从其他类的方法更改视图的属性

Question

我正在尝试将对象myImageView的alpha远程调整为0 of MyViewController类，从另一个类Assistant(它是NSObject子类)。

在Assistant.h中

#import <Foundation/Foundation.h>

@class MyViewController;

@interface Assistant : NSObject {

    MyViewController *myViewController;
    UIImageView *button;

}
- (void)adjustAlpha:(id)sender;

@property (nonatomic, retain) UIImageView *button;

在Assistant.m中

#import "MyViewController.h"

@implementation Assistant

@synthesize button;

- (id)init 
{
 self = [super init];
 if (self) 
 {
      myViewController = [[MyViewController alloc] init];
      NSLog(@"alloced?: %@", myViewController ? @"YES" : @"NO");
 }
 return self;
}

- (void)adjustAlpha:(id)sender
{
     NSLog(@"method called");
     myViewController.myImageView.alpha = 0;
}

方法确实被调用了，但是myViewController.myImageView.alpha没有改变，为什么？我需要修理的地方？感谢您阅读^_^

编辑

这是MyViewController类：

MyViewController.h

@class Assistant;

@class MyAppAppDelegate;

@interface MyViewController : UIViewController <UITextViewDelegate, UIScrollViewDelegate> 
{
   UIImageView *myImageView;
   Assistant *assistant;
}
@property (nonatomic, retain) UIImageView *myImageView;

MyViewController.m

#import "MyViewController.h"
#import "Assistant.h"

@implementation MyViewController

@synthesize myImageView;


- (void)viewDidLoad 
{
  [super viewDidLoad];
    assistant = [[Assistant alloc] init];
    myScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0,0,320,460);
    [self.view addSubview: myScrollView];


    myImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"weather.png"]];
    myImageView.frame = CGRectMake(19, 54, 48, 48);
    myImageView.userInteractionEnabled = YES;
    [myScrollView addSubview:myImageView];



    //this button uses to call adjustAlpha
    assistant.button = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"button.png"]];  
    assistant.button.frame = CGRectMake(19, 126, 48, 48);
    assistant.button.userInteractionEnabled = YES;
[myScrollView addSubview:assistant.button];

    //here is how i call adjustAlpha:
    assistant.adjustAlphaTap =  [[UITapGestureRecognizer alloc] initWithTarget:assistant action:@selector(adjustAlpha:)];
    [assistant.button addGestureRecognizer:assistant.adjustAlphaTap];

}

这个问题很复杂，需要做一些实验，所以只要挂在上面，我有时间就能弄清楚。对于开发人员来说，遇到了同样的问题:声明您需要在单例类中访问的对象，可以轻松地从任何其他类访问对象，并祝您圣诞快乐！

Answer 1

只有当myImageView声明为MyViewController类的.h文件中的全局作用域变量(也称为iVar)，并且它的属性为(nonatomic, retain)，并在.m中具有匹配的@synthesize时，这才能工作。

如果这听起来像您正在做的事情，那么请您发布您的MyViewController、h和m文件的内容。

Answer 2

如果像托马斯描述的那样定义了所有内容，那么可以检查主线程上是否调用了adjustAlpha方法吗？