C++实现TreeView，不用其他的API，纯代码

实现一个TreeView可以使用C++的Win32 API来完成，以下是一个简单的示例代码：

#include <Windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASS wc = { 0 };
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInstance;
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszClassName = L"TreeViewExample";
    RegisterClass(&wc);

    HWND hWnd = CreateWindow(L"TreeViewExample", L"TreeView Example", WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 500, 300, nullptr, nullptr, hInstance, nullptr);

    if (!hWnd)
        return FALSE;

    ShowWindow(hWnd, nCmdShow);

    MSG msg = { 0 };
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return (int)msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HWND hTreeView;
    switch (message)
    {
    case WM_CREATE:
        hTreeView = CreateWindow(WC_TREEVIEW, L"", WS_VISIBLE | WS_CHILD | WS_BORDER | TVS_HASBUTTONS | TVS_HASLINES | TVS_LINESATROOT,
            0, 0, 200, 200, hWnd, nullptr, ((LPCREATESTRUCT)lParam)->hInstance, nullptr);

        TVINSERTSTRUCT tvInsert;
        tvInsert.hParent = nullptr;
        tvInsert.hInsertAfter = TVI_ROOT;
        tvInsert.item.mask = TVIF_TEXT;
        tvInsert.item.pszText = L"Item 1";
        HTREEITEM hItem1 = (HTREEITEM)SendMessage(hTreeView, TVM_INSERTITEM, 0, (LPARAM)&tvInsert);

        tvInsert.hParent = hItem1;
        tvInsert.item.pszText = L"Item 2";
        HTREEITEM hItem2 = (HTREEITEM)SendMessage(hTreeView, TVM_INSERTITEM, 0, (LPARAM)&tvInsert);

        tvInsert.hParent = hItem2;
        tvInsert.item.pszText = L"Item 3";
        SendMessage(hTreeView, TVM_INSERTITEM, 0, (LPARAM)&tvInsert);

        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

在上述代码中，我们首先创建了一个窗口，然后在窗口创建的过程中创建了一个TreeView控件。我们使用`TVM_INSERTITEM`消息向TreeView控件中插入了三个节点，并将它们分别命名为"Item 1"、"Item 2"和"Item 3"。

当然，这只是一个简单的示例代码，你可以根据自己的需求来定制TreeView的外观和功能。