错误:无效值不应该被忽略-C/GTK + [英] error: void value not ignored as it ought to be - C/GTK+

问题描述

我正在尝试在GTK +中创建一个具有如下所示标签的窗口:

I am trying to create a window in GTK+ that has tab looks like this:

每当用户单击新建"按钮时，就会出现一个新标签.

Whenever the user clicks in the "New" button, there is a new tab appear.

但是，当我编译程序时，出现了错误:void值不应该被忽略

However, when I was compiling my program I got an error: void value not ignored as it ought to be

phongcao@phongcao:~$ g++ /home/phongcao/C++/GTK+/newtab.cc -o /home/phongcao/C++/GTK+/newtab `pkg-config gtk+-2.0 --cflags --libs`
/home/phongcao/C++/GTK+/newtab.cc: In function ‘int main(int, char**)’:
/home/phongcao/C++/GTK+/newtab.cc:51:3: error: void value not ignored as it ought to be

这是代码:

#include <gtk/gtk.h>

void destroy(GtkWidget *window, gpointer data) {
  gtk_main_quit();
}

void new_tab(GtkNotebook *notebook, GtkWidget *content, GtkWidget *hbox) {
  gtk_notebook_append_page(notebook, content, hbox);
}

int main(int argc, char *argv[]) 
{
  GtkWidget *window, *label, *content;
  GtkWidget *button, *hbox, *notebook;

  gtk_init(&argc, &argv);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  gtk_container_set_border_width(GTK_CONTAINER(window), 10);
  gtk_window_set_title(GTK_WINDOW(window), "New Tab");
  gtk_widget_set_size_request(window, 300, 200);

  notebook = gtk_notebook_new();

  button = gtk_button_new_with_label("New");
  label = gtk_label_new("Tab");
  hbox = gtk_hbox_new(FALSE, 5);
  content = gtk_label_new("This is a tab");
  gint a = 0;

  gtk_box_pack_start_defaults(GTK_BOX(hbox), label);
  gtk_box_pack_start_defaults(GTK_BOX(hbox), button);

  gtk_notebook_append_page(GTK_NOTEBOOK(notebook), content, hbox);
  gtk_notebook_set_tab_pos(GTK_NOTEBOOK(notebook), GTK_POS_TOP);

  //This following line is where the error is from:
  g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), NULL); 

  g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(destroy), NULL);

  gtk_container_add(GTK_CONTAINER(window), notebook);

  gtk_widget_show_all(hbox); 
  gtk_widget_show_all(window);

  gtk_main();
  return 0;
}

感谢您的帮助！！我真的很感激！

推荐答案

行号对我来说意义不大，但我认为您的问题就在这里(出于说明目的而重新格式化):

The line number doesn't make much sense to me but I think your problem is right here (reformatted for illustrative purposes):

g_signal_connect(G_OBJECT(button), "new_tab",
    G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), /* <== Badness */
    NULL
);

您正在G_CALLBACK宏内调用new_tab函数. new_tab函数返回void(即没有返回值)，但是在需要一个值的上下文中被调用，因此将出现无效的空值"错误.我想你的意思是说更多这样的话:

You're calling the new_tab function inside the G_CALLBACK macro. The new_tab function returns void (i.e. no return value) but it is being called in a context that needs a value and hence the "void value not ignored" error. I think you mean to say something more like this:

g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab), NULL);

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