自定义代表不响应iOS

Question

I've setup a delegate to take the old and new position of a gauge. However, I can't seem to get a response from the delegate. I could be missing something but I've done a bunch of research and it seems like everything is in order.

MeterView.h

#import <UIKit/UIKit.h>
#import "KTOneFingerRotationGestureRecognizer.h"

@protocol MeterViewDelegate;


@interface MeterView : UIView{

    IBOutlet UIImageView *gauge;
    IBOutlet UIImageView *needle;
    float rotation, oldPos, newPos;
    KTOneFingerRotationGestureRecognizer *rgest;
}

@property (nonatomic, weak) id<MeterViewDelegate> delegate;

- (IBAction)handleMovedNeedle;

@end

@protocol MeterViewDelegate <NSObject>

- (void)meterView:(MeterView*)view OldValue:(float)oldval NewValue:(float)newval;

@end

MeterView.m

#import "MeterView.h"
#import <QuartzCore/QuartzCore.h>


@implementation MeterView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {

    }
    return self;
}

-(void)handleMovedNeedle{
    if ([self.delegate respondsToSelector:@selector(meterView:OldValue:NewValue:)]) {
        [self.delegate meterView:self OldValue:oldPos NewValue:newPos];
    }
    else{
        NSLog(@"Delegate call FAIL, needle moved from %f, to %f", oldPos,newPos);
    }
}

-(void)awakeFromNib{

    gauge = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"gauge.png"]];
    needle = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"needle.png"]];
    needle.frame = CGRectMake(0,gauge.frame.size.height-(needle.frame.size.height/2), gauge.frame.size.width, needle.frame.size.height);

    [self addSubview:gauge];
    [self addSubview:needle];
    rotation = 0;
    rgest = [[KTOneFingerRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotate:)];
    rgest.center = CGPointMake(CGRectGetMidX([needle bounds]) + needle.frame.origin.x, CGRectGetMidY([needle bounds]) + needle.frame.origin.y);

    [self addGestureRecognizer:rgest];

}

- (void)rotate:(UIRotationGestureRecognizer *)recognizer {
    switch (recognizer.state) {
        case UIGestureRecognizerStateBegan: {
            oldPos = ([(NSNumber *)[needle.layer valueForKeyPath:@"transform.rotation.z"] floatValue]/3.14)*100;
        }
            break;
        case UIGestureRecognizerStateChanged: {

            CGFloat angle = [(NSNumber *)[needle.layer valueForKeyPath:@"transform.rotation.z"] floatValue];

            angle += [recognizer rotation];
            if (angle >= 0 && angle <= M_PI) {
                [needle setTransform:CGAffineTransformRotate([needle  transform], [recognizer rotation])];
                rotation += [recognizer rotation];
            }

        }
            break;
        case UIGestureRecognizerStateEnded: {
            newPos = ([(NSNumber *)[needle.layer valueForKeyPath:@"transform.rotation.z"] floatValue]/3.14)*100;
            [self handleMovedNeedle];

        }
            break;
        default:
            break;
    }

}

@end

ViewController.h

#import <UIKit/UIKit.h>
#import "MeterView.h"
#import "KTOneFingerRotationGestureRecognizer.h"

@interface ViewController : UIViewController<MeterViewDelegate>{

    IBOutlet MeterView *secondMeter;
    IBOutlet MeterView *thirdMeter;

}

@end

ViewController.m

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>

#define DEG2RAD(degrees) (degrees * 0.01745327) // degrees * pi over 180
#define RAD2DEG(radians) (radians * 57.2957795) // radians * 180 over pi

@interface ViewController ()

@end

@implementation ViewController


- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    secondMeter = [[MeterView alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
    secondMeter.delegate = self;
    thirdMeter = [[MeterView alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
    thirdMeter.delegate =self;
}

-(void)meterView:(MeterView *)view OldValue:(float)oldval NewValue:(float)newval{
    NSLog(@"Delegate call SUCCESS, need moved from %f, to %f", oldval,newval);
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Answer 1

This code:

secondMeter = [[MeterView alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
secondMeter.delegate = self;
thirdMeter = [[MeterView alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
thirdMeter.delegate =self;

creates 2 instances of your view, but it doesn't add them to a view, so they will never be seen.

So, you probably have some other view instances that are on view and don't have delegates, and these views which have delegates but aren't on display. Presumably from an XIB / storyboard as you have outlets.

Connect the views that are on display to the delegate using the outlets rather than creating new instances.

If you make the delegate property in the view an IBOutlet itself then you can connect the view controller as the delegate in the XIB / storyboard and you don't need to worry about the delegate in code at all...