我正在使用CANBus adapter，当前正在Microsoft Visual C＃2010 Express中为其编写代码。我正在尝试制作一个运行单独线程的GUI，用于通过CANBus串行适配器读取来自TEKTRONIX 020-2924-XX DPO DEMO 2板的消息。
我试图找出终止线程的安全方法（称为setReceiveCallBackThread）。但是，这个特殊的线程是特殊的，因为线程的代码不可用。它是CANBus API的一部分。
我在网上搜索（特别是堆栈溢出）关于如何安全地停止线程。我发现使用abort方法应该永远是最后的手段。
因此，如果我决定不能在线程上使用abort，我将不得不在canplus_setReceiveCallBack子例程中使用异常处理。但问题是我无法访问canplus_setReceiveCallBack;代码是隐藏的。请记住，这是一种独特的情况，因为我无法访问代码。与可以看到回调函数代码的所有其他情况不同，此子例程中的代码无法看到。
下面的代码应该是分析问题所需的一切，并希望在线程上提供使用Abort（）的替代方法。
// CANSnifferForm.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Runtime.InteropServices;
using System.IO;
using System.Diagnostics;
namespace WindowsFormsApplication1
{
public partial class CANSnifferForm : Form
{
// per the api document. "This is a blocking call and must be called on a separate thread."
// the code previously after setCallback... was never being reached because the call is blocking.
// this calls the setCallbackThread function in another thread so processing can continue.
Thread setReceiveCallBackThread;
bool stop;
int can; // Return value of canplus_open
uint idFilter; // Filter values entered by user
ulong lenFilter;
bool stopThread; // Used for stopping thread
public CANSnifferForm()
{
InitializeComponent();
del = new EASYSYNC.CallbackDelegate(callback);
}
private void callback(ref EASYSYNC.CANMsg msg)
{
// Populate the dataGridView
if(InvokeRequired)
BeginInvoke(del, msg);
else
this.dataGridView1.Rows.Add(msg.id, msg.len, msg.data, msg.timestamp);
}
private EASYSYNC.CallbackDelegate del;
private void StartRestart_Click(object sender, EventArgs e)
{
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN closed");
this.ProcessStatusBox.Clear();
this.ProcessStatusBox.AppendText("Stopped");
EASYSYNC.CANMsg msg = new EASYSYNC.CANMsg();
msg.id = 1;
msg.timestamp = 2;
msg.flags = 3;
msg.len = 4;
msg.data = 5;
// Attempt to open CANBus adapter
can = EASYSYNC.canplus_Open(IntPtr.Zero, "1000", IntPtr.Zero, IntPtr.Zero, 0);
if (can < 0)
{
// CANBus Adapter not opened
this.ErrorBox.Clear();
this.ErrorBox.AppendText("Error opening CAN");
return;
}
// CANBus Adapter successfully opened
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN open");
// Initialize thread
setReceiveCallBackThread = new Thread(() => EASYSYNC.canplus_setReceiveCallBack(can, del));
// Attempt for CANBus adapter to listen
if (EASYSYNC.canplus_Listen(can) < 0)
{
// CANBus Adapter not listening
this.ErrorBox.Clear();
this.ErrorBox.AppendText("Error setting listen mode\n");
EASYSYNC.canplus_Close(can);
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN closed");
return;
}
// CANBus Adapter successfully listening
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN Listening\n");
// Place thread in background. Then start it
setReceiveCallBackThread.IsBackground = true;
setReceiveCallBackThread.Start();
while(!setReceiveCallBackThread.IsAlive);
this.ProcessStatusBox.Clear();
this.ProcessStatusBox.AppendText("Running\n");
}
private void FilterData_SelectedIndexChanged(object sender, EventArgs e)
{
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void Stop_Click(object sender, EventArgs e)
{
setReceiveCallBackThread.Abort(); // Stop thread
while (setReceiveCallBackThread.IsAlive == true)
{
}
this.ProcessStatusBox.Clear();
this.ProcessStatusBox.AppendText("Stopped");
// Attempt to flush CANBus Adapter
if (EASYSYNC.canplus_Flush(can) < 0)
{
// CANBus not flushing
this.ErrorBox.Clear();
this.ErrorBox.AppendText("Error flushing CAN");
EASYSYNC.canplus_Close(can); // Close CANBus Adapter
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN closed");
return;
}
// Attempt to reset CANBus Adapter
if (EASYSYNC.canplus_Reset(can) < 0)
{
// CANBus not resetting
this.ErrorBox.Clear();
this.ErrorBox.AppendText("Error resetting CAN");
EASYSYNC.canplus_Close(can); // Close CANBus Adapter
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN closed");
return;
}
this.CANSnifferStatusBox.Clear();
this.CANSnifferStatusBox.AppendText("CAN closed");
this.ErrorBox.Clear();
}
private void FilterID_KeyDown(object sender, EventArgs e)
{
}
private void FilterLength_KeyDown(object sender, EventArgs e)
{
}
private void FilterID_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
{
if (FilterIDBox.MaskFull)
{
}
else if (e.Position == FilterIDBox.Mask.Length)
{
}
else
{
}
}
private void FilterLength_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
{
if (FilterLengthBox.MaskFull)
{
}
else if (e.Position == FilterLengthBox.Mask.Length)
{
}
else
{
}
}
}
}
答案 0 :(得分：0)
我的原始答案不正确。根据API指南
定义一个将在所有传入上接收回调的函数 消息。这是一个阻塞调用，必须单独调用 线。要取消注册此回调函数， 可以使用等于NULL的cbfn调用canplus_setReceiveCallback。
该文档没有说明被阻止的呼叫何时会退出，所以我的猜测是当你用NULL调用canplus_setReceiveCallback时它会退出。
我没有办法轻松测试它，但您可以通过在原始调用返回时输出文本来验证这一点。
setReceiveCallBackThread = new Thread(() => { EASYSYNC.canplus_setReceiveCallBack(can, del); Trace.WriteLine("EASYSYNC thread terminated"); });
您的Stop_Click方法可以使用以下命令停止该线程：
EASYSYNC.canplus_setReceiveCallBack(can, null);