Question

我是xcode的初学者。如何为尚未完成的内容编写代码，在UILabel（labelDate）中写入信息或没有值，然后使用UIAlertView弹出窗口告诉您是否还没有输入信息？

我的UILabel从下面的代码中获取输入

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    year = [picker selectedRowInComponent:0];
    month = [picker selectedRowInComponent:1];
    day = [picker selectedRowInComponent:2];
    date = @"";
    if(viewPicker.tag == 1)
        labelDate.text = [date stringByAppendingFormat:@"%d:%d:%d", year , month, day];
    else
    ... etc
}

我的按钮就像这样

- (IBAction)readyBtn:(id)sender { 
    if ( ??? ) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Please input date" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
    }

我已经尝试过像这样编写，但我认为这不是一个好主意，因为如果年，月，日被选为0，则uialertview会弹出。

- (IBAction)readyBtn:(id)sender { 
    if (viewPicker.tag == 1) {
        year = month = day = 0;
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Please input date" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
    }

谢谢你教我。

Answer 1

如果您想检查您的UILabel是否没有值，请在您的函数中执行以下操作

- (IBAction)readyBtn:(id)sender { 
    if ( [yourLabel.text isEqualToString:@""]) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Please input date" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
    }

Answer 2

检查输入的日期是否为零，如果为零，则弹出警报视图。或

if(entereddate.text isEqualToString:" ")
{
       UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Please input date" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
            [alert show];

}

Answer 3

你的Button事件将是这样的：

 - (IBAction)readyBtn:(id)sender 
 { 
    if ( labelDate.text.length >0 ) // Add OR condition for any other lablel or textField
    {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:@"Please input date" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    }
}

我应该为“无价值”陈述写什么？

3 个答案: