我有一个问题，我无法提出解决方案。关于我在wm 6.5和Compact Framework 2.0上使用motorola MC3190-G手持应用程序的应用程序
在我的应用程序中实现使用扫描程序触发器的符号包之后，每次关闭我的应用程序/或启用了扫描程序的表单时，我都会收到以下错误： （即使我从未收到扫描数据）
我在stackoverflow和其他网站上搜索了一个没有解决方案的解决方案。
我是移动应用程序开发的新手。我尝试捕获一切，但错误似乎无法捕获异常类型“异常”。
抱歉英语不好。错误：
的NullReferenceException
在MainForm.SymbolReader_ReadNotifiy（）
在
Task.Invoke（）
在
System.Windows.Forms.Control._InvokeAll（）
在
System.Windows.Forms.Control.WinProc（）
信息：
摩托罗拉EMDK 2.6 装置：MC3190-G
源码：
Scanner.cs
namespace MyScann
{
/// <summary>
/// Summary description for Scanner.
/// </summary>
public class Scanner
{
public static Symbol.Barcode.Reader SymbolReader = null;
public static Symbol.Barcode.ReaderData SymbolReaderData = null;
public static System.EventHandler SymbolEventHandler = null;
public static DataSet CodeDataSet;
//public static Utils.Sound ReadErrorSound;
public static bool ScannerEnabled = false;
public static void ActivateScanner()
{
// If we have both a reader and a reader-data Object
if ( Scanner.SymbolReader != null &&
Scanner.SymbolReaderData != null &&
! Scanner.SymbolReaderData.IsPending )
{
// Submit 'Read'
try
{
Scanner.SymbolReader.Actions.Read(Scanner.SymbolReaderData);
}
catch (Exception err)
{
MessageBox.Show(err.Message);
if ( err.InnerException != null )
MessageBox.Show(err.InnerException.Message);
}
}
}
public static void DeactivateScanner()
{
// If we have both a reader and a reader-data Object
if ( Scanner.SymbolReader != null &&
Scanner.SymbolReaderData != null &&
Scanner.SymbolReaderData.IsPending )
{
// Submit 'CancelRead'
try
{
Scanner.SymbolReader.Actions.CancelRead(Scanner.SymbolReaderData);
}
catch (Exception err)
{
MessageBox.Show(err.Message);
if ( err.InnerException != null )
MessageBox.Show(err.InnerException.Message);
}
}
}
/// <summary>
/// Initialize the reader.
/// </summary>
/// <returns>False if an error accurs</returns>
public static bool InitSymbolReader()
{
// If reader is already present then fail initialize
if ( SymbolReader != null )
{
return false;
}
// Create new reader, first available reader will be used.
SymbolReader = new Symbol.Barcode.Reader();
// Create reader data
SymbolReaderData = new Symbol.Barcode.ReaderData(
Symbol.Barcode.ReaderDataTypes.Text,
Symbol.Barcode.ReaderDataLengths.DefaultText);
// set scanner read error sound
//ReadErrorSound = new Utils.Sound(ErrorSound);
return true;
}
/// <summary>
/// Stop reading and disable/close reader
/// </summary>
public static void DeinitSymbolReader()
{
try
{
// If we have a reader
if ( SymbolReader != null )
{
//Cancel Incoming Requests
SymbolReader.Actions.Flush();
// Disable the reader
SymbolReader.Actions.Disable();
// Free it up
SymbolReader.Dispose();
// Indicate we no longer have one
SymbolReader = null;
}
// If we have a reader data
if ( SymbolReaderData != null )
{
// Free it up
SymbolReaderData.Dispose();
// Indicate we no longer have one
