/**
隐藏 返回键 的做法，将title置为空
*/
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithTitle:@" " style:UIBarButtonItemStylePlain target:nil action:nil];
//收起键盘
-(void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
[self.textView endEditing:YES];
}
-(BOOL)textFieldShouldReturn:(UITextField *)textField{
return self.textView.resignFirstResponder;
}