[ios]制作一个backBraButton

  UIButton* backButton = [UIButton buttonWithType:101]; // left-pointing shape!

        [backButton setTitle:@"更多" forState:UIControlStateNormal];

        [backButton addTarget:self action:@selector(btBackPressed:) forControlEvents:UIControlEventTouchUpInside];

        UIBarButtonItem* tempBar=[[UIBarButtonItem alloc]initWithCustomView:backButton];

        self.navigationItem.leftBarButtonItem=tempBar;