不知道如何正确使用IShellWindows :: Item [英] don't know how to use IShellWindows::Item correctly

问题描述

我在XP系统上使用VC6。

I'm using VC6 on XP system.

以下是我的代码。它在我的计算机上运行完美，但在其他计算机上，似乎pisw-> Item（v，&pidisp）不等于S_OK。现在我想弄清楚这里有什么错误

The following is my code. It runs perfectly on my computer, but on other computers it seems that pisw->Item(v, &pidisp) doesn't equals to S_OK. Now I'm trying to figure out what's wrong here

  IShellWindows *pisw;
  if (SUCCEEDED(CoCreateInstance(CLSID_ShellWindows, NULL, CLSCTX_ALL,
                             IID_IShellWindows, (void**)&pisw))) {
  VARIANT v;
  V_VT(&v) = VT_I4;
  IDispatch  *pidisp;
  found = FALSE;

  for (V_I4(&v) = 0; !found && pisw->Item(v, &pidisp) == S_OK; V_I4(&v)++) {
     IWebBrowserApp *piwba;
    if (SUCCEEDED(pidisp->QueryInterface(IID_IWebBrowserApp, (void**)&piwba))) {
               //  blablabla....do something..
  }

所以我改变了一些代码到

So I changed some code to

...
IDispatch *pidisp;
hr = pisw->Item(v, &pidisp);
if (SUCCEEDED(hr))
{
      for (V_I4(&v) = 0; !found ; V_I4(&v)++) {
     IWebBrowserApp *piwba;
     if (SUCCEEDED(pidisp->QueryInterface(IID_IWebBrowserApp, (void**)&piwba))) {
               //  blablabla....do something..
   }

}

到1.当运行到pidisp-> ..步骤时，它获取访问冲突错误。

then the return value of hr becomes to 1. And it gets access violation errors when running to "pidisp->.." step. Can anyone help me?

推荐答案

原始代码错误地测试了 pisw-> Item v，& pidisp）。

The original code incorrectly tests the result of pisw->Item(v, &pidisp). Weird, because it does use the correct check later on.

问题是，除了 S_OK 。您的修正是正确的，您应该使用 SUCCEEDED（hr），但您错误地将循环移到 SUCCEEDED（hr）测试。对于 V_I4（& v）的每个值，应检查 SUCCEEDED（hr）。

The problem is that there are many success return values besides S_OK. Your fix is correct, you should use SUCCEEDED(hr), but you incorrectly moved the loop INSIDE the SUCCEEDED(hr) test. You should check SUCCEEDED(hr) for every value of V_I4(&v).

您的 S_FALSE 结果是因为您现在呼叫 hr = pisw-> Item v，& pidisp）; 之前的循环，这意味着 v 是未初始化的（垃圾）。假设它的垃圾值为728365. S_FALSE 意味着：调用成功，但有不到728365窗口。

Your S_FALSE result is because you now call hr = pisw->Item(v, &pidisp); before the loop, which means v is uninitialized (garbage). Assume for a moment that its garbage value is 728365. S_FALSE means: the call succeeded, but there are less than 728365 windows.

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