WinCE5.0移动平台开发笔记(OpenNETCF.Desktop.Communication连接和断开使用心得)

当用PC机读取和操作PDA时候，需要用到RAPI,那么为了更好的使用RAPI，我们会使用到OpenNETCF.Desktop.Communication.dll文件，这个文件在Rapi.dll(win32 api)的基础上进行了NET封装。我们更能方便的使用它。对于连接和断开移动设备的方法，在使用过程中出现了一点问题，这里将记录下来，和朋友们分享：

1、当我们首先实例化时：RAPI m_rapi = new RAPI();调用：m_rapi.Connect(false, 2).如果当PDA和PC没有连接成功时候，根据OpenNetCF.Desktop.Communication里面的方法，就会在子线程中抛出异常，主线程不能Catch获取子线程中异常，导致程序无法正常运行下去。相关代码如下：

WinCE5.0移动平台开发笔记(OpenNETCF.Desktop.Communication连接和断开使用心得)

代码

     public void Connect( bool WaitForInit, int TimeoutSeconds)
        {
             int ret = 0 ;
            m_timeout = TimeoutSeconds;

             if (WaitForInit)
            {
                ret = CeRapiInit();
                 if ( ret != 0 )
                {
                     int e = CeRapiGetError();

                    Marshal.ThrowExceptionForHR(ret);
                }

                 lock ( this )
                {
                    m_connected = true ;
                }

                 // throw the connected event
                 if (RAPIConnected != null )
                {
                    RAPIConnected();
                }

                 return ;
            }

             // non-blocking init call
            m_ri = new RAPIINIT();

            m_ri.cbSize = Marshal.SizeOf(m_ri);
            m_ri.hrRapiInit = m_InitResult;

            m_hInitEvent = CreateEvent(IntPtr.Zero, 0 , 0 , " OpenNETCF.RAPI " );

             if (( uint )m_hInitEvent == uint .MaxValue)
            {
                 throw new RAPIException( " Failed to Initialize RAPI " );
            }

            m_ri.heRapiInit = m_hInitEvent;

            ret = CeRapiInitEx( ref m_ri);
             if (ret != 0 )
            {
                Marshal.ThrowExceptionForHR(ret);
            }

             // create a wait thread
            m_initThread = new Thread( new ThreadStart(InitThreadProc));

             // Start thread
            m_initThread.Start();
        }
        private void InitThreadProc()
        {
             int ret = 0 ;
             int timeout = m_timeout * 4 ;
             bool infinitetimeout = (timeout < 0 );

             // check for Init event 4 times / sec
             do
            {
                 // check for abort command from Dispose()
                 if (m_killThread)
                {
                     return ;
                }

                 // see if the event is set
                ret = WaitForSingleObject(m_ri.heRapiInit, 250 );

                 if ((ret == WAIT_FAILED) || (ret == WAIT_ABANDONED))
                {
                     throw new RAPIException( " Failed to Initialize RAPI " );
                }

                 if ( ! infinitetimeout)
                {
                     if (timeout -- < 0 )
                    {
                         throw new RAPIException( " Timeout waiting for device connection " );
                    }
                }
            } while (ret != WAIT_OBJECT_0);

             // check the hresult
             if (m_InitResult != 0 )
            {
                Marshal.ThrowExceptionForHR(m_InitResult);
            }

             lock ( this )
            {
                m_connected = true ;
            }

             // throw the connected event
             if (RAPIConnected != null )
            {
                RAPIConnected();
            }

             // clean up
            CloseHandle(m_hInitEvent);
        }

上面的代码当我们调用m_rapi.Connect(false,2)时候，最终在子线程中抛出异常:Timeout waiting for device connection

为了在主线程中捕捉在子线程中出现的异常，我们对上面的代码做一些修改：

代码

     public delegate void ExceptionEventHandler(RAPIException e);
     public event ExceptionEventHandler ThrowException;
     protected virtual void OnThrowException(RAPIException e)
        {
             if (ThrowException != null )
            {
                ThrowException(e);
            }
        }
    private void InitThreadProc()
        {
             int ret = 0 ;
             int timeout = m_timeout * 4 ;
             bool infinitetimeout = (timeout < 0 );

             // check for Init event 4 times / sec
             do
            {
                 // check for abort command from Dispose()
                 if (m_killThread)
                {
                     return ;
                }

                 // see if the event is set
                ret = WaitForSingleObject(m_ri.heRapiInit, 250 );

                 if ((ret == WAIT_FAILED) || (ret == WAIT_ABANDONED))
                {
                             CeRapiUninit();
                             OnThrowException( new RAPIException( " Failed to Initialize RAPI " ));
                             return ;

               }
                if ( ! infinitetimeout)
                {
                     if (timeout -- < 0 )
                    {
                             CeRapiUninit();
                             OnThrowException( new RAPIException( " Timeout waiting for device connection " ));
                             return ;
                    }
                }
            } while (ret != WAIT_OBJECT_0);

