我无法传回由我的自定义条码扫描器扫描的数据。 数据已成功读取,我可以将值分配给变量。但是我无法将数据传回之前的 View Controller 来填充 TextView 。
我在下面使用它传递给我的条形码 VC 以将数据存储在其中
var barcodeScanData: String = ""
我在下面使用 prepare for segue
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "BarcodeScanVC" {
let desitnationVC = segue.destination as! BarcodeScanVC
desitnationVC.xyz = barcodeScanData
}
}
下面是我尝试从我的自定义条码扫描仪发回数据的地方
var xyz: String = ""
func launchApp(barcodeScan: String) {
if presentedViewController != nil {
return
}
let alertPrompt = UIAlertController(title: "Barcode Found", message: "\(barcodeScan)", preferredStyle: .actionSheet)
let confirmAction = UIAlertAction(title: "Confirm", style: UIAlertAction.Style.default, handler: { (action) -> Void in
let barcodeData = PartsVCDetail()
self.xyz = barcodeScan
barcodeData.barcodeScanData = self.xyz
print(self.xyz, "This is what I am sending")
print(barcodeData.barcodeScanData, "This is what I am sending it TO" )
self.navigationController?.popViewController(animated: true)
})
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil)
alertPrompt.addAction(confirmAction)
alertPrompt.addAction(cancelAction)
present(alertPrompt, animated: true, completion: nil)
}
两条打印线
print(self.waybill, "This is what I am sending")
print(barcodeData.barcodeScanData, "This is what I am sending it TO"
但是,当我使用下面的最后一行时,显示正确的扫描数据:
self.navigationController?.popViewController(animated: true)
数据丢失,我在第一个 View Controller 的 viewDidAppear 中看到一个空值:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
print(barcodeScanData, "This is empty but it shouldnt be")
dataFromBarcodeScanner.text = barcodeScanData
}
我错过了什么?
最佳答案
使用此代码 let barcodeData = PartsVCDetail()
您将创建一个新的 PartsVCDetail
实例,然后设置该实例的属性。一旦操作结束,该实例将被释放,您将通过 popViewController
返回到之前的 View Controller 。
您的需求的常见解决方案是委托(delegate)模式。
- 您声明一个协议(protocol)供您的代表实现
- 您让原始 View Controller 实现此委托(delegate)协议(protocol)
- 您将原始 View Controller 设置为第二个 View Controller 的委托(delegate)
- 第二个 View Controller 可以调用委托(delegate)方法将数据传回
协议(protocol)
protocol BarcodeScanDelegate {
func didScan(barcodeData: String)
}
零件VCDetail
class PartsVCDetail: UIViewController, BarcodeScanDelegate {
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let desitnationVC = segue.destination as? BarcodeScanVC {
desitnationVC.delegate = self
}
}
func didScan(barcodeData: String) {
self.barcodeScanData = barcodeData
}
}
条码扫描VC
var delegate: BarcodeScanDelegate?
func launchApp(barcodeScan: String) {
guard presentedViewController == nil else {
return
}
let alertPrompt = UIAlertController(title: "Barcode Found", message: "\(barcodeScan)", preferredStyle: .actionSheet)
let confirmAction = UIAlertAction(title: "Confirm", style: UIAlertAction.Style.default, handler: { (action) -> Void in
self.delegate?.didScan(barcodeData: self.xyz)
self.navigationController?.popViewController(animated: true)
})
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil)
alertPrompt.addAction(confirmAction)
alertPrompt.addAction(cancelAction)
present(alertPrompt, animated: true, completion: nil)
}
关于ios - 自定义条码扫描仪,无法传回扫描数据,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54299153/