Question

我正在尝试在构造函数中的类中分配一个GtkWidget指针，但是我遇到了运行时错误。

#include <gtk/gtk.h>

class MainWindowController
{
private:
  GtkWidget * appWindow;
  const gchar * windowTitle = "Window title";
public:
  MainWindowController(GtkApplication * app);
  ~MainWindowController();
  void show();
};

MainWindowController::MainWindowController(GtkApplication* app)
{
  //this works
  GtkWidget* window = gtk_application_window_new(app);

  //not this 
  //appWindow = gtk_application_window_new(app);

  /*adding it into the init list does not work either... I have tried
   MainWindowController::MainWindowController(GtkApplication* app)
      :appWindow(gtk_application_window_new(app)) {}
  */

  gtk_window_set_title(GTK_WINDOW(appWindow), windowTitle);
  gtk_window_set_default_size(GTK_WINDOW(appWindow), 500, 500);
}

终端报告了以下错误：

(main:156): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer
(main:156): GLib-GObject-CRITICAL **: g_signal_handlers_destroy: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(main:156): GLib-GObject-WARNING **: instance with invalid (NULL) class pointer
(main:156): GLib-GObject-CRITICAL **: g_signal_handlers_destroy: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

为什么这不会导致错误

GtkWidget* window = gtk_application_window_new(app);

但是这样做了？

appWindow = gtk_application_window_new(app);

更新：这是我的main.cpp

#include <gtk/gtk.h>
#include "mainWindowController.hpp"

static void
activate (GtkApplication* app,
          gpointer        user_data)
{
  MainWindowController mainController(app);
}

int
main (int    argc,
      char **argv)
{
  GtkApplication *app;
  int status;

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  status = g_application_run (G_APPLICATION (app), 0, 0);
  g_object_unref (app);

  return status;
}

我也在编译：g ++ pkg-config --cflags gtk+-3.0 -o main main.cpp pkg-config --libs gtk+-3.0 -std = c ++ 0x

Answer 1

您没有显示完整的代码，但我认为问题出在这一行：

MainWindowController mainController(app);

在这里，您创建一个mainController类型的局部变量MainWindowController，然后立即销毁该变量，因为它超出了范围。

现在，接下来发生的事情的细节取决于这个类的析构函数的作用。我猜你正在对appWindow做一些让对象无效的事情（gtk_widget_destroy()可能吗？）。或者你可能在调用析构函数后尝试在信号中使用appWindow，这是未定义的行为。

GTK +：无法初始化GtkWidget *数据成员

1 个答案: