如何获取控制文本？

Question

I want to get control text. but this code return parent class name.

const wchar_t* textInput = L"Login";   

HWND btnHandle = CreateWindowEx(0, L"BUTTON", textInput, WS_CHILD | WS_VISIBLE | BS_DEFPUSHBUTTON,
                 mCoordinate.x, mCoordinate.y, mDimension.cx, mDimension.cy, parentHandle, NULL, 
                 (HINSTANCE)GetWindowLongPtr(parentHandle, GWLP_HINSTANCE), NULL);

wchar_t* textOutput;
int length = GetWindowTextLengthW(btnHandle);
GetWindowText(btnHandle, textOutput, length);

MessageBox(NULL, textOutput, L"Window Text", MB_OK);

Answer 1

As documented, the lpString argument to GetWindowTextW is:

The buffer that will receive the text.

The API does not provide that buffer for you. Instead, you will have to pass it in, as illustrated here:

size_t length{ GetWindowTextLengthW(btnHandle) };
// Allocates a buffer for `length` characters plus a NUL terminator
std::wstring text(length, L'\0');
// The API promises to write a NUL terminator into the final character
// so it is safe to lie about the length
length = GetWindowTextW(btnHandle, text.data(), text.size() + 1);
// Resize in case we got less than promised
text.resize(length);

MessageBoxW(NULL, text.c_str(), L"Window Text", MB_OK);