手势控制页面转换与实现-CSDN博客

本文链接：https://blog.csdn.net/shidongdong2012/article/details/47005987

接上篇文章，相信大家实现简单的Push已经不再话下了把,那么上一篇是入门，这一篇将继续介绍如何实现手势返回。

我们需要实现最重要的交互过程的类：

UIPercentDrivenInteractiveTransition

这里面的方法相信大家已经知道，最重要的3个方法：

- (void)updateInteractiveTransition:(CGFloat)percentComplete;
- (void)cancelInteractiveTransition;
- (void)finishInteractiveTransition;

我们通过手势控制，然后通过手势去更新我们的交互过程，主要就是依靠以上方法去更新我们的交互过程。

首先，我们简单一点，先写一个Pop的动画，直接附上源码：

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext
{
    return 0.2;
}

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
    CGRect screenBounds = [[UIScreen mainScreen] bounds];
    UIViewController * fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController * toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    
    CGRect initFrame = [transitionContext initialFrameForViewController:fromVC];
    CGRect finalFrame  = CGRectOffset(initFrame, screenBounds.size.width , 0);
    
    UIView *containerView = [transitionContext containerView];
    [containerView addSubview:toVC.view];
    [containerView sendSubviewToBack:toVC.view];
    
    NSTimeInterval duration = [self transitionDuration:transitionContext];
    [UIView animateWithDuration:duration animations:^{
        //fromVC.view.alpha = 0.0;
        fromVC.view.transform = CGAffineTransformMakeScale(1.0, 0.0001);
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    }];
    
}

和Push进来的动画差不多，但是注意

  UIView *containerView = [transitionContext containerView];
    [containerView addSubview:toVC.view];
    [containerView sendSubviewToBack:toVC.view];

这几句非常关键，我们在实现页面转换的时候，需要一个容器进行动画转场，而系统就替我们创建了一个转场的View，需要注意，如果不加上这句话，我们的转场动画会突然黑一下，因为我们的ToviewController.View没有添加在容器内，容器内空空如也，所以直接就是黑色，如果加了这个，等于我们有了个背景一样，就比较好流畅了。

Pop的动画实现了，我们怎么实现手势控制呢？

- (id <UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id <UIViewControllerAnimatedTransitioning>)animator

还记得这个吗，就是我们一开始transitioningDelegate

这个是负责交互控制，如果动画是交互的动画实现，那么这个就是控制动画的，注意上面的

UIPercentDrivenInteractiveTransition

也是遵循

UIViewControllerInteractiveTransitioning

所以我们完全可以实现一个负责交互控制的类。

- (void)prepareForController:(UIViewController *)controller
{
    self.presentViewController = controller;
    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleGesture:)];
    [controller.view addGestureRecognizer:gesture];
    
}

-(CGFloat)completionSpeed
{
    return 1 - self.percentComplete;
}


- (void)handleGesture:(UIPanGestureRecognizer *)gestureRecognizer {
    
    CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view.superview];
    switch (gestureRecognizer.state) {
        case UIGestureRecognizerStateBegan:
            // 1. Mark the interacting flag. Used when supplying it in delegate.
            self.interacting = YES;
            [self.presentViewController dismissViewControllerAnimated:YES completion:nil];
            break;
        case UIGestureRecognizerStateChanged: {
            // 2. Calculate the percentage of guesture
            NSLog(@"........%f",translation.y);
            CGFloat fraction = translation.y / 400.0;
            //Limit it between 0 and 1
            fraction = fminf(fmaxf(fraction, 0.0), 1.0);
            self.shouldComplete = (fraction > 0.5);
            
            [self updateInteractiveTransition:fraction];
            break;
        }
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled: {
            // 3. Gesture over. Check if the transition should happen or not
            self.interacting = NO;
            if (!self.shouldComplete || gestureRecognizer.state == UIGestureRecognizerStateCancelled) {
                [self cancelInteractiveTransition];
            } else {
                [self finishInteractiveTransition];
            }
            break;
        }
        default:
            break;
    }
    
    
}

我们通过手势，去更新交互，取消交互或者完成交互，这样就完成了，我们从第一篇，讲如何push到一个页面，如何Pop，如何手势Pop。

还有一点需要注意，手势的更新，取消，只是让我们去控制Pop的动画。

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