ios - 如何在 View 上继续动画刷新控件已更改

Question

我在选项卡栏 Controller 内的 View “A”中有一个表。当我向下滚动以重新加载表格刷新控件时开始动画。当按标签栏 Controller 进入 View “B”然后返回查看“A”时，刷新控件可见但没有动画。

有人可以帮助我吗？谢谢

func refresh(sender:AnyObject)
{
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), { () -> Void in

    Call API for data
    dispatch_async(dispatch_get_main_queue(), { () -> Void in

                UPDATE UI
                refreshControl.endRefreshing()

            })
        });
}

override func viewDidAppear(animated: Bool)
{
    if(requestTerminated == false)
    {
       //Continue animate refresh control somehow
    }
}

Answer 1

假设您在 Controller A 中遇到这种情况，例如在 viewDidLoad 中:

//global var
var refreshControl:UIRefreshControl!

self.refreshControl = UIRefreshControl()
self.refreshControl.attributedTitle = NSAttributedString(string: "pull to refresh")
self.refreshControl.addTarget(self, action: #selector(MyTableViewController.pullToRefresh(_:)), forControlEvents: UIControlEvents.ValueChanged)
self.tableView.addSubview(refreshControl)

如您所见，您已将 refreshControl 作为 subview 添加到 A 表 Controller 。当您转到另一个 Controller 时，您可能会显示另一个 Controller (B)，当您返回 A 时，您的刷新被卡住或卡住。

您可以在 viewWillAppear 上启动 UIRefreshControl 动画并在 viewDidDisappear 上结束它。在转换期间保存刷新过程的状态以了解何时显示 UIRefreshControl。

您可以像这样使用 bool 值:

// Refresh state
var isRefreshing = false

// Call on viewWillApper
func superviewWillApper(){
    if isRefreshing && !refreshControl.refreshing{
        startRefreshAnimation()
    }
}

// Call on viewDidDisapper
func superviewDidDisappear(){
    endRefreshAnimation(false, dataFetched: !isRefreshing)
}

func startRefreshAnimation(){
    refreshControl.beginRefreshing()
    contentOffset = CGPointMake(0, -refreshControl.bounds.size.height)

    isRefreshing = true
}

//Saves state of refresh
func endRefreshAnimation(wasEmpty: Bool, dataFetched: Bool){
    refreshControl.endRefreshing()
    isRefreshing = !dataFetched
    if !wasEmpty{
        setContentOffset(CGPointZero, animated: true)
    }else{
        setContentOffset(CGPointZero, animated: false)
    }
}