Imgui create a new window

Question

Use the following code on the main window to create a new child window

But the new window disappears immediately

bool show_dialog = true;

ImGui::SetNextWindowSize(ImVec2(400, 200));

ImGui::SetNextWindowPos(ImVec2(100, 100)); // Set the position of the new window

ImGui::Begin("Dialogx1", &show_dialog, ImGuiWindowFlags_NoCollapse);

ImGui::End();

the new window disappears not immediately