首先貼上sunnyxx大神的博客 一個絲滑的全屏滑動返回手勢

FDFullscreenPopGesture是通過替換系統(tǒng)原生的右滑返回手勢來實現(xiàn)全屏滑動返回的效果

手勢返回

為了實現(xiàn)對原有項目0侵入性，那么就需要hook原有方法來實現(xiàn)

+ (void)load
{
    // Inject "-pushViewController:animated:"
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];
        
        SEL originalSelector = @selector(pushViewController:animated:);
        SEL swizzledSelector = @selector(fd_pushViewController:animated:);
        
        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
        
        BOOL success = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
        if (success) {
            class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

hook這種也不需要詳解了，谷歌一下也有很多解釋了，最主要的還是要看被hook的fd_pushViewController:animated:方法

- (void)fd_pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (![self.interactivePopGestureRecognizer.view.gestureRecognizers containsObject:self.fd_fullscreenPopGestureRecognizer]) {
        
        // Add our own gesture recognizer to where the onboard screen edge pan gesture recognizer is attached to.
        [self.interactivePopGestureRecognizer.view addGestureRecognizer:self.fd_fullscreenPopGestureRecognizer];
        
        // Forward the gesture events to the private handler of the onboard gesture recognizer.
        NSArray *internalTargets = [self.interactivePopGestureRecognizer valueForKey:@"targets"];
        id internalTarget = [internalTargets.firstObject valueForKey:@"target"];
        SEL internalAction = NSSelectorFromString(@"handleNavigationTransition:");
        self.fd_fullscreenPopGestureRecognizer.delegate = self.fd_popGestureRecognizerDelegate;
        [self.fd_fullscreenPopGestureRecognizer addTarget:internalTarget action:internalAction];
        
        // Disable the onboard gesture recognizer.
        self.interactivePopGestureRecognizer.enabled = NO;
    }
    
    // Handle perferred navigation bar appearance.
    [self fd_setupViewControllerBasedNavigationBarAppearanceIfNeeded:viewController];
    
    // Forward to primary implementation.
    if (![self.viewControllers containsObject:viewController]) {
        [self fd_pushViewController:viewController animated:animated];
    }
}

第一步的做法是用自己創(chuàng)建的手勢來替換掉系統(tǒng)原生的返回手勢以實現(xiàn)全屏返回手勢

為什么自己創(chuàng)建的fd_fullscreenPopGestureRecognizer的target&action要設(shè)為系統(tǒng)默認的target&action呢？因為UINavigationController導航控制器的pop&push的層級關(guān)系是由系統(tǒng)管理的(參考[J_雨])。所以只需要決定fd_fullscreenPopGestureRecognizer是否能響應(yīng)就行了

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)gestureRecognizer
{
    // Ignore when no view controller is pushed into the navigation stack.
    if (self.navigationController.viewControllers.count <= 1) {
        return NO;
    }
    
    // Ignore when the active view controller doesn't allow interactive pop.
    UIViewController *topViewController = self.navigationController.viewControllers.lastObject;
    if (topViewController.fd_interactivePopDisabled) {
        return NO;
    }
    
    // Ignore when the beginning location is beyond max allowed initial distance to left edge.
    CGPoint beginningLocation = [gestureRecognizer locationInView:gestureRecognizer.view];
    CGFloat maxAllowedInitialDistance = topViewController.fd_interactivePopMaxAllowedInitialDistanceToLeftEdge;
    if (maxAllowedInitialDistance > 0 && beginningLocation.x > maxAllowedInitialDistance) {
        return NO;
    }

    // Ignore pan gesture when the navigation controller is currently in transition.
    if ([[self.navigationController valueForKey:@"_isTransitioning"] boolValue]) {
        return NO;
    }
    
    // Prevent calling the handler when the gesture begins in an opposite direction.
    CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view];
    BOOL isLeftToRight = [UIApplication sharedApplication].userInterfaceLayoutDirection == UIUserInterfaceLayoutDirectionLeftToRight;
    CGFloat multiplier = isLeftToRight ? 1 : - 1;
    if ((translation.x * multiplier) <= 0) {
        return NO;
    }
    
    return YES;
}

當為以下情況的時候，全屏返回手勢不生效:

• 導航棧沒有push視圖控制器，也就是說導航棧只有根視圖或則沒有視圖的時候不生效
• 當前導航棧的棧頂視圖控制器不允許全屏返回
• 手勢開始的點小于設(shè)置的最大允許距離
• 當前正在進行過渡態(tài)動畫
• 當前手勢不是從左往后滑

導航欄的顯示隱藏

- (void)fd_setupViewControllerBasedNavigationBarAppearanceIfNeeded:(UIViewController *)appearingViewController
{
    if (!self.fd_viewControllerBasedNavigationBarAppearanceEnabled) {
        return;
    }
    
    __weak typeof(self) weakSelf = self;
    _FDViewControllerWillAppearInjectBlock block = ^(UIViewController *viewController, BOOL animated) {
        __strong typeof(weakSelf) strongSelf = weakSelf;
        if (strongSelf) {
            [strongSelf setNavigationBarHidden:viewController.fd_prefersNavigationBarHidden animated:animated];
        }
    };
    
    // Setup will appear inject block to appearing view controller.
    // Setup disappearing view controller as well, because not every view controller is added into
    // stack by pushing, maybe by "-setViewControllers:".
    appearingViewController.fd_willAppearInjectBlock = block;
    UIViewController *disappearingViewController = self.viewControllers.lastObject;
    if (disappearingViewController && !disappearingViewController.fd_willAppearInjectBlock) {
        disappearingViewController.fd_willAppearInjectBlock = block;
    }
}

每次push一個新的視圖控制器的時候，都會設(shè)置一個_FDViewControllerWillAppearInjectBlock，用于在視圖即將顯示的設(shè)置導航欄的顯示與隱藏，因此我們只需要簡單的設(shè)置fd_prefersNavigationBarHidden屬性，試圖控制器每次在即將顯示viewWillAppear:的時候設(shè)置導航欄是否隱藏就行了。

疑問

- (void)fd_viewWillDisappear:(BOOL)animated
{
    // Forward to primary implementation.
    [self fd_viewWillDisappear:animated];
    
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        UIViewController *viewController = self.navigationController.viewControllers.lastObject;
        if (viewController && !viewController.fd_prefersNavigationBarHidden) {
            [self.navigationController setNavigationBarHidden:NO animated:NO];
        }
    });
}

對于這里，我不是很明白為什么在試圖控制器即將消失的時候，為什么還要設(shè)置導航欄隱藏呢？如果是pop的話，viewController為nil，但如果是push的話，不是已經(jīng)在viewWillAppear:的時候設(shè)置了導航了嗎？

個人感覺是最后避免想顯示導航欄卻沒顯示的不就措施吧？

希望有懂的大神能告訴我一下，私聊我也行，??評論區(qū)講解一下也想，當然有不同的想法的也可以在??評論區(qū)發(fā)表意見