[英]error: void value not ignored as it ought to be - C/GTK+
I am trying to create a window in GTK+ that has tab looks like this: 我正在尝试在GTK +中创建一个具有选项卡的窗口,如下所示:
Whenever the user clicks in the "New" button, there is a new tab appear. 每当用户单击“新建”按钮时,就会出现一个新选项卡。
However, when I was compiling my program I got an error: void value not ignored as it ought to be 但是,当我编译程序时,出现一个错误:void值不应该被忽略,因为它应该是
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
And here is the code: 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;
}
Thanks for your help!! 谢谢你的帮助!! I really appreciate it!!
我真的很感激!!
The line number doesn't make much sense to me but I think your problem is right here (reformatted for illustrative purposes): 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):
g_signal_connect(G_OBJECT(button), "new_tab",
G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), /* <== Badness */
NULL
);
You're calling the new_tab
function inside the G_CALLBACK
macro. 您正在
G_CALLBACK
宏中调用new_tab
函数。 The new_tab
function returns void
(ie no return value) but it is being called in a context that needs a value and hence the "void value not ignored" error. 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调用它,因此出现“无效值不被忽略”错误。 I think you mean to say something more like this: 我认为您的意思是说更多这样的话:
g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab), NULL);
g_signal_connect(G_OBJECT(button), "new_tab", G_CALLBACK(new_tab(GTK_NOTEBOOK(notebook), content, hbox)), NULL);
Are you sure you want to pass parameters to new_tab()
? 您确定要将参数传递给
new_tab()
吗? Simply put G_CALLBACK(new_tab)
. 只需放入
G_CALLBACK(new_tab)
。 That will resolve error. 这样可以解决错误。
If you want to call "new_tab" then you have to call the function explicitly at proper place (say before passing to G_CALLBACK
). 如果要调用“ new_tab”,则必须在适当的位置显式调用该函数(例如,传递给
G_CALLBACK
之前)。
For your query you can refer to this small tutorial . 对于您的查询,您可以参考此小型教程 。
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