Question

嘿我试图将图像视图向下移动到屏幕中间然后返回到顶部。这是我的代码，现在它只是移动到中间并保持在那里。

-(void)lineGoBack
{
    //move diagonally down
    line.center = CGPointMake(line.center.x,
                              line.center.y-10);
    //start time for first method
    [NSTimer scheduledTimerWithTimeInterval:.5 target:self selector:@selector(LineMovement) userInfo:nil repeats:NO];
}


//The LINE
-(void)LineMovement
{ 
    lineMovementOffset = CGPointMake(line.center.x, screenSizeY/2);

    //move diagonally up
    line.center = CGPointMake(line.center.x,
                              line.center.y+10);

    //start time for second method
    [NSTimer scheduledTimerWithTimeInterval:.5 target:self selector:@selector(lineGoBack) userInfo:nil repeats:NO];
}

Answer 1

我不喜欢将基于块的动画用于链式动画 - 它们往往难以阅读。我建议使用keyframe animations。这使您可以轻松地为动画定义多个中间点，或者为动画添加更多高级功能，例如：曲线。

以下是如何在三点之间线性地设置UIView动画的示例。

CGPoint startPoint = (CGPoint){100.f, 100.f};
CGPoint middlePoint = (CGPoint){400.f, 400.f};
CGPoint endPoint = (CGPoint){600.f, 100.f};

CGMutablePathRef thePath = CGPathCreateMutable();
CGPathMoveToPoint(thePath, NULL, startPoint.x, startPoint.y);
CGPathAddLineToPoint(thePath, NULL, middlePoint.x, middlePoint.y);
CGPathAddLineToPoint(thePath, NULL, endPoint.x, endPoint.y);

CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
animation.duration = 3.f;
animation.path = thePath;
[self.animatedView.layer addAnimation:animation forKey:@"position"];
self.animatedView.layer.position = endPoint;

要在两点之间进行无限动画，可以使用下面的代码。将它应用于UIImageView也可以。

CGPoint startPoint = (CGPoint){100.f, 100.f};
CGPoint endPoint = (CGPoint){400.f, 400.f};

CGMutablePathRef thePath = CGPathCreateMutable();
CGPathMoveToPoint(thePath, NULL, startPoint.x, startPoint.y);
CGPathAddLineToPoint(thePath, NULL, endPoint.x, endPoint.y);

CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
animation.duration = 3.f;
animation.path = thePath;
animation.autoreverses = YES;
animation.repeatCount = INFINITY;
[self.animatedView.layer addAnimation:animation forKey:@"position"];

Answer 2

我建议使用[UIView -animateWithDuration:animations:completion]：

[UIView animateWithDuration:0.5f
                 animations:^{

                     imageView.center = CGPointMake(imageView.center.x, imageView.center.y + 10.0f);

                 } completion:^(BOOL finished) {

                     [UIView animateWithDuration:0.5f
                                      animations:^{

                                          imageView.center = CGPointMake(imageView.center.x, imageView.center.y - 10.0f);

                                      } completion:^(BOOL finished) {

                                      }];
                 }];

请参阅Apple Documentation。

除此之外：方法名称不应以大写字母

开头

Xcode如何上下移动图像动画

2 个答案: