Question

当程序最初运行时，打印语句，打印对应于指针的有效十六进制代码。但是，当我单击屏幕，并通过“clicked”回调调用handleClick方法时，会在屏幕上显示0x0。发生了什么？为什么我的电路板对象突然变为空？

#include <stdio.h>
#include <stdlib.h>
#include <gtk/gtk.h>
#include "board.h"

void printBoard(Board *board);
void handleClick(GtkWidget *widget, GdkEventButton *event, cairo_t *cr, gpointer data);

  gboolean draw_cb(GtkWidget *widget, cairo_t *cr, gpointer data)
  {
    Board *temp = (Board *)data;
    printf("%p\n",temp);
    return TRUE;
  }

  void handleClick (GtkWidget *widget, GdkEventButton *event, cairo_t *cr, gpointer data)
  {
    Board *temp = (Board *)data;
    printf("%p\n",temp);
  }

  void start(Board *newBoard)
  {
      GtkWidget *window;
      GtkWidget *da;
      GtkWidget *frame;

      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
      char string[40];
      snprintf(string, sizeof(string), "Connect %d-%d",newBoard->k,newBoard->n);

      gtk_window_set_default_size (GTK_WINDOW(window), 400, 400);
      gtk_window_move(GTK_WINDOW(window), 100, 100);     
      g_signal_connect (GTK_WINDOW(window), "destroy", G_CALLBACK (gtk_main_quit), NULL);

      da = gtk_drawing_area_new ();
      gtk_widget_set_size_request (da, 500, 500);

      frame = gtk_frame_new (NULL);
      gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
      gtk_container_add (GTK_CONTAINER (window), frame);

      gtk_container_add (GTK_CONTAINER (frame), da);

      gtk_widget_set_events (da, gtk_widget_get_events (da)
                     | GDK_BUTTON_PRESS_MASK);

      g_signal_connect (da, "draw",
              G_CALLBACK (draw_cb), newBoard);

       g_signal_connect (da, "button-press-event",
              G_CALLBACK (handleClick), newBoard);

      gtk_widget_show_all (window);
  }

Answer 1

根据reference manual，button-press-event信号处理程序的原型如下。

gboolean user_function (GtkWidget *widget,
                        GdkEvent  *event,
                        gpointer   user_data)

如果您从cairo_t *cr功能handleClick删除data参数即可。

Answer 2

正如Szilard所说，你正在使用handleClick函数的错误原型。

button-press-event信号处理程序具有以下原型：

gboolean user_function (GtkWidget *widget,
                        GdkEvent  *event,
                        gpointer   user_data)

要解决您的错误，您需要：

删除cairo_t *cr参数。它收到data的值。
修复event类型GdkEvent *，而不是GdkEventButton *
修复返回值，这是一个布尔值，而不是无效，这对于确定事件是否传播很重要。

无法将参数传递给GTK回调

2 个答案: