objective-c - UITextField 边框动画

Question

我正在尝试为 UITextField 边框颜色设置动画(淡入)。这是我的尝试

tmp.layer.borderColor= [UIColor colorWithRed:255.0 green:0.0 blue:0.0 alpha:0.0].CGColor;
tmp.layer.borderWidth = 1.0f;

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:2];
tmp.layer.borderColor= [UIColor colorWithRed:255.0 green:0.0 blue:0.0 alpha:1.0].CGColor;
[UIView commitAnimations];

上面的代码向文本字段添加了红色边框，但没有动画。

Answer 1

我在为 UITextField 的边框设置动画时遇到了麻烦，所以我想提供我的解决方案。我能够使用 CABasicAnimation 执行 UITextField 动画来完成我的任务。

下面是代码块:

textField.layer.borderWidth = 1.0f;

[CATransaction begin]; {
    [CATransaction setCompletionBlock:^{
        // How the textField should look at the end of the animation.
        textField.layer.borderColor = [UIColor colorWithRed:255.0 green:0.0 blue:0.0 alpha:1.0].CGColor;

    }];

    // The keyPath specifies which attribute to modify. In this case it's the layer's borderColor.
    CABasicAnimation *colorAnimation = [CABasicAnimation animationWithKeyPath:@"borderColor"];

    // fromValue provides the beginning state of the animation.
    colorAnimation.fromValue = (__bridge id)[UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.0].CGColor;

    // The to value is the final state of the animation. NOTE: That upon completion of the animation is removed.
    colorAnimation.toValue   = (__bridge id)[UIColor colorWithRed:255.0 green:0.0 blue:0.0 alpha:1.0].CGColor ;
    color.duration = 2.0;

    // Finally you add the animation to the textField's layer.
    [textField.layer addAnimation:colorAnimation forKey:@"color"];

} [CATransaction commit];

现在动画只是一个临时叠加在现有动画之上的图层。所以为了让动画的最终结果永久存在有两种方法:

1. 您可以将最终结果设置到 CATransaction 完成 block 中的 UITextField 层。如上面的代码所示。

2. 通过将动画的接收器设置为在其最终状态下可见并防止移除动画。如下所示:

       // Prevents the removal of the final animation state from visibility. 
       // Add these before you add the animation to the textField's layer.
       colorAnimation.fillMode = kCAFillModeForwards;
       colorAnimation.removedOnCompletion = false;