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首先遵循UIGestureRecognizerDelegate协议
self.navigationController.interactivePopGestureRecognizer.enabled = YES;
self.navigationController.interactivePopGestureRecognizer.delegate = self;
ios系统自带的左化返回上一级页面
原文地址：http://www.cnblogs.com/xiaolingling1126/p/5083052.html
