CABasicAnimation位置。Y

Question

我只想用这个函数来动画我的UIButton的位置：

CABasicAnimation *moveUp;
    moveUp          = [CABasicAnimation animationWithKeyPath:@"position.y"];
    moveUp.fromValue = [NSNumber numberWithFloat:self.retestBTN.frame.origin.y];
    moveUp.toValue  = [NSNumber numberWithFloat:self.retestBTN.frame.origin.y - 50];
    moveUp.duration = 1.0;
    moveUp.removedOnCompletion = NO;
    moveUp.fillMode = kCAFillModeBoth;
    moveUp.delegate = self;
    [[retestBTN layer] addAnimation:moveUp forKey:@"y"];

然后我想稍后用这个函数重新设置它的动画：

CABasicAnimation *moveDown;
moveDown            = [CABasicAnimation animationWithKeyPath:@"position.y"];
moveDown.fromValue  = [NSNumber numberWithFloat:self.retestBTN.frame.origin.y];
moveDown.toValue    = [NSNumber numberWithFloat:self.retestBTN.frame.origin.y + 50];
moveDown.duration   = 1.0;
moveDown.removedOnCompletion = NO;
moveDown.fillMode   = kCAFillModeForwards;
[[retestBTN layer] addAnimation:moveDown forKey:@"y"];

但这不能正常工作，我的UIButton转到了奇怪的位置...

Answer 1

通过使用CAAnimation，您只能为层设置动画。实际上，您不会更改对象的modelLayer，只会更改presentationLayer，因为您只会创建动画，而不会实际更改图层的position属性。这意味着按钮不会实际移动，而只是在屏幕上绘制的位置移动。

如果你的按钮是一个UIButton，那么它仍然会在视图所在的地方接受触摸，而不是在图层所在的地方。使用UIKit可以更轻松地为任何视图设置动画，如下所示：

[UIView animateWithDuration:1.0
                      delay:0.0
                    options:UIViewAnimationOptionCurveEaseInOut
                 animations:^{
                     CGRect frame = self.retestBTN.frame;
                     frame.origin.y -= 50;
                     self.retestBTN.frame = frame;
                 }
                 completion:^(BOOL finished){
                     //callback code goes here
                 }];

Answer 2

您面临的问题是位置与原点不同。

无论如何，您正在制作位置的相对动画，因此如果您跳过toValue和fromValue，而使用byValue属性(具有相对更改)，将会更容易。您的代码将如下所示：

CABasicAnimation *moveUp;
moveUp          = [CABasicAnimation animationWithKeyPath:@"position.y"];      
moveUp.byValue  = @(-50.0f); // or [NSNumber numberWithFloat:-50.0f] if you really need to
moveUp.duration = 1.0;
moveUp.removedOnCompletion = NO;
moveUp.fillMode = kCAFillModeBoth;
moveUp.delegate = self;
[[retestBTN layer] addAnimation:moveUp forKey:@"y"];

和

CABasicAnimation *moveDown;
moveDown            = [CABasicAnimation animationWithKeyPath:@"position.y"];
moveDown.byValue    = @(50.0f); // or [NSNumber numberWithFloat:50.0f] if you really need to
moveDown.duration   = 1.0;
moveDown.removedOnCompletion = NO;
moveDown.fillMode   = kCAFillModeForwards;
[[retestBTN layer] addAnimation:moveDown forKey:@"y"];