SymbolReaderData = null;
}
if(SymbolEventHandler!=null){
//SymbolEventHandler(this,null);
SymbolEventHandler = null;
}
}
catch (Exception e){MessageBox.Show(e.StackTrace.ToString());
}
}
/// <summary>
/// Enable most barcode type with no limitation on length
/// </summary>
public static void OpenAllBarcodes()
{
SymbolReader.Decoders.CODABAR.Enabled = true;
SymbolReader.Decoders.CODABAR.MinimumLength = 0;
SymbolReader.Decoders.CODABAR.MaximumLength = 0;
SymbolReader.Decoders.CODE11.Enabled = true;
SymbolReader.Decoders.CODE11.MinimumLength = 0;
SymbolReader.Decoders.CODE11.MaximumLength = 0;
SymbolReader.Decoders.CODE39.Enabled = true;
SymbolReader.Decoders.CODE39.MinimumLength = 0;
SymbolReader.Decoders.CODE39.MaximumLength = 0;
SymbolReader.Decoders.CODE93.Enabled = true;
SymbolReader.Decoders.CODE93.MinimumLength = 0;
SymbolReader.Decoders.CODE93.MaximumLength = 0;
SymbolReader.Decoders.CODE128.Enabled = true;
SymbolReader.Decoders.CODE128.MinimumLength = 0;
SymbolReader.Decoders.CODE128.MaximumLength = 0;
SymbolReader.Decoders.DATAMATRIX.Enabled = true;
SymbolReader.Decoders.DATAMATRIX.MinimumLength = 0;
SymbolReader.Decoders.DATAMATRIX.MaximumLength = 0;
SymbolReader.Decoders.D2OF5.Enabled = true;
SymbolReader.Decoders.D2OF5.MinimumLength = 0;
SymbolReader.Decoders.D2OF5.MaximumLength = 0;
SymbolReader.Decoders.I2OF5.Enabled = true;
SymbolReader.Decoders.I2OF5.MinimumLength = 0;
SymbolReader.Decoders.I2OF5.MaximumLength = 0;
/*
SymbolReader.Decoders.EAN13.Enabled = true;
SymbolReader.Decoders.EAN13.MinimumLength = 0;
SymbolReader.Decoders.EAN13.MaximumLength = 0;
SymbolReader.Decoders.EAN8.Enabled = true;
SymbolReader.Decoders.EAN8.MinimumLength = 0;
SymbolReader.Decoders.EAN8.MaximumLength = 0;
SymbolReader.Decoders.PDF417.Enabled = true;
SymbolReader.Decoders.PDF417.MinimumLength = 0;
SymbolReader.Decoders.PDF417.MaximumLength = 0;
SymbolReader.Decoders.UPCA.Enabled = true;
SymbolReader.Decoders.UPCA.MinimumLength = 0;
SymbolReader.Decoders.UPCA.MaximumLength = 0;
SymbolReader.Decoders.UPCE1.Enabled = true;
SymbolReader.Decoders.UPCE1.MinimumLength = 0;
SymbolReader.Decoders.UPCE1.MaximumLength =0;
SymbolReader.Decoders.UPCE0.Enabled = true;
SymbolReader.Decoders.UPCE0.MinimumLength = 0;
SymbolReader.Decoders.UPCE0.MaximumLength = 0;
*/
SymbolReader.Parameters.CodeIdType = Symbol.Barcode.CodeIdTypes.None;
SymbolReader.Parameters.ScanType = Symbol.Barcode.ScanTypes.Background;
SymbolReader.Parameters.LocalFeedback = Symbol.Barcode.DisabledEnabled.Enabled;
Scanner.SymbolReader.Parameters.Feedback.Success.BeepTime = 0;
}
}
}
}
在MainForm.cs内部
public void InitScanner(byte BatteryLevel)
{
// Create event handler delegate
if (Scanner.MyScann.Scanner.SymbolEventHandler == null)
{
Scanner.MyScann.Scanner.SymbolEventHandler = new EventHandler(this.SymbolReader_ReadNotify);
// Enable reader, with wait cursor
Scanner.MyScann.Scanner.SymbolReader.Actions.Enable();
Scanner.MyScann.Scanner.OpenAllBarcodes();
Scanner.MyScann.Scanner.ScannerEnabled = true;
}
// If we have both a reader and a reader data
if ((Scanner.MyScann.Scanner.SymbolReader != null) &&
(Scanner.MyScann.Scanner.SymbolReaderData != null))
{
// Submit a read
Scanner.MyScann.Scanner.SymbolReader.ReadNotify += Scanner.MyScann.Scanner.SymbolEventHandler;
Scanner.MyScann.Scanner.SymbolReader.Actions.Read(Scanner.MyScann.Scanner.SymbolReaderData);
}
}
public void SymbolReader_ReadNotify(object sender, EventArgs e)
{
Symbol.Barcode.ReaderData TheReaderData = Scanner.MyScann.Scanner.SymbolReader.GetNextReaderData();
if (TheReaderData.Result == Symbol.Results.SUCCESS /*&& (txtBarcode.Focused == true)*/)
{
// if (txtBarcode.Focused == true)
// {
// txtBarcode.Text = TheReaderData.Text.ToString();
MessageBox.Show(TheReaderData.Text.ToString());
SymbolReader_CycleScannerReader();
return;
// }
}
SymbolReader_CycleScannerReader();
}
public void SymbolReader_CycleScannerReader()
{
Scanner.MyScann.Scanner.SymbolReader.Actions.Read(Scanner.MyScann.Scanner.SymbolReaderData);
}
public void StartScanner()
{
bool flag = false;
try
{
Scanner.MyScann.Scanner.SymbolEventHandler = null;
Scanner.MyScann.Scanner.DeinitSymbolReader();
Scanner.MyScann.Scanner.ScannerEnabled = false;
if (!Scanner.MyScann.Scanner.ScannerEnabled)
{
Scanner.MyScann.Scanner.SymbolEventHandler = null;
Scanner.MyScann.Scanner.InitSymbolReader();
InitScanner(100);
flag = true;
}
}
catch
{
Scanner.MyScann.Scanner.SymbolEventHandler = null;
Scanner.MyScann.Scanner.InitSymbolReader();
InitScanner(100);
flag = true;
}
finally
{
if (!flag)
{
MessageBox.Show("Scanner Error");
}
}
}
void public void CloseScanner()
{
Scanner.MyScann.Scanner.SymbolEventHandler = null;
Scanner.MyScann.Scanner.DeinitSymbolReader();
}
void MainFormLoad(object sender, EventArgs e)
{
StartScanner();
}
void MainFormClosing(object sender, System.ComponentModel.CancelEventArgs e)
{
CloseScanner();
}
void ButtonExitClick(object sender, EventArgs e)
{
Scanner.MyScann.Scanner.DeinitSymbolReader();
this.Close();
Application.Exit();
}
任何帮助将不胜感激！
答案 0 :(得分：1)
我不熟悉符号库，但从我可以看到的问题是在扫描仪的“取消初始化”后的某个时刻出现 ReadNotify 事件。
您应该在 MainForm.CloseScanner（）中执行的操作是先删除 MainForm.InitScanner（）中添加的所有句柄，然后调用 Scanner .DeinitSymbolReader（）
编辑： 您应该使用 - = 运算符删除句柄，而不是指定空引用。
希望这有帮助。
答案 1 :(得分：0)
尝试在退出时不调用'DeinitSymbolReader'，看看是否修复了它
皮特
答案 2 :(得分：0)
我的印象是，使用或不使用'deinitSymbolReader'时，您的应用程序无法正确退出。通过在已经关闭的资源上调用deinitSymbolReader可能会导致访问冲突。 也许您应该尝试放弃deinintSymbolReader，并尝试在Form的Disposing Event中处理扫描仪/触发器。
似乎问题在于您正在处理复杂的数据结构，而且您正在将它们更改为null，这基本上意味着您正在更改引用，并且可能确保GC永远不会释放所有未经管理的资源。
您正在处理对未受管理资源的不当操作的一个迹象是，第二个deinintSymbolReader不应该执行任何操作（因为所有资源都为null），因此更少导致错误。
我有一个使用触发器和扫描程序的应用程序，如果扫描程序不为空，它只需要“enableScanner = false”和“Scanner.Dispose（）”。