仿新浪微博 UINavigationController 向左滑动时显示上一个控制器的View.
实现原理,UINavigationController 的 self.view显示时把当前显示的view截图下来，，保存到一个数组中。当push一个view时把上一个view的截图放到self.view后面,当self.view向右拖动时显示上一个view。
NavigationController.m
#import "NavigationController.h"@interface NavigationController ()/** 存放每一个控制器的全屏截图 */@property (nonatomic, strong) NSMutableArray *images;@property (nonatomic, strong) UIImageView *lastVcView;@property (nonatomic, strong) UIView *cover;@end@implementation NavigationController- (UIImageView *)lastVcView{if (!_lastVcView) {UIWindow *window = [UIApplication sharedApplication].keyWindow;UIImageView *lastVcView = [[UIImageView alloc] init];lastVcView.frame = window.bounds;self.lastVcView = lastVcView;}return _lastVcView;}- (UIView *)cover{if (!_cover) {UIWindow *window = [UIApplication sharedApplication].keyWindow;UIView *cover = [[UIView alloc] init];cover.backgroundColor = [UIColor blackColor];cover.frame = window.bounds;cover.alpha = 0.5;self.cover = cover;}return _cover;}- (NSMutableArray *)images{if (!_images) {self.images = [[NSMutableArray alloc] init];}return _images;}- (void)viewDidLoad {[super viewDidLoad];// 拖拽手势UIPanGestureRecognizer *recognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(dragging:)];[self.view addGestureRecognizer:recognizer];}- (void)dragging:(UIPanGestureRecognizer *)recognizer{// 如果只有1个子控制器,停止拖拽if (self.viewControllers.count <= 1) return;// 在x方向上移动的距离CGFloat tx = [recognizer translationInView:self.view].x;if (tx < 0) return;if (recognizer.state == UIGestureRecognizerStateEnded || recognizer.state == UIGestureRecognizerStateCancelled) {// 决定pop还是还原CGFloat x = self.view.frame.origin.x;if (x >= self.view.frame.size.width * 0.5) {[UIView animateWithDuration:0.25 animations:^{self.view.transform = CGAffineTransformMakeTranslation(self.view.frame.size.width, 0);} completion:^(BOOL finished) {[self popViewControllerAnimated:NO];[self.lastVcView removeFromSuperview];[self.cover removeFromSuperview];self.view.transform = CGAffineTransformIdentity;[self.images removeLastObject];}];} else {[UIView animateWithDuration:0.25 animations:^{self.view.transform = CGAffineTransformIdentity;}];}} else {// 移动viewself.view.transform = CGAffineTransformMakeTranslation(tx, 0);UIWindow *window = [UIApplication sharedApplication].keyWindow;// 添加截图到最后面self.lastVcView.image = self.images[self.images.count – 2];[window insertSubview:self.lastVcView atIndex:0];[window insertSubview:self.cover aboveSubview:self.lastVcView];}}/** * 产生截图 */- (void)createScreenShot{UIGraphicsBeginImageContextWithOptions(self.view.frame.size, YES, 0.0);[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];UIImage *image = UIGraphicsGetImageFromCurrentImageContext();[self.images addObject:image];}- (void)viewDidAppear:(BOOL)animated{[super viewDidAppear:animated];if (self.images.count > 0) return;[self createScreenShot];}- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated{[super pushViewController:viewController animated:animated];[self createScreenShot];}@end
每一个成功者都有一个开始。勇于开始，才能找到成功的路。
