//设置初始view的状态toViewController.view.frame = [transitionContext finalFrameForViewController:toViewController];toViewController.view.alpha = 0;toViewController.imageView.hidden = YES;[containerView addSubview:toViewController.view];[containerView addSubview:cellImageSnapshot];

现在我们开始编写view的动画，移动图片的快照、逐渐显示第二个controller的view，在动画结束的block中，移除快照并显示我们之前隐藏了的view，最后，我们需要调用completeTransition:来通知过渡上下文过渡已经完成。

 [UIView animateWithDuration:duration animations:^{toViewController.view.alpha = 1.0;CGRect frame = [containerView convertRect:toViewController.imageView.frame fromView:toViewController.view];cellImageSnapshot.frame = frame;}completion:^(BOOL finished) {toViewController.imageView.hidden = NO;cell.leftImageView.hidden = NO;[cellImageSnapshot removeFromSuperview];[transitionContext completeTransition:!transitionContext.transitionWasCancelled];}];
}

至此，我们运行项目，可以看到从FirstViewController跳转到SecondViewController时，将会看到图片移动的动画效果。

五、Pop动画

不过当我们点击返回时，仍然是系统默认动画。我们只要参照前面push的实现，既首先让SecondViewController遵循UINavigationControllerDelegate协议，实现UINavigationControllerDelegate的方法，并返回一个继承自NSObject、遵循UIViewControllerAnimatedTransitioning协议的实例（Demo中的SecondTransition）。在SecondTransition中实现transitionDuration: 和animateTransition:方法，分别返回过渡的时间、设置动画效果。详见Demo源码。

- (void)handlePopRecognizer:(UIScreenEdgePanGestureRecognizer*)recognizer {// Calculate how far the user has dragged across the viewCGFloat progress = [recognizer translationInView:self.view].x / (self.view.bounds.size.width * 1.0);progress = MIN(1.0, MAX(0.0, progress));if (recognizer.state == UIGestureRecognizerStateBegan) {// Create a interactive transition and pop the view controllerself.interactivePopTransition = [[UIPercentDrivenInteractiveTransition alloc] init];[self.navigationController popViewControllerAnimated:YES];}else if (recognizer.state == UIGestureRecognizerStateChanged) {// Update the interactive transition's progress[self.interactivePopTransition updateInteractiveTransition:progress];}else if (recognizer.state == UIGestureRecognizerStateEnded || recognizer.state == UIGestureRecognizerStateCancelled) {// Finish or cancel the interactive transitionif (progress > 0.5) {[self.interactivePopTransition finishInteractiveTransition];}else {[self.interactivePopTransition cancelInteractiveTransition];}self.interactivePopTransition = nil;}
}


现在我们创建和更新UIPercentDrivenInteractiveTransition实例，我们还需要告诉navigation controller来使用它，在SecondViewController中添加：

- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationControllerinteractionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController {// Check if this is for our custom transitionif ([animationController isKindOfClass:[DSLTransitionFromSecondToFirst class]]) {return self.interactivePopTransition;}else {return nil;}
}