Xcode How to move an image up and down animation - ios

Question

Hey im trying to move an imageview down to the middle of the screen then back up to the top . here is my code , right now it just moves to the middle and stays there .
-(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

I don't like using blocks based animations for chained animations - they tend to grow difficult to read. I would suggest using keyframe animations. This also enables you to easily define a number of intermediary points to your animation, or add more advanced features to your animation, e.g. curves.
Here is an example of how you can animate a UIView linearly between three points.
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;
To do an infinite animation between two points, you could use the code below. Applying it to a UIImageView would work the same.
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

I would propose to use [UIView -animateWithDuration:animations:completion] for that:
[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) {
}];
}];
See Apple Documentation.
Besides that: method names shouldn't start with an uppercase letter