如何让一个已经打开的系统获得焦点

[gengxin_914]

A和B是两个独立的系统，如果这时B系统已经打开，但可能已经最小化了，这时在A系统中如何才能让B系统获得焦点显示到最前面来呢

[cuike519]

This function brings the specified window to the top of the z-order. If the window is a top-level window, it is activated. If the window is a child window, the top-level parent window associated with the child window is activated.

BOOL BringWindowToTop(
HWND hWnd
);

[zgke]

先要获取你想要窗体的句柄

你可以使用

[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

然后使用

[DllImport("User32.dll", CharSet = CharSet.Auto)]
public static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
让窗体最大化

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern bool SetForegroundWindow(IntPtr hWnd);
记活窗体..

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SetFocus(IntPtr hWnd);
设置焦点

[冷月孤峰]

完整的：

using   System;  
  using   System.Drawing;  
  using   System.Collections;  
  using   System.ComponentModel;  
  using   System.Windows.Forms;  
  using   System.Data;  
  using   System.Diagnostics;  
  using   System.Reflection;  
  using   System.Runtime.InteropServices;  
   
  public   class   MainForm   :   System.Windows.Forms.Form  
  {  
      private   const   int   WS_SHOWNORMAL   =   1;  
  [DllImport("User32.dll")]  
  private   static   extern   bool   ShowWindowAsync(IntPtr   hWnd,   int   cmdShow);  
  [DllImport("User32.dll")]    
  private   static   extern   bool   SetForegroundWindow(IntPtr   hWnd);  
   
  public   MainForm()  
  {  
  InitializeComponent();  
  }  
  ///   <summary>  
  ///   应用程序的主入口点。  
  ///   </summary>  
  [STAThread]  
  static   void   Main()    
  {  
  Process   instance   =   GetRunningInstance();  
  if(instance   ==   null)  
  {  
  Application.Run(new   MainForm());  
  }  
  else  
  {  
  HandleRunningInstance(instance);  
  }  
  }  
  ///   <summary>  
  ///   获取应用程序的实例,没有其它的例程，返回Null  
  ///   </summary>  
  ///   <returns></returns>  
  public   static   Process   GetRunningInstance()  
  {  
  Process   current   =   Process.GetCurrentProcess();  
  Process[]   processes   =   Process.GetProcessesByName   (current.ProcessName);  
  //遍历正在有相同名字运行的例程  
  foreach   (Process   process   in   processes)  
  {  
  //忽略现有的例程  
  if   (process.Id   !=   current.Id)  
  //确保例程从EXE文件运行  
  if   (Assembly.GetExecutingAssembly().Location.Replace("/",   "\\")   ==   current.MainModule.FileName)  
  //返回另一个例程实例  
  return   process;  
  }  
  return   null;  
  }  
  ///   <summary>  
  ///   获取窗口句柄  
  ///   </summary>  
  ///   <param   name="instance"></param>  
  public   static   void   HandleRunningInstance(Process   instance)  
  {  
  //确保窗口没有被最小化或最大化  
  ShowWindowAsync   (instance.MainWindowHandle   ,   WS_SHOWNORMAL);  
  //设置真实例程为foreground   window  
  SetForegroundWindow   (instance.MainWindowHandle);  
  }  
  }

[LemIST]

[Quote=引用 3 楼 wf5360308 的回复:]
完整的：

C# code
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;

public class MainForm : System.Windows.Forms.Form
{
private…
[/Quote]
学习

[csrwgs]

上面贴代码的好恐怖。

用FindWindows（）函数获取窗口的Handle。

用GetWindowsLong和SetWindowsLong设置窗口的状态

用SetWindowsPos刷新窗口状态。

楼主请看：
http://hi.baidu.com/csrwgs/blog/item/d0f92912ca7012d8f7039e13.html

http://hi.baidu.com/csrwgs/blog/item/33f88d7204acc3148701b0fc.html

[simen_frankly]

学习了