Can I update a label in a UIButton without redrawing the button? - objective-c

Question

I want a clock readout to appear as a label in a UIButton once every second. But even though I remove it from the superView the new UIButton overwrites the old one, like this
… and after several minutes of this my iPhone looked seriously burnt :-)
In PlayViewController my NSTimer methods look like this
- (void)startClock {
clockCount = 0; // start on 1st clock pulse
totalMinutes = 0; // appears on clockButton
totalSeconds = 0; // appears on clockButton
timer = [NSTimer scheduledTimerWithTimeInterval:STATES_ConcertClock
target:self
selector:#selector(nextClock)
userInfo:nil
repeats:YES];
}
- (void)nextClock {
self.lastEventChangeTime = [NSDate date];
clockCount++;
[self masterClockReadout];
}
and here is my clock readout method
- (void)masterClockReadout {
totalMinutes = clockCount / 60;
totalSeconds = clockCount % 60;
clockString = [NSString stringWithFormat:#"%02d:%02d", totalMinutes, totalSeconds];
[self.seconds removeFromSuperview];
EscButton *seconds = [[EscButton alloc] loadEscButton:(NSString *)clockString];
[self.view addSubview:seconds];
}
I also set a UIView property so removeFromSuperview knows what to remove.
#property (nonatomic, retain) UIView* seconds;
My question is: can I update the UIButton label without redrawing the button ? and, is this a problem that might be solved by using a delegate ?
To date my experience using delegates has been for sending messages from the UIButton to ViewController(e.g. below) but so far I haven't found an example I am able to apply where messages are sent in the opposite direction. So if using a delegate is the recommended approach, could you please point me to some code that might help me solve this problem. Thanks
EscButton.h
#import <UIKit/UIKit.h>
#protocol EscButtonDelegate <NSObject>
-(void)fromEscButton:(UIButton*)button;
#end
#interface EscButton : UIView {
}
- (id)loadEscButton:(NSString *)text;
#property (assign) id<EscButtonDelegate> delegate;
#end
EscButton.m
#import "EscButton.h"
#implementation EscButton
- (id)loadEscButton:(NSString *)text {
CGFloat sideOffset = screenWidth - ESC_BUTTON_Width - MARGIN_Side;
CGFloat topOffset = statusBarHeight + MARGIN_Top;
UIButton *escButton = [UIButton buttonWithType:UIButtonTypeCustom];
escButton.frame = CGRectMake(sideOffset, topOffset, ESC_BUTTON_Width, ESC_BUTTON_Height);
// etc …
[escButton addTarget:self.delegate action:#selector(fromEscButton:) forControlEvents:UIControlEventTouchUpInside];
[escButton setTitle:text forState:UIControlStateNormal];
// etc …
return escButton;
}
#end

Answer 1

There is no need to constantly add and remove a button. You can keep the same one. Change the following code:
#property (nonatomic, retain) UIView* seconds;
to:
#property (nonatomic, retain) UIButton *secondsB;
Also change:
[self.seconds removeFromSuperview];
EscButton *seconds = [[EscButton alloc] loadEscButton:(NSString *)clockString];
[self.view addSubview:seconds];
to:
if (!self.secondsB) {
self.secondsB = [[EscButton alloc] loadEscButton:(NSString *)clockString];
[self.view addSubview:_secondsB]; // previously addSubview:seconds];
}
[self.secondsB setTitle:clockString forState:UIControlStateNormal];