在UITextField中键入按钮不可见时代码不起作用？

Question

这是我在textField中键入任何内容的方法，但是标题按钮在标题中不可见。

- (BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    NSUInteger finalLenght = textField.text.length - range.length + string.length;
    //SearchBtn.hidden = (finalLenght == 0);

    if (finalLenght==0) {
        self.navigationItem.rightBarButtonItem = nil;
    }else{
        UIButton *SearchBtn = [UIButton buttonWithType:UIButtonTypeCustom];
        [SearchBtn setTitle:CustomLocalizedString(@"FIND CVS") forState:UIControlStateNormal];
        [SearchBtn addTarget:self action:@selector(actionFindJobs:) forControlEvents:UIControlEventTouchUpInside];
        SearchBtn.frame = CGRectMake(0, 0, 80, 30);
        SearchBtn.hidden = YES;
        self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:SearchBtn];
    }
    return YES;
}

Answer 1

如何更改此：

SearchBtn.hidden = YES;

至：

SearchBtn.hidden = NO;

Answer 2

请检查以下代码

[SearchBtn setEnabled:YES];

要么

[SearchBtn setEnabled:NO];