单选按钮与复选按钮相似,只是单选按钮是分组的,在一组中只有一个处于选中/按下状态。这在你的应用程序中要从几个选项中选一个的地方可以用到。
用这些调用之一来创建一个新的单选按钮:
GtkWidget *gtk_radio_button_new( GSList *group ); GtkWidget *gtk_radio_button_new_from_widget( GtkRadioButton *group ); GtkWidget *gtk_radio_button_new_with_label( GSList *group, const gchar *label ); GtkWidget* gtk_radio_button_new_with_label_from_widget( GtkRadioButton *group, const gchar *label ); GtkWidget *gtk_radio_button_new_with_mnemonic( GSList *group, const gchar *label ); GtkWidget *gtk_radio_button_new_with_mnemonic_from_widget( GtkRadioButton *group, const gchar *label ); |
你可能注意到了,这些调用有个额外的参数。它们需要一个组以正常运作。第一次调用 gtk_radio_button_new() 或 gtk_radio_button_new_with_label() 应该传递 NULL 值作为第一个参数。接着用如下函数创建一个组:
GSList *gtk_radio_button_get_group( GtkRadioButton *radio_button ); |
有一点很重要,必须为每个添加到组的新按钮调用 gtk_radio_button_get_group(),并把前一个按钮作为参数。返回的结果再传给下一个调用 gtk_radio_button_new() 或 gtk_radio_button_new_with_label()。这样才能建立连锁的按钮。看一下下面的示例会更清楚一些。
你可以使用下面的语法来稍微缩短上面的步骤,它不需要一个变量来存储按钮列表:
button2 = gtk_radio_button_new_with_label( gtk_radio_button_get_group (GTK_RADIO_BUTTON (button1)), "button2"); |
而 _from_widget() 创建函数可以让你做得更简洁些,它完全省略了 gtk_radio_button_get_group() 调用。在下面示例的第三个按钮就是用这种方法创建的。
button2 = gtk_radio_button_new_with_label_from_widget( GTK_RADIO_BUTTON (button1), "button2"); |
明确地指定哪个按钮应该被默认按下也是个好主意,用:
void gtk_toggle_button_set_active( GtkToggleButton *toggle_button, gboolean state ); |
这在开关按钮部分描述过,在这里它也确切地以同样的方式工作。多个单选按钮组合到一起后,组中一次只能有一个被激活。如果用户点击一个单选按钮,接着点另一个,第一个单选按钮会首先发出 "toggled" 信号 (以报告变得不激活了),然后第二个也会发出 "toggled" 信号 (以报告变得激活了)。
下面的示例创建一个含三个按钮的单选按钮组。
#include <glib.h> #include <gtk/gtk.h> gint close_application( GtkWidget *widget, GdkEvent *event, gpointer data ) { gtk_main_quit (); return FALSE; } int main( int argc, char *argv[] ) { GtkWidget *window = NULL; GtkWidget *box1; GtkWidget *box2; GtkWidget *button; GtkWidget *separator; GSList *group; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); g_signal_connect (G_OBJECT (window), "delete_event", G_CALLBACK (close_application), NULL); gtk_window_set_title (GTK_WINDOW (window), "radio buttons"); gtk_container_set_border_width (GTK_CONTAINER (window), 0); box1 = gtk_vbox_new (FALSE, 0); gtk_container_add (GTK_CONTAINER (window), box1); gtk_widget_show (box1); box2 = gtk_vbox_new (FALSE, 10); gtk_container_set_border_width (GTK_CONTAINER (box2), 10); gtk_box_pack_start (GTK_BOX (box1), box2, TRUE, TRUE, 0); gtk_widget_show (box2); button = gtk_radio_button_new_with_label (NULL, "button1"); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); gtk_widget_show (button); group = gtk_radio_button_get_group (GTK_RADIO_BUTTON (button)); button = gtk_radio_button_new_with_label (group, "button2"); gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (button), TRUE); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); gtk_widget_show (button); button = gtk_radio_button_new_with_label_from_widget (GTK_RADIO_BUTTON (button), "button3"); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); gtk_widget_show (button); separator = gtk_hseparator_new (); gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 0); gtk_widget_show (separator); box2 = gtk_vbox_new (FALSE, 10); gtk_container_set_border_width (GTK_CONTAINER (box2), 10); gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, TRUE, 0); gtk_widget_show (box2); button = gtk_button_new_with_label ("close"); g_signal_connect_swapped (G_OBJECT (button), "clicked", G_CALLBACK (close_application), window); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); GTK_WIDGET_SET_FLAGS (button, GTK_CAN_DEFAULT); gtk_widget_grab_default (button); gtk_widget_show (button); gtk_widget_show (window); gtk_main (); return 0; } |