NativeScript/tns-core-modules/ui/transition/fade-transition.ios.ts

import { Transition } from "./transition";

export class FadeTransition extends Transition {
    public animateIOSTransition(containerView: UIView, fromView: UIView, toView: UIView, operation: UINavigationControllerOperation, completion: (finished: boolean) => void): void {
        let originalToViewAlpha = toView.alpha;
        let originalFromViewAlpha = fromView.alpha;

        toView.alpha = 0.0;
        fromView.alpha = 1.0;

        switch (operation) {
            case UINavigationControllerOperation.Push:
                containerView.insertSubviewAboveSubview(toView, fromView);
                break;
            case UINavigationControllerOperation.Pop:
                containerView.insertSubviewBelowSubview(toView, fromView);
                break;
        }

        let duration = this.getDuration();
        let curve = this.getCurve();
        UIView.animateWithDurationAnimationsCompletion(duration, () => {
            UIView.setAnimationCurve(curve);
            toView.alpha = 1.0;
            fromView.alpha = 0.0;
        }, (finished: boolean) => {
            toView.alpha = originalToViewAlpha;
            fromView.alpha = originalFromViewAlpha;
            completion(finished);
        });
    }
}