PostMessage与SendMessage的区别
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PostMessage只负责将消息放到消息队列中,不确定何时及是否处理 SendMessage要等到受到消息处理的返回码(DWord类型)后才继续 PostMessage执行后马上返回 SendMessage必须等到消息被处理后才会返回。 下面通过一个小例子来说明下这2个方法进行参数传递的不同点:
//Win32 API 类 using System; using System.Runtime.InteropServices; namespace TestHwnd { public class Win32API { [DllImport("User32.dll", EntryPoint = "FindWindow")] public static extern IntPtr FindWindow(string lpClassName, string lpWindowName); [DllImport("User32.dll", EntryPoint = "FindWindowEx")] public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpClassName, string lpWindowName); /// <summary> /// 自定义的结构 /// </summary> public struct My_lParam { public int i; public string s; } /// <summary> /// 使用COPYDATASTRUCT来传递字符串 /// </summary> [StructLayout(LayoutKind.Sequential)] public struct COPYDATASTRUCT { public IntPtr dwData; public int cbData; [MarshalAs(UnmanagedType.LPStr)] public string lpData; } //消息发送API [DllImport("User32.dll", EntryPoint = "SendMessage")] public static extern int SendMessage( IntPtr hWnd, // 信息发往的窗口的句柄 int Msg, // 消息ID int wParam, // 参数1 int lParam //参数2 ); //消息发送API [DllImport("User32.dll", EntryPoint = "SendMessage")] public static extern int SendMessage( IntPtr hWnd, // 信息发往的窗口的句柄 int Msg, // 消息ID int wParam, // 参数1 ref My_lParam lParam //参数2 ); //消息发送API [DllImport("User32.dll", EntryPoint = "SendMessage")] public static extern int SendMessage( IntPtr hWnd, // 信息发往的窗口的句柄 int Msg, // 消息ID int wParam, // 参数1 ref COPYDATASTRUCT lParam //参数2 ); //消息发送API [DllImport("User32.dll", EntryPoint = "PostMessage")] public static extern int PostMessage( IntPtr hWnd, // 信息发往的窗口的句柄 int Msg, // 消息ID int wParam, // 参数1 int lParam // 参数2 ); //消息发送API [DllImport("User32.dll", EntryPoint = "PostMessage")] public static extern int PostMessage( IntPtr hWnd, // 信息发往的窗口的句柄 int Msg, // 消息ID int wParam, // 参数1 ref My_lParam lParam //参数2 ); //异步消息发送API [DllImport("User32.dll", EntryPoint = "PostMessage")] public static extern int PostMessage( IntPtr hWnd, // 信息发往的窗口的句柄 int Msg, // 消息ID int wParam, // 参数1 ref COPYDATASTRUCT lParam // 参数2 ); } } //主窗体,发送消息 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.Runtime.InteropServices; namespace TestHwnd { public partial class Main : Form { public IntPtr hwndTest; public int IwndTest; public IntPtr hwndfrmTest; public Main() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { Test test = new Test(); test.Show(this); } private void timer1_Tick(object sender, EventArgs e) { string strTest = "25425"; Win32API.COPYDATASTRUCT cds; cds.dwData = (IntPtr)100; cds.lpData = strTest; byte[] sarr = System.Text.Encoding.UTF8.GetBytes(strTest); int len = sarr.Length; cds.cbData = len + 1; Win32API.My_lParam lp=new Win32API.My_lParam(); lp.i=3; lp.s="test"; if(hwndTest!=(IntPtr)0) { if (DateTime.Now.Second % 2 == 0) { Win32API.SendMessage(hwndTest, 0x60, 1, 3);//传递2个整型参数成功 } if(DateTime.Now.Second % 3 == 0) { Win32API.SendMessage(hwndTest, 0x61, 5, ref lp);//传递整型参数和结构类型成功,这个方法加以改变后可以传递对象 } if(DateTime.Now.Second % 5 == 0) { Win32API.SendMessage(hwndTest, 0x62, 5, ref cds);//传递整型参数和不定长的字符串成功 } if(DateTime.Now.Second % 7 == 0) { Win32API.PostMessage(hwndTest, 0x63, 5, 6);//传递2个整型参数成功 } if(DateTime.Now.Second % 9 == 0) { Win32API.PostMessage(hwndTest, 0x64, 3, ref lp);//传递整型参数成功,但是传递参数lp失败,3可以传递成功。 } if(DateTime.Now.Second % 11 == 0) { Win32API.PostMessage(hwndTest, 0x65, 3, ref cds);//传递整型参数成功,传递参数cds失败,3可以传递成功。 } } } } } //子窗体接收消息以及参数 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.Runtime.InteropServices; namespace TestHwnd { public partial class Test : Form { Main main; public Test() { InitializeComponent(); } private void Test_Load(object sender, EventArgs e) { main = this.Owner as Main; main.hwndTest = this.Handle; } ///重写窗体的消息处理函数DefWndProc,从中加入自己定义消息的检测的处理入口 protected override void DefWndProc(ref Message m) { switch (m.Msg) { //接收自定义消息MYMESSAGE,并显示其参数 case 0x60: { label1.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + m.LParam.ToInt32().ToString(); } break; case 0x61: { Win32API.My_lParam ml = new Win32API.My_lParam(); Type t = ml.GetType(); ml = (Win32API.My_lParam)m.GetLParam(t); label2.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + ml.i.ToString()+":"+ml.s; } break; case 0x62: { Win32API.COPYDATASTRUCT mystr = new Win32API.COPYDATASTRUCT(); Type mytype = mystr.GetType(); mystr = (Win32API.COPYDATASTRUCT)m.GetLParam(mytype); string str2 = mystr.lpData; label3.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + str2; } break; case 0x63: { label4.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + m.LParam.ToInt32().ToString(); } break; case 0x64: { Win32API.My_lParam ml = new Win32API.My_lParam(); Type t = ml.GetType(); ml = (Win32API.My_lParam)m.GetLParam(t); label5.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + ml.i.ToString()+":"+ml.s; } break; case 0x65: { Win32API.COPYDATASTRUCT mystr = new Win32API.COPYDATASTRUCT(); Type mytype = mystr.GetType(); mystr = (Win32API.COPYDATASTRUCT)m.GetLParam(mytype); string str2 = mystr.lpData; label6.Text = DateTime.Now.ToString() + "-" + m.WParam.ToInt32().ToString() + "-" + str2; } break; default: base.DefWndProc(ref m); break; } } private void button1_Click(object sender, EventArgs e) { main.hwndTest = (IntPtr) (0); this.Close(); } } }
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