Question

VB中FindWindow()函数的用法

Option Explicit

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

Private Sub Timer1_Timer()
Dim title As String
Dim titlelen As Long
Dim resule As Long
title = String$(256, "!")
resule = FindWindow(vbNullString, vbNullString)
titlelen = Len(title) + 1
GetWindowText resule, title, titlelen
Print title
End Sub

为什么这样子我不能的到任意窗体的名字啊？
（timer1的时间为500毫秒）

Answer 1

VB中findwindow（）函数使用：
VB声明
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
说明
寻找窗口列表中第一个符合指定条件的顶级窗口（在vb里使用：FindWindow最常见的一个用途是获得ThunderRTMain类的隐藏窗口的句柄；该类是所有运行中vb执行程序的一部分。获得句柄后，可用api函数GetWindowText取得这个窗口的名称；该名也是应用程序的标题）
返回值
Long，找到窗口的句柄。如未找到相符窗口，则返回零。会设置GetLastError
参数表
参数 类型及说明
lpClassName String，指向包含了窗口类名的空中止（C语言）字串的指针；或设为零，表示接收任何类
lpWindowName String，指向包含了窗口文本（或标签）的空中止（C语言）字串的指针；或设为零，表示接收任何窗口标题
注解
很少要求同时按类与窗口名搜索。为向自己不准备参数传递一个零，最简便的办法是传递vbNullString常数

示例
Dim hw&, cnt&
Dim rttitle As String * 256
hw& = FindWindow("ThunderRT5Main", vbNullString) ' ThunderRTMain under VB4
cnt = GetWindowText(hw&, rttitle, 255)
MsgBox Left$(rttitle, cnt), 0, "RTMain title"

Answer 2

Option Explicit

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

Private Sub Timer1_Timer()
Cls
Dim Title As String * 256
Dim Titlelen As Long
Dim Resule As Long
Resule = FindWindow(vbNullString, vbNullString)
Titlelen = 255
GetWindowText Resule, Title, Titlelen
Print Title
End Sub