UIView 动画发生的速度比指定的秒数快

Question

我有一张图片的视图，其中显示了一些文字。我需要执行逐字显示的动画，最后必须显示完整的文本。

我的界面中有一个徽标视图，上面有一个动画视图。对于动画视图，前导、尾随、顶部和底部约束是基于 superView（徽标视图）设置的。

我尝试了以下代码，但我指定的持续时间无法正常工作。

   - (void) animateLogo {
    [UIView animateWithDuration:10.0 animations:^{
        NSLog(@"animation started");
        if (self.animateViewLeadingConstraint.constant < 94) { //94 is the total width of the logo view
            self.animateViewLeadingConstraint.constant = self.animateViewLeadingConstraint.constant + 1;
        } else {
            self.animateViewLeadingConstraint.constant = 0;
        }
    } completion:^(BOOL finished) {
        NSLog(@"animation ended");
        [self.animateView layoutIfNeeded];
        [self animateLogo];
    }];
}

我已附上持续时间的日志

2016-08-01 17:55:27.317 sample[20361:481531] animation started
2016-08-01 17:55:27.318 sample[20361:481531] animation ended
2016-08-01 17:55:27.318 sample[20361:481531] animation started
2016-08-01 17:55:27.318 sample[20361:481531] animation ended
2016-08-01 17:55:27.318 sample[20361:481531] animation started
2016-08-01 17:55:27.319 sample[20361:481531] animation ended
2016-08-01 17:55:27.319 sample[20361:481531] animation started
2016-08-01 17:55:27.319 sample[20361:481531] animation ended

我不确定我在上面的代码中犯了什么错误，或者我误解了 UIView 动画的概念

如有任何帮助或提示，我们将不胜感激。

Answer 1

看到这个答案：How do I animate constraint changes?

您应该在动画块之前 在动画视图的超级视图上调用 layoutIfNeeded，并在 animations: 块本身中调用。第一次调用确保应用任何布局更改。假设 logoView 是 animateView 的超视图：

- (void) animateLogo { self.animateViewLeadingConstraint.constant = 0.0; [self.logoView layoutIfNeeded]; [UIView animateWithDuration:10.0 animations:^{ NSLog(@"animation started"); self.animateViewLeadingConstraint.constant = 94.0; [self.logoView layoutIfNeeded]; } completion:^(BOOL finished) { NSLog(@"animation ended"); }]; }

Answer 2

最后，我得到了基于@stevekohls 评论的解决方案

- (void) animateLogo {
    self.animateViewLeadingConstraint.constant = 0;
    [UIView animateWithDuration:5.0f animations:^{
        self.animateViewLeadingConstraint.constant = 94.0;
        [self.view layoutIfNeeded];
    } completion:^(BOOL finished) {
        [UIView animateWithDuration:0.5f animations:^{
            self.animateView.alpha = 0;
        } completion:^(BOOL finished) {
                self.animateViewLeadingConstraint.constant = 0;
                [self.view layoutIfNeeded];
                self.animateView.alpha = 1.0f;
                [self animateLogo];
        }];
    }];
}

UIView 动画发生的速度比指定的秒数快

UIView Animation happens faster than specified seconds

objective-c

uiviewanimation

ios