Tableview加载

Question

在我的Xcode项目中，我将项目加载到Array，然后将其显示在UITableViewController上。虽然这些项加载UITableViewController是空的并且不美观，所以我想在加载数据时在UITableViewController中放置一个活动指示符。我在底部复制了我的代码。 我如何实现这个？（我听说称为完成处理程序的东西可能会做到这一点，但我不知道如何使用它）

func loadAnimals() {
    let animalQuery = PFQuery(className: "Animals")
    animalQuery.whereKey("userID", equalTo: PFUser.current()?.objectId! ?? String()) //getting which user
    animalQuery.limit = 10
    animalQuery.findObjectsInBackground { (objects, error) in
        if error == nil {
            self.colorArray.removeAll(keepingCapacity: false)
            self.animalNameArray.removeAll(keepingCapacity: false)                
            self.animalTypeArray.removeAll(keepingCapacity: false)

            for object in objects! {
                self.colorArray.append(object.value(forKey: "colorType") as! String) // add data to arrays
                self.animalNameArray.append(object.value(forKey: "animalName") as! String) // add data to arrays                    
                self.animalTypeArray.append(object.value(forKey: "animalType") as! String) // add data to arrays
            }
            self.tableView.reloadData()

        } else {
            print(error?.localizedDescription ?? String())
        }
    }
}

//在行中放置颜色

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! AnimalCell //connects to color cell

    //Adds the animal information in the cells
    cell.colorType.text = colorArray[indexPath.row] 
    cell.animalName.text = animalNameArray[indexPath.row] 
    cell.animalType.text = animalTypeArray[indexPath.row] 

    return cell
}

Answer 1

您似乎有一个用于加载表视图数据的异步函数。你只需要将activityIndicator.stopAnimating()放在那里。

以编程方式或通过UIActivityIndicatorView向表视图控制器添加Storyboard。 如果您选择在代码中执行此操作，则执行此操作，包括添加约束以将其保留在视图控制器的中间：

view.addSubview(activityIndicator)
activityIndicator.translatesAutoresizingMaskIntoConstraints = false
activityIndicator.hidesWhenStopped = true
activityIndicator.color = UIColor.black
let horizontalConstraint = NSLayoutConstraint(item: activityIndicator, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0)
view.addConstraint(horizontalConstraint)
let verticalConstraint = NSLayoutConstraint(item: activityIndicator, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: 0)
view.addConstraint(verticalConstraint)

在viewDidLoad()内调用上述代码之前，请在班级的某个地方声明let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .whiteLarge)。

您只需在loadAnimals开始执行后立即启动动画，并在调用tableView.reloadData()之前停止它。将其命名为`activityIndi​​cator，然后执行以下操作：

func loadAnimals() {
    activityIndicator.startAnimating()
    let animalQuery = PFQuery(className: "Animals")
    animalQuery.whereKey("userID", equalTo: PFUser.current()?.objectId! ?? String()) //getting which user
    animalQuery.limit = 10
    animalQuery.findObjectsInBackground { (objects, error) in
        if error == nil {
            self.colorArray.removeAll(keepingCapacity: false)
            self.animalNameArray.removeAll(keepingCapacity: false)                
            self.animalTypeArray.removeAll(keepingCapacity: false)

            for object in objects! {
                self.colorArray.append(object.value(forKey: "colorType") as! String) // add data to arrays
                self.animalNameArray.append(object.value(forKey: "animalName") as! String) // add data to arrays                    
                self.animalTypeArray.append(object.value(forKey: "animalType") as! String) // add data to arrays
            }
            activityIndicator.stopAnimating()
            self.tableView.reloadData()

        } else {
            print(error?.localizedDescription ?? String())
        }
    }
}

Answer 2

//SOMEWHERE ELSE IN YOUR CODE    
activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .whiteLarge) 
    activityIndicator.hidesWhenStopped = true
    self.view.addSubview(activityIndicator)

///.... where you load animals
func loadAnimals {
///
    activityIndicator.startAnimating()
     ////your code
     ///...
     animalQuery.findObjectsInBackground { (objects, error) in
       if error == nil {
        ///Stop the spinner
        activityIndicator.stopAnimating()
        ///...rest of your code
        }
       }