             // check the hresult
             if (m_InitResult != 0 )
            {
                Marshal.ThrowExceptionForHR(m_InitResult);
            }

             lock ( this )
            {
                m_connected = true ;
            }

             // throw the connected event
             if (RAPIConnected != null )
            {
                RAPIConnected();
            }

             // clean up
            CloseHandle(m_hInitEvent);
        }

通过对上面代码的修改，我们定义了ExceptionEventHandler委托，那么当m_rapi初始化时: 获取连接失败的提示，给用户展示提示信息。

m_rapi.ThrowException += new ExceptionEventHandler(m_rapi_ThrowException);
void m_rapi_ThrowException(RAPIException e)
{
MessageBox.Show( " 连接超时！请确认把PDA和PC机连接好！ " );
}

上面的修改的代码中添加了CeRapiUninit()这个方法的调用，也就是说当PC和PDA没有连接时候，调用CeRapiInitEx方法，连接超时，但是资源仍然被占用，因此需要调用这个方法来释放资源。

[DllImport("rapi.dll", CharSet = CharSet.Unicode)]
internal static extern int CeRapiUninit();

曾经在项目中因没有调用这个CeRapiUninit时候，在pda和pc机没有连接:设备断开，抛出上面的异常情况给用户提示后，再将pda和pc连接，发现当pda和pc连接不成功,再一次断开，再一次连接，断开，始终都是连接不成功。最后发现问题是第一次连接设备抛出异常后没有释放资源引起的。

2、为了详细说明关于pda和pc连接状况监控，自己写了一个简单demo。做为学习的记录：

代码

   public partial class MainForm : Form
    {
         internal class MyEventArgs : EventArgs
        {
             public Control Target;
             public string Text;
             public MyEventArgs(Control target, string text)
            {
                Target = target;
                Text = text;
            }
        }

         private RAPI m_rapi = new RAPI();
         private EventHandler statusUpdate;

         public MainForm()
        {
            InitializeComponent();
            m_rapi.RAPIConnected += new RAPIConnectedHandler(m_rapi_RAPIConnected);
            m_rapi.RAPIDisconnected += new RAPIConnectedHandler(m_rapi_RAPIDisconnected);
            m_rapi.ActiveSync.Listen += new ListenHandler(ActiveSync_Listen);
            m_rapi.ActiveSync.Answer += new AnswerHandler(ActiveSync_Answer);
            m_rapi.ThrowException += new ExceptionEventHandler(m_rapi_ThrowException);
            statusUpdate = new EventHandler(StatusUpdate);
             m_rapi.Connect( false , 2 );
        }

         private void StatusUpdate( object sender, EventArgs args)
        {
            (sender as Label).Text = (args as MyEventArgs).Text;
        }

         void m_rapi_ThrowException(RAPIException e)
        {
            MessageBox.Show( " 连接超时！请确认把PDA和PC机连接好！ " );
        }

         void ActiveSync_Answer()
        {
             if ( this .label1.InvokeRequired)
            {
                 this .Invoke(statusUpdate, new object [] { this .label1, new MyEventArgs( this .label1, " 连接状态:连接中...! " ) });
            }
             else
            {
                statusUpdate( this .label1, new MyEventArgs( this .label1, " 连接状态:连接中...! " ));
            }
        }

         void ActiveSync_Listen()
        {
             if ( this .label1.InvokeRequired)
            {
                 this .Invoke(statusUpdate, new object [] { this .label1, new MyEventArgs( this .label1, " 连接状态:设备未连接! " ) });
            }
             else
            {
                statusUpdate( this .label1, new MyEventArgs( this .label1, " 连接状态:设备未连接! " ));
            }
        }

         void m_rapi_RAPIDisconnected()
        {
             if ( this .label1.InvokeRequired)
            {
                 this .Invoke(statusUpdate, new object [] { this .label1, new MyEventArgs( this .label1, " 连接状态:连接关闭! " ) });
            }
             else
            {
                statusUpdate( this .label1, new MyEventArgs( this .label1, " 连接状态:连接关闭! " ));
            }
        }

         void m_rapi_RAPIConnected()
        {
             if ( this .label1.InvokeRequired)
            {
                 this .Invoke(statusUpdate, new object [] { this .label1, new MyEventArgs( this .label1, " 连接状态:设备已连接! " ) });
            }
             else
            {
                statusUpdate( this .label1, new MyEventArgs( this .label1, " 连接状态:设备已连接! " ));
            }
        }

         private void MainForm_Load( object sender, EventArgs e)
        {

        }

         private void button1_Click( object sender, EventArgs e)
        {
             if (m_rapi.DeviceFileExists( @" \***\****.sdf " ))
            {
                MessageBox.Show( " 文件存在！连接是成功的！ " );
            }
             else
            {
                MessageBox.Show( " 文件不存在！，连接不成功！ " );
            }
        }
    }

通过demo发现，连接状态的变化过程：

1.连接pda时候：设备未连接---->连接中...----->设备已连接

2.断开pda上：设备已连接----->连接关闭------->设备未连接

Best Regards,

Charles Chen

秒客网

WinCE5.0移动平台开发笔记(OpenNETCF.Desktop.Communication连接和断开使用心得)

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