Mobile GPS Reader.docx

1、Mobile GPS Reader核心类 GPSReader/ GPSReader.cs/ Copyright (C) 2003 JW Hedgehog, Inc. All rights reserved/ JW Hedgehog, Inc/ / / Direct questions to mailto:jimw/ / This code, comments and information are provided AS IS with/ no warrenty of any kind, either expressed or implied, including/ but not limit

2、ed to the implied warranties of merchentability and/or/ fitness for a particular purpose/ -using System;using System.Data;using System.Windows.Forms ;using System.Runtime.InteropServices ;using System.Text ;using System.Collections ;using System.Threading ;using System.IO ;namespace GPSExample.Util

3、/ / Class that manages the GPS reading process. / / To get started using the class do the following / 1) Construct GPSReader passing the port name and baud rate of the GPS device / C#: GPSReader gps = new GPSReader(COM4:, 4800) ; / VB: Dim WithEvents gps As New GPSReader(COM4:, 4800) / 2) Handle the

4、 OnGPSMessage event / This event will fire each time the GPS sends an update / 3) Call gps.StartRead() / Launches the GPS reading process on a background thread / / Use the StartRead and StopRead methods to control the GPS reading process. Before calling / StartRead you must provide at least the por

5、t name in the form COMx (x is the port number) and / the baud rate. You can do this using either a constructor or the PortName and BaudRate properties. / Each time a GPS message is received, the OnGPSMessage event will fire passing an instance of the / GPSEventArgs class containing the raw GPS sente

6、nce along with some of the values already parsed into / read-only fields. / / This class does the actual GPS reading work on a background thread. The individual OnGPSMessage events / are raised in a UI thread safe manner so no special handling is required. Because it is considered unsafe / to intera

7、ct with UI elements (TextBox, ListBox, etc.) from a thread other then the thread on which they were / created, the GPS reader thread raises the OnGPSMessage event on the UI thread. These is acheived by deriving / the GPSReader class from Control and then using the inherited Invoke method. Calling th

8、is.Invoke causes the / event to be raised on the same thread on which the GPSReader was created. Since the GPSReader is usually / created as a member of either a Form or a method on a Form, it is safe to assume that the GPSReader was / created on the same thread as the Form and the Forms associated

9、UI elements. / / Because there can sometimes be a short delay between when StartRead/StopRead are called and when the / action actually occurs on the background thread, OnGPSStartRead and OnGPSStopRead events are provided. / Each fires when the background thread actually performs the action. Like th

10、e OnGPSMessage event, / these are raised in a UI thread safe manner. / / To support the broadest number of GPS devices, the class actually supports two different read modes. / The preferred read mode is MesssageMode. In MessageMode, we let the COMM port driver monitor the / GPS stream watching for t

11、he arrival of the carriage-return (n). Our code blocks until the COMM port / driver notifies us of the carriage-return, at which time we then go read the entire GPS sentence from / the COMM port driver. / The alternative read mode is CharacterMode. In CharacterMode we read the data character-by-char

12、acter / from the COMM port driver manually building the GPS sentence and watching for the carriage-return. This / mode was added because experimentation showed that some GPS devices that simulate COMM ports(i.e. the GPS / might be an expansion pack of compact flash card but appears as a COMM port to

13、 the device) do not / support letting the COMM port driver monitor for the carriage-return. / Using the PreferredReadMode property, you can set which mode the GPSReader uses If you choose MessageMode / or Auto (the default) The GPSReader class tests to see if the driver supports MessageMode and if s

14、o use it. / Otherwise it will downgrade to CharacterMode. The ActiveReadMode property indicates which read mode is / actually being used. / The code that tests for MessageMode support is in the DriverSupportsMessageMode method. Because its not / possible to test every GPS in existence there is no wa

15、y to be 100% sure that this test will always work but / on the devices tested it has been reliable. / * / Note * / If you try reading from a device and the GPSReader never returns any data, the cause may be that MessageMode / support has been falsly indicated as supported. Setting the GPSReader Pref

16、erredReadMode to ReadMode.Character / should over come the problem. The need to do this has never been observered but since its not possible to test / every GPS device the possibility always exists. / * / public class GPSReader : Control / * / Constructors / * / / Default constructor / At a minimum,

17、 will need to set the PortName and BaudRate properties before calling StartRead / public GPSReader() / / Constructor - Accepts COMM port name (COMx:) / Will need to set the BaudRate properties before calling StartRead / / public GPSReader(string portName) : this() _portName = portName ; / / Construc

18、tor - Accepts COMM port name (COMx:) and BaudRate / If default COMM port settings (NoParity, 8 bits/byte and OneStopBit) are acceptable, / can call StartRead without setting any of the configuration properties / / / public GPSReader(string portName, int baudRate) : this(portName) _baudRate = baudRat

19、e ; / / Constructor - verbose / Provides full control over all COMM port settings / / / / / / public GPSReader(string portName, int baudRate, ParitySetting parity, byte byteSize, StopBitsSetting stopBits) : this(portName, baudRate) _parity = parity ; _byteSize = byteSize ; _stopBits = stopBits ; / *

20、 / Events / * / / Fires each time a GPS message is received / public event GPSEventHandler OnGPSMessage ; / / Fires when the background thread begins the read process / public event EventHandler OnGPSReadStart ; / / Fires when the background thread exits the read process / public event EventHandler

21、OnGPSReadStop ; / * / Start/Stop Reading / * / / Initiate GPS Reading / Actual reading done on a background thread - this method returns immediatly / / Throws an error if either PortName or BaudRate not set / public void StartRead() / Verify that we know the port name and baud rate if (_baudRate = b

22、audRateNotSet | _portName = portNameNotSet) throw new ApplicationException( Must set Baud Rate & Port Name before opening the port) ; Cursor.Current = Cursors.WaitCursor ; _readData = true ; _gpsReadThread = new Thread(new ThreadStart(this.GPSReadLoop) ; _gpsReadThread.Start() ; Cursor.Current = Cur

23、sors.Default ; / / Terminate GPS Reading / Sets _readData to false which exits the underlying read loop / Also closes the COMM port which aborts any pending COMM port operations / public void StopRead() Cursor.Current = Cursors.WaitCursor ; _readData = false ; Thread.Sleep(500) ; / Give thread time

24、to finish any pending work ClosePort() ; Cursor.Current = Cursors.Default ; / * / Port Setup and configuration / * / / Set Port Name (COMx:) / public string PortName get return _portName ; set _portName = value ; / / Set Baud Rate - No Default / public int BaudRate get return _baudRate ; set _baudRa

25、te = value ; / / Set Port Parity - defaults to NoParity / public ParitySetting Parity get return _parity ; set _parity = value ; / / Set Port StopBits - defaults to OneStopBit / public StopBitsSetting StopBits get return _stopBits ; set _stopBits = value ; / / Set Port Byte Size (in bits) - defaults to 8 / public byte ByteSize get return _byteSize ; set _byt