无法在 gtk 中使用 c++ 创建 appindicator。 错误：g_dbus_proxy_new：断言“G_IS_DBUS_CONNECTION（连接）”失败

Question

I try to create indicator on Ubuntu. The following code works on Ubuntu 18, but not on Ubuntu 20.

void TestApplication(GtkApplication* app, gpointer user_data) {

    /* This function just keeps indicator exist. */
    gtk_application_window_new (app);

    GtkWidget* menu = gtk_menu_new();
    GtkWidget* menu_item = gtk_menu_item_new_with_label("menu_item");
    gtk_menu_shell_append(GTK_MENU_SHELL(menu), menu_item);

    AppIndicator *indicator = app_indicator_new("test_indicator", icon_path, APP_INDICATOR_CATEGORY_APPLICATION_STATUS);

    app_indicator_set_status(indicator, APP_INDICATOR_STATUS_ACTIVE);
    app_indicator_set_menu(indicator, GTK_MENU(menu));

    gtk_widget_show_all(menu);
}


int main(int argc, char *argv[]) {

    GtkApplication *app = gtk_application_new ("org.gtk.test", G_APPLICATION_FLAGS_NONE);
    g_signal_connect (app, "activate", G_CALLBACK (TestApplication), NULL);
    g_application_run (G_APPLICATION (app), argc, argv);
    g_object_unref (app);
    return 0;
}

Always showing error on Ubuntu 20:

GLib-GIO-CRITICAL **: 17:08:47.905: g_dbus_proxy_new: assertion 'G_IS_DBUS_CONNECTION (connection)' failed

Sometimes no errors are displayed and it runs successfully on Ubuntu 20.

If I modify the code to the following, still the same error message is displayed.

void TestApplication(GtkApplication* app, gpointer user_data) {

    /* This function just keeps indicator exist. */
    gtk_application_window_new (app);

    app_indicator_new("test_indicator", icon_path, APP_INDICATOR_CATEGORY_APPLICATION_STATUS);

}

If the program runs only "gtk_application_window_new" or "app_indicator_new" no error will be displayed.

My question is:

1.How can I solve this error?

2.How can I debug this?

Answer 1

I added this function "gtk_widget_show(window);" then it works fine.

void TestApplication(GtkApplication* app, gpointer user_data) {

    /* This function just keeps indicator exist. */
    GtkWidget* window = gtk_application_window_new (app);
    gtk_widget_show(window);

    GtkWidget* menu = gtk_menu_new();
    GtkWidget* menu_item = gtk_menu_item_new_with_label("menu_item");
    gtk_menu_shell_append(GTK_MENU_SHELL(menu), menu_item);

    AppIndicator *indicator = app_indicator_new("test_indicator", icon_path, APP_INDICATOR_CATEGORY_APPLICATION_STATUS);

    app_indicator_set_status(indicator, APP_INDICATOR_STATUS_ACTIVE);
    app_indicator_set_menu(indicator, GTK_MENU(menu));

    gtk_widget_show_all(menu);
}

Although the program doesn't show the error anymore, but I still don't know why it happened Hope someone can tell me why, thanks