隐藏的XCode 4 UILabel似乎不起作用

Question

I'm having some display trouble wherein I manipulate a UILabel, and even though I use

myLabel.hidden=YES; ...manipulation code... myLabel.hidden=NO;

the label never 'hides' and the manipulation (CATransform3DMakeRotation) is shown (you can see the label flip).

In XCode, I set a breakpoint at the "myLabel.hidden=YES;" line, but as I step through the code, it doesn't hide.

I must be missing something to get the "hidden" method to implement, right? Some kind of refresh or update to the label? Thanks...

Here's the code. "SetStartPosition" is called from several places, not just "doubleTap".

-(void)doubleTap{
    //stop the timer
    [myMover invalidate]; //the timer simply moves the label position
    myMover = nil;
    msgLabel.hidden=YES;
    isMirrored=!isMirrored;
    [self setStartPosition]; //flips the label
    msgLabel.hidden=NO;
    //restart the timer
    [self runMover];
}

- (void)setStartPosition{
    if(isMirrored){
        startPosition=(msgLabel.frame.size.width/2) * -1;
        msgLabel.layer.transform = CATransform3DMakeRotation(M_PI, 0.0f, 1.0f, 0.0f); //M_PI rotates 180 degrees
    }else{
        startPosition=(screenHeight)+(msgLabel.frame.size.width/2);
        msgLabel.layer.transform = CATransform3DMakeRotation(0.0, 0.0f, 1.0f, 0.0f); //0.0 rotate to normal
    }
    newX=startPosition;
    newY=screenWidth/2;
    newFrame = msgLabel.frame;
    newFrame.size.height = screenWidth;
    newFrame.origin.x =newX;
    newFrame.origin.y=newY;
    msgLabel.frame = newFrame;
}

Answer 1

No drawing is done during method execution, it is all done at the next drawing cycle. If your code above is all executed in the same method then the final state of the label will be visible, since you hide and then re-show it before any drawing is done.

If you expand your question to include more context it will be easier to offer a solution.

It looks as if you are getting an animation you don't want because you are modifying an animatable property of a CALayer, giving you an implicit animation. Please see here for guidance on how to override the timing of implicit animations - see "temporarily disabling layer actions"

An alternative is that you are being animated unintentionally because the timer method had queued up a pending change, and your transform is being done at the same time, so it is done in the animation. You should remove any animations from the label before changing the transform.