奇怪的UILabel和UIButton行為

Question

我有一個名為change shape的功能：

- (void)changeShape {

    NSLog(@"**** CHANGE SHAPE ****");

    /* Set previous shape to current shape */
    self.previousShape = self.currentShape;

    /* Transition old shape out of view */
    [UIView animateWithDuration:.4 animations:^(void){
        [self.shapeButton setCenter:CGPointMake(self.view.frame.size.width+200, self.view.frame.size.height/2)];
    } completion:^(BOOL finished){
        if (finished) {

            /* Set new current shape */
            self.currentShape = [NSString stringWithFormat:@"%@",self.shapes[(arc4random() % [self.shapes count])]];
            [self.shapeButton setImage:[UIImage imageNamed:self.currentShape] forState:UIControlStateNormal];

            /* Transition new shape into view */
            [self.shapeButton setCenter:CGPointMake(-200, self.view.frame.size.height/2)];
            [UIView animateWithDuration:.3 animations:^(void){
                [self.shapeButton setCenter:CGPointMake(self.view.frame.size.width/2, self.view.frame.size.height/2)];
            } completion:^(BOOL completed){
                if (completed) {
                    [self changeScore];
                }
            }];
        }
    }];
}

- (void)changeScore {
    self.score++;
    [self.scoreLabel setText:[NSString stringWithFormat:@"%i",self.score]];
}

此功能將UIButton移出屏幕，然后將其動畫化回屏幕。 在最終動畫的結尾，我想增加分數並在屏幕上更改UILabel 。 由於某些原因，只有在更改了UILabel之后，UIButton上的圖像才會更改。 有人知道為什么會這樣嗎？

Answer 1

應用位置更改和新圖像后，調用[self.shapeButton layoutIfNeeded] 。