Question

我正在关注this教程如何避免UITableView的滞后，但人口数据效果不佳。有时显示错误的数据并且不再更改，或者显示错误然后切换到正确的数据。

我怎么能解决这个问题？

这是教程中需要的课程

class SerialOperationQueue: OperationQueue
{
    override init()
    {
        super.init()
        maxConcurrentOperationCount = 1
    }
}

然后在VehicleCell课程中我有

let queue = SerialOperationQueue()

在模型方法中，从教程中可以看出：

模板：

func setSomething(vehicle: VehicleModel) -> String {
        Thread.sleep(forTimeInterval: 0.01)
        return "some string from model"
    }

在UITableViewDataSource我有

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        return vehiclesTableView.dequeueReusableCell(withIdentifier: "vehicleCell", for: indexPath) as! VehiclesCell   
    }

和willDisplay

 func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        if let cell = cell as? VehiclesCell {
            configureCell(cell: cell, indexPath: indexPath)
        }

cell.alpha = 0
        cell.layer.transform = CATransform3DMakeScale(0.1, 0.1, 1)

        cell.layoutIfNeeded()
        cell.layer.removeAllAnimations()
        UIView.animate(withDuration: 0.3, delay: 0, options: .curveEaseOut, animations: {
            cell.alpha = 1
            cell.layer.transform = CATransform3DMakeScale(1, 1, 1)
            cell.layoutIfNeeded()
        })
    }

private func configureCell(cell: VehiclesCell, indexPath: IndexPath) {

        cell.queue.cancelAllOperations()
        let operation: BlockOperation = BlockOperation()

        operation.addExecutionBlock {
            let vehicles = self.checkForVehicles(inSection: indexPath.section)
            let vehicle = vehicles[indexPath.row]
            let vehicleName = self.setVehicleName(vehicle: vehicle)
            let driverName = self.setDriverName(vehicle: vehicle)
            let topColor = self.setTopLineColor(vehicle: vehicle, colorView: cell.topColorView)
            let vehicleImage = self.setVehicleImage(vehicle: vehicle)
            let address = self.setAddress(vehicle: vehicle)
            let engineStatus = self.setEngineStatus(vehicle: vehicle)
            let hosStatus = self.setHosStatus(vehicle: vehicle)
            let speed = self.setSpeed(vehicle: vehicle)
            DispatchQueue.main.async {

                if operation.isCancelled { return }

                cell.vehicleNameLabel.text = vehicleName
                cell.driverNameLabel.text = driverName
                cell.topColorView = topColor
                cell.vehicleImageView.image = vehicleImage
                cell.localizationLabelView.text = address
                cell.engineLabel.text = engineStatus
                cell.hosStatusLabel.text = hosStatus
                cell.speedValueLabel.text = speed
            }
        }

        cell.queue.addOperation(operation)
    }

有人能解释我这种行为吗？为什么单元格填充了错误的数据，然后当它们变得正确时，它们会切换。他们可能会保持这样状态而不会转换为良好的数据吗？

解决这个问题的最佳选择是什么？

提前致谢！

Answer 1

问题是您没有覆盖VehicleCell中的prepareForReuse function。

由于单元格在UITableView中被重用以获得更平滑的性能，因此它会重复使用tableView中的单元格，而不是每次需要新单元格时都创建新实例。

执行此操作时：

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        return vehiclesTableView.dequeueReusableCell(withIdentifier: "vehicleCell", for: indexPath) as! VehiclesCell   
}

而不是创建新的单元格，您可以使用标识符对可重复使用的单元格进行出列。

因此，重要的是，您覆盖perpareForReuse函数。查看您的VehicleCell界面，它应该如下所示：

override func prepareForReuse() {
    super.prepareForReuse()
    self.vehicleNameLabel.text = nil
    self.driverNameLabel.text = nil
    self.topColorView = nil
    self.vehicleImageView.image = nil
    self.localizationLabelView.text = nil
    self.engineLabel.text = nil
    self.hosStatusLabel.text = nil
    self.speedValueLabel.text = nil
}

willDisplayCell中的所有代码都是不需要的代码，什么不起作用，根本就没有意义。

修改我喜欢configureCell方法，但不喜欢使用队列。所以我建议你做以下事情：

删除willDisplay功能。

从configureCell
中删除所有此BlockOperation和队列相关代码
从configureCell致电cellForRowAt，并在设置完成后返回

```

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell: VehiclesCell = vehiclesTableView.dequeueReusableCell(withIdentifier: "vehicleCell", for: indexPath) as! VehiclesCell self.configureCell(cell: cell, indexPath: indexPath) return cell } private func configureCell(cell: VehiclesCell, indexPath: IndexPath) { let vehicles = self.checkForVehicles(inSection: indexPath.section) let vehicle = vehicles[indexPath.row] let vehicleName = self.setVehicleName(vehicle: vehicle) let driverName = self.setDriverName(vehicle: vehicle) let topColor = self.setTopLineColor(vehicle: vehicle, colorView: cell.topColorView) let vehicleImage = self.setVehicleImage(vehicle: vehicle) let address = self.setAddress(vehicle: vehicle) let engineStatus = self.setEngineStatus(vehicle: vehicle) let hosStatus = self.setHosStatus(vehicle: vehicle) let speed = self.setSpeed(vehicle: vehicle) cell.vehicleNameLabel.text = vehicleName cell.driverNameLabel.text = driverName cell.topColorView = topColor cell.vehicleImageView.image = vehicleImage cell.localizationLabelView.text = address cell.engineLabel.text = engineStatus cell.hosStatusLabel.text = hosStatus cell.speedValueLabel.text = speed }

```

修复UITableVIew滞后

1 个答案: