满足条件后如何快速停止活动指示器？

Question

我已将 UIActivityIndi​​catorView 声明为模型扩展中的计算属性。我有一个方法 configureCell 我试图将活动指示器用作 imageView 的子视图。在这里，我可以在特定条件下定位指标，但以后无法对其进行任何更改。例如，我无法停止活动指示器，无法更改颜色，甚至无法隐藏它。

extension TranscationModel: UITableViewDataSource, UITableViewDelegate
{

 var activityIN: UIActivityIndicatorView {
    var act = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray)
    act.color = UIColor.redColor()
    act.hidden = false
    act.startAnimating()
    return act
}

func configureTransactionCell(cell : TransactionCell?, indexPath: NSIndexPath) {
    if transaction.tid == "Something" {
        activityIN.color = UIColor.greenColor() //Even this doesn't work
        activityIN.center = cell.imgTransactionBill.center
        cell.imgTransactionBill.addSubview(activityIN)
        let delayTime = dispatch_time(DISPATCH_TIME_NOW, Int64(10 * Double(NSEC_PER_SEC)))
        dispatch_after(delayTime, dispatch_get_main_queue()) {
             activityIN.stopAnimating() //Not working
             activityIN.hidden = true   //Not working
        }
    }
}

Answer 1

您将activityIN 定义为计算变量。任何时候调用它，都会得到全新的实例。查看activityIN var 作为UIActivityIndicatorView 的便利初始化程序。如果您只需要十秒钟的活动，请像这样编辑您的功能：

func configureTransactionCell(cell : TransactionCell?, indexPath: NSIndexPath) {
    if transaction.tid == "Something" {
        let weakActivityIndicator = activityIN
        weakActivityIndicator.color = UIColor.greenColor()
        weakActivityIndicator.center = cell.imgTransactionBill.center
        cell.imgTransactionBill.addSubview(weakActivityIndicator)
        let delayTime = dispatch_time(DISPATCH_TIME_NOW, Int64(10 * Double(NSEC_PER_SEC)))
        dispatch_after(delayTime, dispatch_get_main_queue()) {
             weakActivityIndicator.stopAnimating()
             weakActivityIndicator.hidden = true
        }
    }
}

但通常您需要保留对从该初始化程序获得的实例的引用。在 TransactionCell 类中定义 UIActivityIndicatorView 存储属性。

假设TransactionCell 类有声明

var cellActivityIndicator: UIActivityIndicatorView!

然后你可以像这样编辑你的函数

func configureTransactionCell(cell : TransactionCell?, indexPath: NSIndexPath) {
    if transaction.tid == "Something" {
        cell.cellActivityIndicator = activityIN
        cell.cellActivityIndicator.color = UIColor.greenColor()
        cell.cellActivityIndicator.center = cell.imgTransactionBill.center
        cell.imgTransactionBill.addSubview(cell.cellActivityIndicator)
        let delayTime = dispatch_time(DISPATCH_TIME_NOW, Int64(10 * Double(NSEC_PER_SEC)))
        dispatch_after(delayTime, dispatch_get_main_queue()) {
             cell.cellActivityIndicator.stopAnimating()
             cell.cellActivityIndicator.hidden = true
        }
    }
}