這個(gè)方法用在返回按鈕是自定義的時(shí)候
UIView *emptyView = [[UIView alloc] init];;
UIBarButtonItem *emptyButton = [[UIBarButtonItem alloc] initWithCustomView:emptyView];
[self.navigationItem setLeftBarButtonItem:emptyButton animated:YES];
```
## 這個(gè)方法只有在返回按鈕是系統(tǒng)的時(shí)候才有效果
[self.navigationItem setHidesBackButton:YES animated:YES];
