ios - TableView 单元格不显示更新的数据

Question

我达到了正确的值并在调试 session 期间打印了它。但是，当我运行应用程序时，计算值(新卡路里)不会显示特定的表格单元格文本字段。 (又名 cell.itemTotalCalory.text)您对解决方案有什么想法吗？

*我在下面附上了相关的代码块。

非常感谢，

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
    {

let cell = ingredientTableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! IngredientTableViewCell

        cell.ingredientNameTextField.text = ingredients [indexPath.row].ingredientName
        cell.numberofItem.text = "1"
        let cellcalory = ingredients [indexPath.row].ingredientCalory
        cell.itemTotalCalory.text = cellcalory

        cell.plusButton.tag = Int(cell.itemTotalCalory.text!)! //indexPath.row
        cell.plusButton.addTarget(self, action:#selector(plusAction), for: .touchUpInside)
        cell.minusButton.tag = Int(cell.itemTotalCalory.text!)!
        cell.minusButton.addTarget(self, action:#selector(minusAction), for: .touchUpInside)

        return cell
    }


@IBAction func plusAction(sender: UIButton)
    {

        let cell = ingredientTableView.dequeueReusableCell(withIdentifier: "cell") as! IngredientTableViewCell
        let buttonRow = sender.tag

        if cell.numberofItem.text == "1" || cell.numberofItem.text != "1"
        {
            cell.numberofItem.text = "1"
            let textValue1 = cell.numberofItem.text
            var textValue = Int(textValue1!)
            textValue = textValue! + 1
            cell.numberofItem.text = String(describing: textValue)

            let oldcalory = buttonRow
            cell.itemTotalCalory.text = String (((textValue! * Int(oldcalory)) + Int(oldcalory)))
            let newcalory = cell.itemTotalCalory.text

            refresh(newcalory: newcalory!);     

        }
    }

func refresh(newcalory :String)
    {

       let cell = ingredientTableView.dequeueReusableCell(withIdentifier: "cell") as! IngredientTableViewCell
        cell.itemTotalCalory.text = newcalory

        DispatchQueue.main.async {
            self.ingredientTableView.reloadData()
        }    
    }

Answer 1

您应该做的是更新 ingredients 数组中的值，然后调用 ingredientTableView.reloadData() 将其反射(reflect)到 UI。

调用dequeueReusableCell(withIdentifier:)在 refresh 方法中将无法按预期执行您想要执行的操作:

For performance reasons, a table view’s data source should generally reuse UITableViewCell objects when it assigns cells to rows in its tableView(_:cellForRowAt:) method. A table view maintains a queue or list of UITableViewCell objects that the data source has marked for reuse. Call this method from your data source object when asked to provide a new cell for the table view. This method dequeues an existing cell if one is available or creates a new one using the class or nib file you previously registered. If no cell is available for reuse and you did not register a class or nib file, this method returns nil.

所以，刷新方法应该类似于:

func refresh() {
    // updating ingredients array upon reqs satisfaction...
    // and then:
    ingredientTableView.reloadData()

    // nameOfYourRefreshControl.endRefreshing()
}

此外，如果您非常确定要从 tableView 获取特定单元格，则可能需要使用 cellForRow(at:)实例方法:

Returns the table cell at the specified index path.

func refresh() {
    let cell = ingredientTableView?.cellForRow(at: YOUR_INDEX_PATH)

    //...
}

希望这有帮助。