Win32 LB_GETTEXT 返回垃圾

2022-01-16 00:00:00 string winapi listbox c++

我遇到的问题很可能是一个简单的问题，但对我来说仍然是个问题.我在 Win32/C++ 中使用列表框，当从我的列表框中获取选定的文本时，返回的字符串只是垃圾.它是一个结构或类似的句柄?

I have a problem which is most likely a simple problem, but neverthe less still a problem for me. I am using the Listbox in Win32 / C++ and when getting the selected text from my listbox the string returned is just garbage. It is a handle to a struct or similar?

下面是我得到的代码和示例.

Below is the code and an example of what I get.

std::string Listbox::GetSelected() {
int index = -1;
int count = 0;

count = SendMessage(control, LB_GETSELCOUNT, 0, 0);

if(count > 0) {
    index = SendMessage(control, LB_GETSEL, 0, 0);
}

return GetString(index);
}


std::string Listbox::GetString(int index) {
int count = 0;
int length = 0;
char * text;

if(index >= 0) {
    count = GetItemCount();

    if(index < count) {
        length = SendMessage(control, LB_GETTEXTLEN, (WPARAM)index, 0);
        text = new char[length + 1];

        SendMessage(control, LB_GETTEXT, (WPARAM)index, (LPARAM)text);
    }
}
std::string s(text);
delete[] text;

return s;
}

GetItemCount 就是这样做的.它只是获取当前列表框中的项目数.

GetItemCount just does that. It just gets the number of items currently in the listbox.

我从列表框中获取的字符串是测试字符串"，它返回了 ¨±é? Tz?

The string I was grabbing from the Listbox is "Test String" and it returned ¨±é??Tz?

如有任何帮助，谢谢.

好的，我将范围缩小到我的 GetSelected 函数，因为 GetString 返回了正确的字符串.

Ok, I narrowed it down to my GetSelected function as GetString returns the correct string.

推荐答案

LB_GETSEL 消息不返回所选项目的索引，它返回您在 WPARAM 中传递的 ITEM 的所选状态.

The LB_GETSEL message does not return the index of a selected item, it returns the selected STATE of the ITEM you pass in WPARAM.

您还有一个严重的错误，如果没有选择任何项目，您将尝试检索索引 -1 处的项目字符串，这显然是错误的.检查这些 SendMessage 调用的返回值将有助于您诊断问题.

You also have a serious bug where if no items are selected you will attempt to retrieve the string of the item at index -1, which is clearly wrong. Checking the return values of these SendMessage calls would have helped you diagnose the problem.

这里是一个如何获取第一个选中项的文本的示例；

Here's an example of how to get the text of the first selected item;

// get the number of items in the box.
count = SendMessage(control, LB_GETCOUNT, 0, 0);

int iSelected = -1;

// go through the items and find the first selected one
for (int i = 0; i < count; i++)
{
  // check if this item is selected or not..
  if (SendMessage(control, LB_GETSEL, i, 0) > 0)
  {
    // yes, we only want the first selected so break.
    iSelected = i;
    break;
  }
}

// get the text of the selected item
if (iSelected != -1)
  SendMessage(control, LB_GETTEXT, (WPARAM)iSelected , (LPARAM)text);

或者，您可以使用 LB_GETSELITEMS 来获取所选项目的列表.

Alternatively you can use LB_GETSELITEMS to get a list of the items that are selected.

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