將手勢識別器功能中的變量傳遞給IBAction

Question

我有一個簡單的應用程序，其中包含CollectionView及其中的項目。 長按cell彈出UIView出現一個TextField和一個選項將其保存在對應於cellarray。

這裏是代碼（buttons和gestures已經在viewDidLoad()方法正確添加）：

class CollectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate { 
var longPressedPoint: CGPoint? 

public var rowOfLongPressedItem: Int? = nil 

func handleLongPress(longPressRecognizer: UILongPressGestureRecognizer) -> Int  { 
    print("LONG PRESS Gesture Recognized") 
    notePopup.hidden = false 
    longPressedPoint = longPressRecognizer.locationInView(longPressRecognizer.view) 
    var indexPathOfLongPressedCell = self.itemCollectionView.indexPathForItemAtPoint(longPressedPoint!) 
    rowOfLongPressedItem = (indexPathOfLongPressedCell?.row) 
    print("rowOfLongPressedItem -> .\(rowOfLongPressedItem)") 
    return rowOfLongPressedItem! 
} 

func saveNoteButtonTapped(rowOfLongPressedItem: Int) { 
    print("rowOfLongPressedItem when Save button is tapped -> .\(rowOfLongPressedItem)")  

    //Can’t go further down as rowOfLongPressedItem is NOT available from 「handleLongPress」 function… 

    var selectedItem = ItemsList[rowOfLongPressedItem] 
    selectedItem.counts += 1 
    var latest = selectedItem.counts - 1 
    selectedItem.timestamp.append(NSDate()) 
    selectedItem.note.append(noteTextField.text) 
    ItemsList[rowOfLongPressedItem] = selectedItem 
    print(".\(selectedItem.title) has been tapped .\(selectedItem.counts)") 
    print("The latest tap on .\(selectedItem.title) is at .\(selectedItem.timestamp[latest])") 
    print("The note .\(noteTextField.text) has been added") 
    notePopup.hidden = true 
} 
} 

試圖解決的問題在幾個方面：

• 在定義一個變量View Controller希望函數返回值並將其保存在全局變量中。 但是，後來從Apple發現， 「函數不能具有比其參數類型和返回類型更高的訪問級別，因爲該函數可用於其構成類型不可用於周圍代碼的情況。」 https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/AccessControl.html

• 我試圖把按鈕的選擇功能碼長按手勢功能的內部，使得它的返回值是容易獲得的。但是，我無法調用Selector函數，因爲它在另一個函數中。

• 此外，我試着返回長按手勢功能的值，並在保存按鈕的IBAction中使用它。但是，爲此，我需要再次調用handleLongPress，然後longPressedPoint被檢測爲保存按鈕內部。因此，​​是nil和應用程序崩潰。

有人可以幫我...

Answer 1

假設你想獲得所選單元格的行，並將其分配給全局變量rowOfLongPressedItem，你不需要讓handleLongPress返回一個int。

注意：這是一個斯威夫特3碼（具有相同的概念）：

public var rowOfLongPressedItem: Int? = nil 

override func viewDidLoad() { 
    //... 

    let longPressRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(ViewController.assignRowOfLongPressedItem)) 

    itemCollectionView.addGestureRecognizer(longPressRecognizer) 

    //... 
} 

func assignRowOfLongPressedItem(longPressRecognizer: UILongPressGestureRecognizer) { 
    let longPressedPoint = longPressRecognizer.location(in: longPressRecognizer.view) 
    var indexPathOfLongPressedCell = self.itemCollectionView.indexPathForItem(at: longPressedPoint) 
    rowOfLongPressedItem = (indexPathOfLongPressedCell?.row) 
    // if you long press the first row -for example-, the output should be: "rowOfLongPressedItem -> .Optional(0)" 
    print("rowOfLongPressedItem -> .\(rowOfLongPressedItem)") 
} 

而且，你不需要讓saveNoteButtonTapped採取rowOfLongPressedItem參數。需要注意的是rowOfLongPressedItem是可選的，你應該確保它不是仍然爲零（你可以使用Early Exit方法）：

func saveNoteButtonTapped(sender: UIButton) { 
     guard let selectedCellRow = rowOfLongPressedItem else { 
      print("rowOfLongPressedItem is nil!!") 
      return 
     } 

     print("rowOfLongPressedItem when Save button is tapped -> .\(selectedCellRow)") 
     var selectedItem = ItemsList[selectedCellRow] 

     selectedItem.counts += 1 
     var latest = selectedItem.counts - 1 
     selectedItem.timestamp.append(NSDate()) 
     selectedItem.note.append(noteTextField.text) 
     ItemsList[row] = selectedItem 
     print(".\(selectedItem.title) has been tapped .\(selectedItem.counts)") 
     print("The latest tap on .\(selectedItem.title) is at .\(selectedItem.timestamp[latest])") 
     print("The note .\(noteTextField.text) has been added") 
     notePopup.hidden = true 
} 

Answer 2

rowOfLongPressedItem可用於兩種功能。您無需將其設置爲saveNoteButtonTapped的參數。

var rowOfLongPressedItem: Int? = nil 

func handleLongPress(longPressRecognizer: UILongPressGestureRecognizer) -> Int  { 
    print("LONG PRESS Gesture Recognized") 
    notePopup.hidden = false 
    longPressedPoint = longPressRecognizer.locationInView(longPressRecognizer.view) 
    var indexPathOfLongPressedCell = self.itemCollectionView.indexPathForItemAtPoint(longPressedPoint!) 
    rowOfLongPressedItem = (indexPathOfLongPressedCell?.row) 
    print("rowOfLongPressedItem -> .\(rowOfLongPressedItem)") 
    return rowOfLongPressedItem! 
} 

func saveNoteButtonTapped() { 

    guard let row = rowOfLongPressedItem else { 
     return // rowOfLongPressedItem was nil 
    } 

    print("rowOfLongPressedItem when Save button is tapped -> .\(row)") 
    var selectedItem = ItemsList[row] 

    selectedItem.counts += 1 
    var latest = selectedItem.counts - 1 
    selectedItem.timestamp.append(NSDate()) 
    selectedItem.note.append(noteTextField.text) 
    ItemsList[row] = selectedItem 
    print(".\(selectedItem.title) has been tapped .\(selectedItem.counts)") 
    print("The latest tap on .\(selectedItem.title) is at .\(selectedItem.timestamp[latest])") 
    print("The note .\(noteTextField.text) has been added") 
    notePopup.hidden = true 
}