自定义过渡将UIViewController扩展到左侧

Question

I am trying to create a custom animation to present a new view controller into display. The from view controller is a view controller that has two embed uiviewcontrollers The one on the right is a view controller enclosed in a navigation controller and the first half of the animation that I am attempting is to make the right container expand to the left going full screen.

When I perform the standard UIView animation block setting its frame = its parent frame it first sets the size immediately (ignoring the animation) by expanding to the right, and then centers itself.

Basically my question is does anyone have a suggestion on how to force the view controller to expand strictly to the left direction at the proper speed ? Scale doesn't work to my knowledge as it stretches the view not preserving aspect ratio.

Answer 1

This can be done by animating the size or position of the container views. In a test, I set up the container views such that the left one had a width constraint (IBOutlet, widthCon), and the right container had a 0 length spacing constraint to the left container. Expanding was done with this code in the parent view controller,

- (void)expandRightView {

    [UIView animateWithDuration:2 animations:^{
        self.widthCon.constant = 0;
        [self.view layoutIfNeeded];
    }];
}

It can also be done by moving the left container to the left instead (leftCon is the IBOutlet to the constraint between the left container view and the left edge of the main view),

- (void)expandRightView {

    [UIView animateWithDuration:2 animations:^{
        self.leftCon.constant = -self.leftContainerView.frame.size.width;
        [self.view layoutIfNeeded];
    }];
}