objective-c - 使用 if 语句更改标签文本 - obj c

Question

我有一些 UILabel 和按钮。这是我的代码：

    if ([label.text isEqualToString:@"The three blue dots represents GPS towers. Click Go to advance"])
    {
        firstClick = [[UIAlertView alloc] initWithTitle:@"Welcome!"
                                                message:@"Blah, blah blah"
                                               delegate:self
                                      cancelButtonTitle:@"OK"
                                      otherButtonTitles:nil];
        [firstClick show];

        distanceLabel.text = @"Distance to first tower: 50 km";
        a = YES;
    }

    if (a)
    {
        label.text = @"Now you know that the distance to the first tower is 50 km. Click Go to advance";
    }

所有这些都在按钮的操作方法中。当按下按钮时，alertview 视图和 distanceLabel 更改其文本。然后单击警报上的 OK 按钮我想更改 label.text。我尝试过使用实例布尔值，但这不起作用。为什么那行不通，我该怎么办？

Answer 1

如果您希望在按下警报视图按钮时发生操作，您应该实现协议方法：

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {

    NSLog(@"button clicked at index %d", buttonIndex);
    NSLog(@"about to update a label.  this won't work if it's nil... %@", label);
    label.text = [NSString stringWithFormat:@"user clicked button %d", buttonIndex"];
}