为 1:1，但这并没有起到任何作用。我尝试像这样使用 sizeThatFits：

[myPOI sizeThatFits:CGSizeMake(50, 50)];

但它也没有用。在看到没有区别后，我将我在图像大小上所做的一切都放回去了。

您可以在下面看到之前和之后的图片以及用于下载我的项目的 google drive 链接。我怎样才能确保这张图片不会超出 50 像素的高度？

链接：https://drive.google.com/file/d/0B-cDfWHidgvcVVFRNll0OVR2UTA/view?usp=sharing

这是我的 ARObject.m 文件

#import "ARObject.h"
#import "POIDetails.h"


@interface ARObject ()

@end


@implementation ARObject

@synthesize arTitle, distance;

- (id)initWithId:(int)newId
           title:(NSString*)newTitle
     coordinates:(CLLocationCoordinate2D)newCoordinates
andCurrentLocation:(CLLocationCoordinate2D)currLoc
{
    self = [super init];
    if (self) {
        arId = newId;

        arTitle = [[NSString alloc] initWithString:newTitle];

        lat = newCoordinates.latitude;
        lon = newCoordinates.longitude;

        distance = @([self calculateDistanceFrom:currLoc]);

        [self.view setTag:newId];
    }
    return self;
}

-(double)calculateDistanceFrom:(CLLocationCoordinate2D)user_loc_coord
{
    CLLocationCoordinate2D object_loc_coord = CLLocationCoordinate2DMake(lat, lon);

    CLLocation *object_location = [[CLLocation alloc] initWithLatitude:object_loc_coord.latitude
                                                              longitude:object_loc_coord.longitude];
    CLLocation *user_location = [[CLLocation alloc] initWithLatitude:user_loc_coord.latitude
                                                            longitude:user_loc_coord.longitude];

    return [object_location distanceFromLocation:user_location];
}
-(NSString*)getDistanceLabelText
{
    if (distance.doubleValue > POINT_ONE_MILE_METERS)
         return [NSString stringWithFormat:@"%.2f mi", distance.doubleValue*METERS_TO_MILES];
    else return [NSString stringWithFormat:@"%.0f ft", distance.doubleValue*METERS_TO_FEET];
}

- (NSDictionary*)getARObjectData
{
    NSArray *keys = @[@"id",@"title", @"latitude", @"longitude", @"distance"];

    NSArray *values = @[@(arId),
                       arTitle,
                       @(lat),
                       @(lon),
                       distance];
    return [NSDictionary dictionaryWithObjects:values forKeys:keys];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    [titleL setText:arTitle];

    [distanceL setText:[self getDistanceLabelText]];
}

-(void)myPOITapping:(UIGestureRecognizer *)recognizer
{
    NSLog(@"image click");
    POIDetails *poiDetails = [[POIDetails alloc] initWithNibName:@"POIDetails" bundle:nil]; // constructor
    [self presentViewController:poiDetails animated:YES completion:nil];
}

// viewDidLoad wasn't in the library, timur added this method
- (void)viewDidLoad {
    myPOI.contentMode = UIViewContentModeScaleToFill;
    myPOI.translatesAutoresizingMaskIntoConstraints=YES;

    [myPOI setUserInteractionEnabled:YES];
    UITapGestureRecognizer *myPOITap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(myPOITapping:)];
    [myPOITap setNumberOfTapsRequired:1];
    [myPOI addGestureRecognizer:myPOITap];
    [self.view addSubview:myPOI];
}

#pragma mark -- OO Methods

- (NSString *)description {
    return [NSString stringWithFormat:@"ARObject %d - %@ - lat: %f - lon: %f - distance: %@",
            arId, arTitle, lat, lon, distance];
}

@end

---

编辑：

我在我的 ARObject.m 文件的 viewDidLoad 函数中添加了以下代码，它似乎将图像保持在设定的分辨率。

myPOI.contentMode = UIViewContentModeScaleToFill; myPOI.translatesAutoresizingMaskIntoConstraints=YES;

但我的距离标签仍然存在问题。我将顶部和底部间距约束设置为最近的邻居，标签现在是一半，但仍与我的兴趣点图像分开，如下所示：

---

---

---

之前：

之后：

Answer 1

我尝试将高度约束设置为 50，将纵横比设置为 1:1，但这没有任何好处

当您使用约束时，检查您的UIImageView 实例的translatesAutoresizingMaskIntoConstraints 属性是否设置为NO。

同时检查UIImageView的实例contentMode属性是否设置为UIViewContentModeScaleToFill

---

ARObject.m

CGRect myRect;

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    /*
     keep existed in this method code
    */

    /*
     move [self.view addSubview:myPOI] line to here, leave all other in viewDidLoad 
    */

    if (myRect.size.height != 0) {self.view.frame = myRect;}
    [self.view addSubview:myPOI];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    myRect = self.view.frame;
    [myPOI removeFromSuperview];
}

- (void)viewDidLoad
{
    myRect = CGRectZero;

    /*
     all your other code
    */    
}

很遗憾，我无法测试代码，因为此项目需要设备。