带有条目的 GtkComboBox 导致 `gtk_entry_set_text: assertion 'text != NULL' failed`

Question

我正在尝试编写一个带有条目的组合框，其中包含带有列表存储的文本。我的代码是基于the official gtk-demo的代码

问题：

当我创建一个带有条目的组合框时，

• 所有条目都居中
• 我无法选择任何条目
• 命令行显示 gtk_entry_set_text：断言 'text != NULL' 失败

代码

下面是我如何创建组合框（目前使用硬编码开关进行测试。

if (FALSE)
    {
       // works fine
       combo = gtk_combo_box_new_with_model (model);
    }
    else
    {
       // Entries are centric
       // Cannot select entries
       // command line shows gtk_entry_set_text: assertion 'text != NULL' failed
       combo = gtk_combo_box_new_with_model_and_entry (model);
    }

完整代码

#include <gtk/gtk.h>


enum
{
  TEXT_COL,
  ICON_NAME_COL

};



static GtkTreeModel *
create_icon_store (void)
{    
  const gchar *labels[6] = {
    ("Warning"),
    ("Stop"),
    ("New"),
    ("Clear"),
    ("Open")
  };

  GtkTreeIter iter;
  GtkListStore *store;
  gint i;

  store = gtk_list_store_new (1, G_TYPE_STRING);

  for (i = 0; i < G_N_ELEMENTS (labels); i++)
    {
       gtk_list_store_append (store, &iter);
       gtk_list_store_set (store, &iter,
                           TEXT_COL, (labels[i]),
                           -1);   
    }

  return GTK_TREE_MODEL (store);
}



void create_gui(GtkContainer *container)
{
   GtkWidget *combo;
   GtkTreeModel *model;
   GtkCellRenderer *renderer;
   GtkTreeIter iter;

    model = create_icon_store ();
    if (FALSE)
    {
       // works fine
       combo = gtk_combo_box_new_with_model (model);
    }
    else
    {
       // Entries are centric
       // Cannot select entries
       // command line shows gtk_entry_set_text: assertion 'text != NULL' failed
       combo = gtk_combo_box_new_with_model_and_entry (model);
    }
    
    g_object_unref (model);
    gtk_container_add (container, combo);


    renderer = gtk_cell_renderer_text_new ();
    gtk_cell_layout_pack_start (GTK_CELL_LAYOUT (combo), renderer, TRUE);
    gtk_cell_layout_set_attributes (GTK_CELL_LAYOUT (combo), renderer,
                                    "text", TEXT_COL,
                                    NULL);

    gtk_combo_box_set_active (GTK_COMBO_BOX (combo), 0);   
    
}


/**
 *  standard stuff. Check out create_gui() 
 **/
int main(int argc, char *argv[])
{
  gtk_init (&argc, &argv);

  GtkWidget *window;
  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  GtkWidget * box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 5);
  gtk_container_add (GTK_CONTAINER (window), box);

  create_gui (GTK_CONTAINER (box));

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

  gtk_widget_show_all(window);
  gtk_main();

  return 0;
}

Answer 1

说明

1. 您需要告诉 GtkEntry（组合框的）应该使用哪一列：
   • 你可以用gtk_combo_box_set_entry_text_column
   • 您还应该指定gtk_combo_box_set_id_column（不知道为什么，但 gtk 会这样做）
2. 当您使用gtk_combo_box_set_entry_text_column 时，您不再需要自己的渲染器；否则，您将显示两列。

通用代码

这是一个函数，它将创建一个组合框，其中包含一个带有一个文本列的列表存储条目 (G_TYPE_STRING)

/**
 * Creates a combo box for list store with one text column.
 *    (= ComboBoxText)
 * The combo box will own `model`. No `g_object_unref` needed.
 */
GtkComboBox *
create_combo_box_with_entry(GtkListStore *model)
{
   GtkWidget *combo;   

   combo = gtk_combo_box_new_with_model_and_entry (GTK_TREE_MODEL (model));   
   g_object_unref (model);

   // Note: You don't need to use an a renderer, if you have 
   //      a simple ComboBox for text with an entry, because
   //      the following functions will setup a renderer     
   gtk_combo_box_set_entry_text_column (GTK_COMBO_BOX (combo), 0);
   gtk_combo_box_set_id_column (GTK_COMBO_BOX (combo), 0);

   return GTK_COMBO_BOX (combo);
}