当 Gtk.ComboBox 中的活动项更改时更新 Gtk.Label

如何解决当 Gtk.ComboBox 中的活动项更改时更新 Gtk.Label

我想在 Gtk.ComboBox 中的活动项发生更改时更新标签。

这就是我创建组合框的方式

public class Epoch.CitiesChooser : Gtk.Grid {
    string[] cities = {"Guwahati","Paris","London","New York"};
    
    public Gtk.ComboBox city1Box;
    public Gtk.ComboBox city2Box;
    public Gtk.ComboBox city3Box;
    public Gtk.ComboBox city4Box;
    
    enum Column {
        CITY
    }
    
    construct {
        var liststore = new Gtk.ListStore (1,typeof (string));
        
        for (int i = 0; i < cities.length; i++) {
            Gtk.TreeIter iter;
            liststore.append (out iter);
            liststore.set (iter,Column.CITY,cities[i]);
        }
        
        city1Box = new Gtk.ComboBox.with_model (liststore);
        var cell1 = new Gtk.CellRendererText ();
        city1Box.pack_start (cell1,false);
        city1Box.set_attributes (cell1,"text",Column.CITY);
            
        city1Box.set_active (0);
        
        var city2Box = new Gtk.ComboBox.with_model (liststore);
        var cell2 = new Gtk.CellRendererText ();
        city2Box.pack_start (cell2,false);
        city2Box.set_attributes (cell2,Column.CITY);
        
        city2Box.set_active (1);
        
        var city3Box = new Gtk.ComboBox.with_model (liststore);
        var cell3 = new Gtk.CellRendererText ();
        city3Box.pack_start (cell3,false);
        city3Box.set_attributes (cell3,Column.CITY);
        
        city3Box.set_active (2);
        
        var city4Box = new Gtk.ComboBox.with_model (liststore);
        var cell4 = new Gtk.CellRendererText ();
        city4Box.pack_start (cell4,false);
        city4Box.set_attributes (cell4,Column.CITY);
        
        city4Box.set_active (3);
        
        this.attach (city1Box,0);
        this.attach (city2Box,1);
        this.attach (city3Box,2);
        this.attach (city4Box,3);   
    }
}

这就是我创建标签并尝试更新它们的方式：

public class Epoch.LabelsGrid : Object {
    public Gtk.Label face1_label;
    public Gtk.Label face2_label;
    public Gtk.Label face3_label;
    public Gtk.Label face4_label;
    
    // public Epoch.CitiesChooser cities_chooser;
    
    construct {
        face1_label = new Gtk.Label ("");
        face1_label.set_markup ("<span font_desc='Inter 14'><b>Guwahati</b></span>");
        face1_label.halign = Gtk.Align.CENTER;
        face1_label.hexpand = true;
        face1_label.margin_top = 6;
        face1_label.set_ellipsize (END);
        face1_label.set_max_width_chars (12);
        
        face2_label = new Gtk.Label ("");
        face2_label.set_markup ("<span font_desc='Inter 14'><b>Paris</b></span>");
        face2_label.halign = Gtk.Align.CENTER;
        face2_label.hexpand = true;
        face2_label.margin_top = 6;
        face2_label.set_ellipsize (END);
        face2_label.set_max_width_chars (12);
        
        face3_label = new Gtk.Label ("");
        face3_label.set_markup ("<span font_desc='Inter 14'><b>London</b></span>");
        face3_label.halign = Gtk.Align.CENTER;
        face3_label.hexpand = true;
        face3_label.margin_top = 6;
        face3_label.set_ellipsize (END);
        face3_label.set_max_width_chars (12);
        
        face4_label = new Gtk.Label ("");
        face4_label.set_markup ("<span font_desc='Inter 14'><b>New York</b></span>");
        face4_label.halign = Gtk.Align.CENTER;
        face4_label.hexpand = true;
        face4_label.margin_top = 6;
        face4_label.set_ellipsize (END);
        face4_label.set_max_width_chars (12);
        
        var cities_chooser = new Epoch.CitiesChooser ();
        
        cities_chooser.city1Box.changed.connect (() => {
            face1_label.set_markup ("<span font_desc='Inter 14'><b>Paris</b></span>");
            stdout.printf ("Signal is working correctly");
        });
    }
}

应用程序编译时没有任何错误，但当组合框 (city1Box) 中的活动项发生更改时，标签不会更新。

谁能告诉我如何正确更新标签？

我认为与信号有关

解决方法

您要更改哪个 CitiesChooser 的组合框？它不能与您要连接的 CitiesChooser 相同，因为它是一个局部变量，您永远不会对它做任何事情。超出范围将被删除。

您需要连接到您 UI 中的 CitiesChooser 的信号。