定位以编程方式创建的UIButton

Question

Question: How do I target one of many dynamically created UIButtons so I can change its properties?

Background: I have a storyboard with a UIViewConroller. When this UIVC loads a UIScrollView is added, to which a UIImageView is placed that has an exhibition floor plan. Each exhibitor has an entry in a database that contains its location on the floor plan. When the UIVC is loaded a loop is run for all exhibitors and each one has a UIButton drawn on the UIIV. When a UIB is clicked the button background colour is changed (to confirm which exhibitor has been selected) and a UIAlertView is shown with information about that exhibitor. When the UIAV's 'cancel' (ok) button is pressed the UIAV closes and the background highlight colour that was applied previously should be removed but here is where I am having the problem. I am unable to target the UIButton so I can change its background colour.

What I have tried so far: As each button is created I am giving it a tag and a title and recording both in an array. When the 'cancel' button is pressed on the UIAlertView I have tried checking the tag in the array but I still cannot actually target the UIButton.

I was thinking something like this:

// obviously not correct syntax but the kind of thing I want
[exhibitorBtn(tag) setBackgroundColor:[UIColor greenColor]];

So, say I have 12 UIButtons all called exhibitorBtn but with different titles and tags:

• Object ----- Name ---------- Title -------- Tag

• UIButton -- exhibitorBtn -- Glaxo ------ 1

• UIButton -- exhibitorBtn -- Porsche --- 2

• UIButton -- exhibitorBtn -- Rolex ------- 3 < How would I target that button's properties?

Edit - added the code that creates the buttons just to clarify:

 for (NSDictionary *dict in exhibitorStandArray) {

    NSInteger currentPosition = [exhibitorStandArray indexOfObject:dict];
    NSLog(@"Position in array = %li", (long)currentPosition);
    if (![dict[@"locCoords"] isEqual: @""]) {

        NSInteger buttonTag = [exhibitorStandArray indexOfObject:dict];
        NSString *standNo = dict[@"locStandNo"];
        NSMutableDictionary *buttonDictionary = [[NSMutableDictionary alloc] init];
        [buttonDictionary setObject:[NSNumber numberWithInteger:buttonTag] forKey:@"buttonTag"];
        [buttonDictionary setObject:standNo forKey:@"buttonStandNo"];

        [_masterButtonList addObject:buttonDictionary];

        NSString *locCoords = dict[@"locCoords"];
        NSArray *tempArray =[locCoords componentsSeparatedByString:@","];
        tlcTop = [[tempArray objectAtIndex:0] integerValue];
        tlcLeft = [[tempArray objectAtIndex:1] integerValue];
        brcTop = [[tempArray objectAtIndex:2] integerValue];
        brcRight = [[tempArray objectAtIndex:3] integerValue];
        buttonWidth = brcRight - tlcLeft;
        buttonHeight = brcTop - tlcTop;

        testBtn = [UIButton buttonWithType:UIButtonTypeCustom];
        testBtn.frame = CGRectMake(tlcTop, tlcLeft, buttonHeight, buttonWidth);
        testBtn.titleLabel.text = standNo;
        testBtn.tag = buttonTag;
        NSLog(@"UIButton Title = %@", testBtn.titleLabel.text);
        NSLog(@"UIButton Tag = %li", (long)testBtn.tag);

        testBtn.titleLabel.hidden = YES;

        [testBtn addTarget:self action:@selector(displayInfo:) forControlEvents:UIControlEventTouchUpInside];

        [_buttonArray addObject:testBtn];
        [_imageView addSubview:testBtn];
     }   
}

Answer 1

为什么不能只使用viewWithTag:

    UIButton * button = (UIButton *)[self.scrollView viewWithTag:tag];

Answer 2

Your code probably looks something like this:

for (int i = 0; i < 5; i++)
{
    UIButton *exhibitorBtn = [[UIButton alloc] initWithFrame:etc..];
    exhibitorButton.tag = i;
    [scrollView addSubview:exhibitorBtn];
}

Just change the loop so every button will be added to an array, too. Declare a NSMutableArray as a property: @property (strong, nonatomic) NSMutableArray *buttonsArray;

And @synthesize and initialise it in your init method. buttonsArray = [[NSMutableArray alloc] init]

Then, change the loop like I said above:

for (int i = 0; i < 5; i++)
{
    UIButton *exhibitorBtn = [[UIButton alloc] initWithFrame:etc..];
    exhibitorButton.tag = i;
    [buttonsArray addObject:exhibitorBtn];
    [scrollView addSubview:exhibitorBtn];
}

Finally, when you want to access the buttons:

for (int i = 0; i < [buttonsArray count]; i++)
{
    UIButton *button = [buttonsArray objectAtIndex:i];

    if (button.tag == 3) { // This is the button you wanted to target!
        [button setHidden:YES];
    }
}

Answer 3

Let's make it clear: you did set target and action of UIButton to controller's IBAction method and get the button as sender argument. Now you show UIAlertView and after it is dismissed, you want to send some message to that button, right?

Another method is to set delegate property for UIAlertView and respond to – alertView:clickedButtonAtIndex: delegate method. Trouble is that sender is lost at that point. You may use objc_setAssociatedObject to associate UIButton with UIAlertView and the retrieve it back when delegate method fires:

#import <objc/runtime.h>
static char myButtonKey = 0; // to use address as a key (value is irrelevant)

- (IBAction)buttonDidClick:(id)button
{
    UIAlertView *alertView = <setup alert>;
    [alertView setDelegate:self];
    objc_setAssociatedObject(alertView, &myButtonKey, button, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    <show alert>;
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    UIButton *thatButton = objc_getAssociatedObject(alertView, &myButtonKey);
    <use thatButton>;
}

Answer 4

Try to create button in this way and add selector to them :

for (int i = 0; i < 5; i++)
{
    UIButton *button = [[UIButton alloc] initWithFrame:CGRectZero];

    button.tag = i;
    [button addTarget:self
               action:@selector(buttonPressedMethod:)
     forControlEvents:UIControlEventTouchDown];
    [button setTitle:@"Show View" forState:UIControlStateNormal];

    // add button to subview here
}

In method, just do whatever, you want to do :

- (void) buttonPressedMethod : (id) sender {
UIButton *selectedButton = (UIButton *)sender;

  if (selectedButton.tag == 0) {

  }

  else if (selectedButton.tag == 1) {

  }


  else {

  }

}