objective-c - iOS查找 View 是否在设置动画

我正在尝试对UILabel进行动画处理(淡入/淡出)，并且正在使用以下代码:

float newAlpha = 0.0;

//TODO:Check if the previous animation has finished

if(answer.alpha==0.0) {
    newAlpha = 1.0;
} else if(answer.alpha==1.0) {
    newAlpha = 0.0;
}
[UIView animateWithDuration:1.0 animations:^{
    answer.alpha = newAlpha;
}];

在TODO注释所在的位置，我想检查上一个动画是否已完成，如果尚未完成，请退出该方法。有什么办法吗？

最佳答案

更新1:

您需要在 class 中使用一个变量:

BOOL _animationFinished;

然后可以对动画使用以下方式:

float newAlpha = 0.0;

//TODO:Check if the previous animation has finished
if (_animationFinished == false) return;

if(answer.alpha==0.0) {
    newAlpha = 1.0;
} else if(answer.alpha==1.0) {
    newAlpha = 0.0;
}

[UIView animateWithDuration:1.0f animations:^{ answer.alpha = newAlpha; _animationFinished = false; } completion:^(BOOL finished){ _animationFinished = true; }];

它一定是工作。

原始

在这种情况下，我总是检查动画的主题，如下所示:

float newAlpha = 0.0;

//TODO:Check if the previous animation has finished
if (answer.alpha > 0.f || answer.alpha < 1.f) return; // it is always good enough for me
// ...or with AND it will cause the same effect:
// if (answer.alpha > 0.f && answer.alpha < 1.f) return;

if(answer.alpha==0.0) {
    newAlpha = 1.0;
} else if(answer.alpha==1.0) {
    newAlpha = 0.0;
}
[UIView animateWithDuration:1.0 animations:^{
    answer.alpha = newAlpha;
}];