Question

我正在创建一个应用程序，当用户按下按钮时，在UILabel中显示一个随机单词（NSDictionary中的一个键）和另一个UILabel中的相关单词列表（NSArray，即显示键的值）。例如：如果用户按下按钮，主要单词可能是“Cat”，列表可能是“lion”，“snow leopard”，“tiger”。

我想循环文本输出，以便用户按下按钮一次，得到一个单词和一个列表，有一个定时暂停，然后单词和列表刷新。这是我到目前为止的方法：

- (IBAction)changeWord:(UIButton*)sender {
        //next line displays the randomly selected NSDictionary key, such as "Cat" in a label
        self.label.text = [self.dictionary selectKey];
        //next two lines displays the value associated with the selected key (an array), such as "lion", "snow leopard", "tiger" in another label
        NSString *labelText = [[NSString alloc] initWithFormat:@"%@", [self.dictionary selectList]];
        self.listLabel.text = labelText;
       }

这显然不会循环，只需按下按钮就会显示两个标签的新输出。我认为创建一个循环，循环次数与字典键一样多，可以解决问题的一半：

- (IBAction)changeWord:(UIButton*)sender {

    //next line counts the keys in the NSDictionary
    NSInteger numberOfKeys = [self.dictionary CountKeys];
   for( int index = 0; index < numberOfKeys; index++ ) 
   {
    self.label.text = [self.dictionary selectKey];
    NSString *labelText = [[NSString alloc] initWithFormat:@"%@", [self.dictionary selectList]];
    self.listLabel.text = labelText;
   //need some type of timer here! 
   }

但我需要某种类型的计时器，它会在刷新之前定期暂停显示。那就是我被困住的地方！

有没有人有任何指示？

非常感谢！

Answer 1

您可以使用NSObject的方法performSelector:withObject:afterDelay\]：

- (IBAction)changeWord:(UIButton*)sender
{
    [self changeWord];
}

- (void)changeWord
{
    if (musicStopped) return;

    //next line displays the randomly selected NSDictionary key, such as "Cat" in a label
    self.label.text = [self.dictionary selectKey];
    //next two lines displays the value associated with the selected key (an array), such as "lion", "snow leopard", "tiger" in another label
    NSString *labelText = [[NSString alloc] initWithFormat:@"%@", [self.dictionary selectList]];
    self.listLabel.text = labelText;

    // Add this line
    [self performSelector:@selector(changeWord) withObject:nil afterDelay:30.0];
}

在iPhone上定时循环文本输出

1 个答案: