创建一个随时间递增的标签，iOS答案

【问题标题】：Creating a label that counts up over time, iOS创建一个随时间递增的标签，iOS
【发布时间】：2015-05-18 05:21:38
【问题描述】：

我正在尝试创建一个标签（或任何 UI 元素），它从一个数字开始并向上计数，同时不会减慢所有其他进程。

我不完全确定如何使用多线程/GCD/NSTimer 来使其与 iOS 一起工作是最好的。有什么建议？这是我目前拥有的代码：

    -(void)countup:(UIBarButtonItem *)label from:(int)startNumber to:(int)endNumber{
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    //         double timeInterval = 5; //5 seconds from start to stop
    //         int diff = endNumber - startNumber;
    //         double t = timeInterval/diff;
             [NSThread sleepForTimeInterval: 0.01];

             if(diff==0){
                 return;
             }
             if(diff>0){
                 label.title= [NSString stringWithFormat:@"%d", startNumber + 1];
                 [self countup:label from:startNumber+1 to:endNumber];
             }
             if(diff<0){
                 label.title = [NSString stringWithFormat:@"%d", startNumber - 1];
                 [self countup:label from:startNumber-1 to:endNumber];
             }
        });
    }

不幸的是，这只是将我从我拥有的第一个号码带入，等待一段时间，然后将我带到我拥有的最后一个号码。

I've also tried the following with little luck: 

-(void)countup:(UIBarButtonItem *)label from:(int)startNumber to:(int)endNumber{
//         double timeInterval = 5; //5 seconds from start to stop
         int diff = endNumber - startNumber;
//         double t = timeInterval/diff;

         if(diff==0){
             return;
         }
         if(diff>0){
             label.title= [NSString stringWithFormat:@"%d", startNumber + 1];
             [self countup:label from:startNumber+1 to:endNumber];
             [NSTimer scheduledTimerWithTimeInterval:0.1
                                            target:self
                                            selector:@selector(callCountUp:)
                                            userInfo:[NSDictionary dictionaryWithObjectsAndKeys:label,
                                                      @"value1", startNumber, @"value2", endNumber, @"value3",nil]
                                            repeats:YES];
         }
         if(diff<0){
             label.title = [NSString stringWithFormat:@"%d", startNumber - 1];
             [self countup:label from:startNumber-1 to:endNumber];
         }
}

- (void)callCountUp:(NSTimer *)theTimer {
    UIBarButtonItem *value1 = [[theTimer userInfo] objectForKey:@"value1"];
    int value2 = (int)[[theTimer userInfo] objectForKey:@"value2"];
    int value3 = (int)[[theTimer userInfo] objectForKey:@"value3"];
    [self countup: value1 from:value2 to:value3];
}

【问题讨论】：

标签： ios multithreading count grand-central-dispatch nstimer

【解决方案1】：

您必须在主线程中更新显示在屏幕上的 UI 元素，因此您更改标签文本的每一行都必须包含在其中

dispatch_async(dispatch_get_main_queue){
    // change labels text
}

还有更好的方法来做你想做的事，你应该看看 NSTimer，例如你可以这样做

timer = [NSTimer scheduledTimerWithTimeInterval:1.0
                                 target:self
                               selector:@selector(updateTime)
                               userInfo:nil
                                repeats:YES];

这将每秒调用一次 updateTime 函数，直到你停止它

【讨论】：

我在将多个参数（基本上是一个递归函数）传递给 NSTimer 时遇到问题，我该怎么做？
@John 您可以查看如何在选择器中传递多个参数或尝试第一种方法
第一种方法 = 没有足够的论据？你能给我一个代码示例吗？
我尝试了以下但有一个错误：if(diff>0){ dispatch_async(dispatch_get_global_queue){ label.title= [NSString stringWithFormat:@"%d", startNumber + 1]; } [self countup:label from:startNumber+1 to:endNumber]; }
@John 我的错，我把“global”替换为“main”，检查一下试试，我的错

【解决方案2】：

以下代码最终为我工作：

-(void)countup:(UIBarButtonItem *)label from:(int)startNumber to:(int)endNumber{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        double diff = endNumber - startNumber;
        double t = 5;
        t = t/((diff*diff)+5);
        if(t<0){
            t=t*-1;
        }
        [NSThread sleepForTimeInterval: t];

        if(diff==0){
            return;
        }
        if(diff>0){
            dispatch_async(dispatch_get_main_queue(), ^{
                [UIView setAnimationsEnabled:NO];
                label.title= [NSString stringWithFormat:@"%d", startNumber + 1];
                [UIView setAnimationsEnabled:YES];
            });
            [self countup:label from:startNumber+1 to:endNumber];
        }
        if(diff<0){
            dispatch_async(dispatch_get_main_queue(), ^{
                label.title= [NSString stringWithFormat:@"%d", startNumber - 1];
            });
            [self countup:label from:startNumber-1 to:endNumber];
        }
    });
}

【讨论】：