调整对象不是小部件类型 GtkBuilder

Posted 2023-02-16

【中文标题】调整对象不是小部件类型 GtkBuilder

【英文标题】：Adjustment object not a widget type GtkBuilder

【发布时间】：2020-12-01 08:43:24

【问题描述】：

我无法使用我的林间空地文件中的Gtk::Adjustment 小部件。该程序构建并运行时出现以下错误：

(test-glade-spinbutton:227780): gtkmm-CRITICAL **: 13:38:45.769: gtkmm: object `adjustment_width' (type=`gtkmm__GtkAdjustment') (in GtkBuilder file) is not a widget type.

(test-glade-spinbutton:227780): gtkmm-CRITICAL **: 13:38:45.769: gtkmm: Gtk::Builder: widget `adjustment_width' was not found in the GtkBuilder file, or the specified part of it.

** (test-glade-spinbutton:227780): CRITICAL **: 13:38:45.769: Gtk::Builder::get_widget(): dynamic_cast<> failed.

但是，对于这篇文章，我删除了与 Gtk::Adjustment 的交互，因此程序可以实际运行。如果我尝试读取调整小部件的当前值，程序会崩溃。

以下是 C++ 代码：

#include <gtkmm.h>

using Gtk::Adjustment;
using Gtk::Application;
using Gtk::Builder;
using Gtk::Grid;
using Gtk::SpinButton;
using Gtk::Window;

class MyWindow : public Window

    Grid       *main_content;
    Adjustment *adjustment_width;
    SpinButton *width;

public:
    MyWindow()
    
        auto builder = Builder::create_from_file("test-spinbutton.glade");

        builder->get_widget("main_content"    , main_content);
        builder->get_widget("adjustment_width", adjustment_width);
        builder->get_widget("width"           , width);

        add(*main_content);

        present();
    
;

int main()

    auto app = Application::create("domain.reverse.test-spinbutton");

    MyWindow hello;

    return app->run(hello);

和林间空地文件：

<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.22.2 -->
<interface>
  <requires lib="gtk+" version="3.20"/>
  <object class="GtkAdjustment" id="adjustment_height">
    <property name="lower">1</property>
    <property name="upper">2147483647</property>
    <property name="value">1</property>
    <property name="step_increment">1</property>
    <property name="page_increment">10</property>
  </object>
  <object class="GtkAdjustment" id="adjustment_width">
    <property name="lower">1</property>
    <property name="upper">2147483647</property>
    <property name="value">1</property>
    <property name="step_increment">1</property>
    <property name="page_increment">10</property>
  </object>
  <object class="GtkGrid" id="main_content">
    <property name="visible">True</property>
    <property name="can_focus">False</property>
    <child>
      <object class="GtkLabel">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <property name="margin_left">24</property>
        <property name="margin_top">6</property>
        <property name="label" translatable="yes">Width</property>
      </object>
      <packing>
        <property name="left_attach">0</property>
        <property name="top_attach">1</property>
      </packing>
    </child>
    <child>
      <object class="GtkLabel">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <property name="margin_left">24</property>
        <property name="margin_top">6</property>
        <property name="label" translatable="yes">Height</property>
      </object>
      <packing>
        <property name="left_attach">0</property>
        <property name="top_attach">2</property>
      </packing>
    </child>
    <child>
      <object class="GtkSpinButton" id="width">
        <property name="visible">True</property>
        <property name="can_focus">True</property>
        <property name="margin_left">6</property>
        <property name="margin_top">6</property>
        <property name="hexpand">True</property>
        <property name="adjustment">adjustment_width</property>
      </object>
      <packing>
        <property name="left_attach">1</property>
        <property name="top_attach">1</property>
      </packing>
    </child>
    <child>
      <object class="GtkSpinButton" id="height">
        <property name="visible">True</property>
        <property name="can_focus">True</property>
        <property name="margin_left">6</property>
        <property name="margin_top">6</property>
        <property name="hexpand">True</property>
        <property name="adjustment">adjustment_height</property>
      </object>
      <packing>
        <property name="left_attach">1</property>
        <property name="top_attach">2</property>
      </packing>
    </child>
    <child>
      <object class="GtkLabel">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <property name="label" translatable="yes">Image Size</property>
        <attributes>
          <attribute name="weight" value="bold"/>
        </attributes>
      </object>
      <packing>
        <property name="left_attach">0</property>
        <property name="top_attach">0</property>
      </packing>
    </child>
    <child>
      <object class="GtkToggleButton" id="toggle_ratio_wh">
        <property name="label">gtk-execute</property>
        <property name="visible">True</property>
        <property name="can_focus">True</property>
        <property name="receives_default">True</property>
        <property name="margin_left">6</property>
        <property name="margin_top">6</property>
        <property name="use_stock">True</property>
        <property name="always_show_image">True</property>
      </object>
      <packing>
        <property name="left_attach">2</property>
        <property name="top_attach">1</property>
        <property name="height">2</property>
      </packing>
    </child>
    <child>
      <placeholder/>
    </child>
    <child>
      <placeholder/>
    </child>
    <style>
      <class name="dialog-main-content"/>
    </style>
  </object>
</interface>

【问题讨论】：

我能够重现您的问题，很棒的示例代码。

【参考方案1】：

错误表明adjustment_width 不是小部件，就像它的inheritance tree 建议（不像网格或旋转按钮），所以get_widget 将不起作用。您需要使用get_object。例如：

#include <iostream>
#include <gtkmm.h>

using Gtk::Adjustment;
using Gtk::Application;
using Gtk::Builder;
using Gtk::Grid;
using Gtk::SpinButton;
using Gtk::Window;

class MyWindow : public Window

    Grid       *main_content;
    SpinButton *width;
    
    Glib::RefPtr<Adjustment> adjustment_width;

public:
    MyWindow()
    
        auto builder = Builder::create_from_file("test-spinbutton.glade");

        // Widgets:
        builder->get_widget("main_content"    , main_content);
        builder->get_widget("width"           , width);

        // Other objects (non widgets):

        // 1. Get the object from the object three:
        Glib::RefPtr<Glib::Object> adjustmentObject = builder->get_object("adjustment_width");

        // 2. At this point, it is a Glib::Object (which is Adjustment's base type), so we need
        //    to cast:
        adjustment_width = Glib::RefPtr<Adjustment>::cast_dynamic(adjustmentObject);

        // 3. Then we can access it normally:
        std::cout << "The adjustment value is : " << adjustment_width->get_value() << std::endl;

        add(*main_content);

        present();
    
;

int main()

    auto app = Application::create("domain.reverse.test-spinbutton");

    MyWindow hello;

    return app->run(hello);

【讨论】：

下面的所有小部件都以 <object> 标记开头，包括 Gtk::Adjustment... 所以警告消息没有在我的脑海中响起正确的铃声 LOL。谢谢你的回答:)

没问题。你是对的，这是误导。