2016.11.23添加自定义导航栏左按钮

按照某些教程操作后按钮不显示，添加[self.view addSubview:backBtn]后就可显示了。

- (void)viewDidLoad {

   

    [superviewDidLoad];

    UIButton *backBtn = [UIButtonbuttonWithType:UIButtonTypeCustom];

    backBtn.frame =CGRectMake(10,30, 40,20);

    

    [backBtn setImage:[UIImageimageNamed:@"back.png"]forState:UIControlStateNormal];

    [backBtn addTarget:selfaction:@selector(doBack:)forControlEvents:UIControlEventTouchUpInside];

    

    [self.viewaddSubview:backBtn];

    // Do any additional setup after loading the view.

}