GTK+: 无法初始化 GtkWidget * 数据成员

Question

我试图在构造函数中的 class 中分配一个 GtkWidget 指针，但是我遇到了运行时间错误。

#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);

但是这样可以吗？

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

您没有显示完整代码，但我认为问题出在这一行：

MainWindowController mainController(app);

这里你创建了一个类型为 MainWindowController 的局部变量 mainController，紧随其后，变量在超出范围时被销毁。

现在，接下来发生的细节取决于此 class 的析构函数的作用。我猜你正在对 appWindow 做一些事情，使对象无效（gtk_widget_destroy() 也许？）。或者您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

GTK+: Cannot initialize GtkWidget * data member

c++

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