iOS中的动画错误

Question

I'm trying a simple animation by moving a subclass of UIView when a button is pressed. When the button is pressed the view moves xx units away from the original position, the bug is that it comes back to the original position after going xx units away. I want it to stop at the new position. Whats wrong in my code?

[UIView animateWithDuration:0.5f animations:^{
    self.analogStick.frame = CGRectOffset(self.analogStick.frame, 0, -10);
}];

Answer 1

Connect the layout constraints as IBOutlets from Interface Builder into the code. Then in the beginning of the block, set the constraint's constant to the desired value eg setting the left constraint to superview to its constant - 10 .

Then, inside the animation block code, just call [self layoutIfNeeded] . Do not set the frame in any way when you are using constraints (you can use 3D transforms though I personally don't recommend it unless you know exactly what you are doing).