objective-c - 根据标签设置 UIImage

Question

我正在编写一个循环遍历 LED UIImageView 数组的脚本，这些 LED UIImageView 以数字顺序设置并由标签选择。根据步骤(又名数字)，它在 LED 图像上显示为打开或关闭。此方法的主要目标是执行当前步骤并显示“LED 开启”图像，同时将其减一并显示上一步的“LED 关闭”图像。因此，一次只能点亮一个 LED。

不幸的是，我只能让“LED on”图像正确显示。序列中的所有 LED 都会亮起，但它们永远不会熄灭。我的第一个猜测是我没有以正确的方式减去 NSInterger。但是，当我检查日志时，一切都在它应该在的地方。如果当前步骤为 2，则上一步为 1。不知道为什么这不起作用。谢谢!

sequencerLocation 和 previousLocation 都设置为属性。

- (void)clockLoop:(UInt8)seqClockPulse
{
//cast to an int to use in loop
NSInteger stepCount = sequencerSteps;

//increment sequencer on pulse in
sequencerLocation++;

if(sequencerLocation > stepCount)
{
    sequencerLocation = 1;
}

//setup previous step location
previousLocation = (sequencerLocation - 1);

if (previousLocation == 0)
{
    previousLocation = stepCount;
}

//change led color in led array
for (UIImageView *led in sequencerLEDArray)
{
    if(led.tag == sequencerLocation)
    {
        UIImageView *previousLed = (UIImageView *)[led viewWithTag:previousLocation];
        [previousLed setImage:[UIImage imageNamed:@"images/seq_LED_off.png"]];
        NSLog(@"Previous: %d", previousLocation);

        UIImageView *currentLed = (UIImageView *)[led viewWithTag:sequencerLocation];
        [currentLed setImage:[UIImage imageNamed:@"images/seq_LED_on.png"]];
        NSLog(@"Current: %d", sequencerLocation);
    }
}

}

Answer 1

//change led color in led array
for (UIImageView *led in sequencerLEDArray)
{
if(led.tag == sequencerLocation)
{
    //  I THINK the problem is here
  //  UIImageView *previousLed = (UIImageView *)[led viewWithTag:previousLocation];
    //  TRY THIS instead
    UIImageView *previousLed = [led.superview viewWithTag:previousLocation];
    [previousLed setImage:[UIImage imageNamed:@"images/seq_LED_off.png"]];
    NSLog(@"Previous: %d", previousLocation);

    // HERE you don't need to search for the tag you already tested for it in your if statement
    UIImageView *currentLed = (UIImageView *)[led viewWithTag:sequencerLocation];
    [currentLed setImage:[UIImage imageNamed:@"images/seq_LED_on.png"]];
    NSLog(@"Current: %d", sequencerLocation);
}
}

viewWithTag:
Discussion

This method searches the current view and all of its subviews for the specified view.

所以当你搜索 led通过它自己的标签，它正在返回自己，但是当你搜索它的兄弟时它没有找到它，这就是我建议 led.superview 的原因作为搜索标签的地方， parent 应该能够找到它的另一个 child 。