模拟C中的退格按钮按下gtk [英] Simulate backspace button press gtk in C

问题描述

我正在gtk + 3/C中的树莓派上编写一个需要虚拟小键盘(例如0-9，退格并输入)的应用.我将它与触摸屏一起使用，因此没有可用的键盘或鼠标(就像售货亭一样).

I am writing an app on raspberry in gtk+3/C which requires a virtual numpad (e.g 0-9, backspace and enter). I will use it with a touch screen, so no keyboard or mouse available (just like a kiosk).

我正在采用此代码，该代码允许我使用按钮按下来模拟数字并显示到条目，但是我一直坚持给它使用退格功能(返回并删除一个先前的字符)并输入功能(例如，当输入完毕，按一下该按钮将帮助我返回主屏幕.

I am adopting this code which allows me to use button press to emulate the number and display to an entry, however I am stuck at giving it the backspace function (go back and delete one previous char) and enter function (e.g when I'm done with input, press that button will help me to get back to the main screen).

/*
   gcc -Wall keyboard1.c -o keyboard1 `pkg-config --cflags --libs gtk+-3.0`
   Tested with GTK3.22 and GTK3.22 on Ubuntu18.04   
*/
#include<gtk/gtk.h>

struct key{
    gint id;
    GtkWidget *button;
  };

static const gchar letters[18]="QWERTYASDFGHZXCVBN";
//Need single chars as strings.
static gchar single_char[2]={'A', '\0'};

static void button_clicked(GtkWidget *button, gpointer *user_data)
  {
    gpointer *button_index=g_hash_table_lookup((GHashTable*)user_data[0], button);
    g_print("Button index %i\n", (gint)(*button_index));
    gint index=(gint)(*button_index);
    single_char[0]=letters[index];
    gchar *string=g_strdup_printf("%s%s", gtk_entry_get_text(GTK_ENTRY(user_data[1])), single_char);
    gtk_entry_set_text(GTK_ENTRY(user_data[1]), string);
    g_free(string);
  }
int main(int argc, char *argv[])
  {
    gtk_init (&argc, &argv);
    gint i=0;
    gint j=0;
    
    GtkWidget *window=gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title(GTK_WINDOW(window), "Keyboard");
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 200);
    gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    GtkWidget *entry=gtk_entry_new();
    gtk_widget_set_hexpand(entry, TRUE);

    //Save buttons in an array.
    struct key k1;
    GArray *keyboard=g_array_new(FALSE, FALSE, sizeof(struct key));    
    for(i=0;i<18;i++)
      {
        single_char[0]=letters[i];
        k1.id=i;
        k1.button=gtk_button_new_with_label(single_char);
        g_array_append_val(keyboard, k1);
      }   
 
    //A hash table to look up array index values.
    struct key *p1=NULL;
    GHashTable *hash_table=g_hash_table_new(NULL, NULL);
    for(i=0;i<18;i++)
      {
        p1=&g_array_index(keyboard, struct key, i);
        g_hash_table_insert(hash_table, p1->button, &(p1->id));
      }

    gpointer user_data[2]={hash_table, entry};
    GtkWidget *grid1=gtk_grid_new();
    for(i=0;i<3;i++)
      {
        for(j=0;j<6;j++)
          {
            p1=&g_array_index(keyboard, struct key, i*6+j);
            gtk_grid_attach(GTK_GRID(grid1), p1->button, j, i, 1, 1);
            g_signal_connect(p1->button, "clicked", G_CALLBACK(button_clicked), user_data);
          }
      } 

    GtkWidget *scroll=gtk_scrolled_window_new(NULL, NULL);
    gtk_widget_set_vexpand(scroll, TRUE);
    gtk_widget_set_hexpand(scroll, TRUE);
    gtk_container_add(GTK_CONTAINER(scroll), grid1);

    GtkWidget *expander=gtk_expander_new("Keyboard");
    gtk_widget_set_vexpand(expander, TRUE);
    gtk_widget_set_hexpand(expander, TRUE);
    gtk_container_add(GTK_CONTAINER(expander), scroll);

    GtkWidget *grid2=gtk_grid_new();
    gtk_grid_attach(GTK_GRID(grid2), expander, 0, 0, 1, 1);
    gtk_grid_attach(GTK_GRID(grid2), entry, 0, 1, 1, 1);

    gtk_container_add(GTK_CONTAINER(window), grid2);

    gtk_widget_show_all(window);

    gtk_main();

    g_hash_table_destroy(hash_table);
    g_array_free(keyboard, TRUE);

    return 0;
  }  

这是链接张贴.

我尝试用\b，\n和\t替换gchar letters[18]="QWERTYASDFGHZXCVBN";中的char，以替换退格键，换行符和制表符，但是只有\t可以. \b给了我一个奇怪的符号:

I have tried to replace a char in the gchar letters[18]="QWERTYASDFGHZXCVBN"; with \b, \n and \t as to replace backspace, newline and tab, but only \t works. \b gave me a strange symbol:

您能给我一些建议吗.非常感谢你！

Could you give me suggestions on how to do it. Thank you very much!

推荐答案

您似乎混淆了两件事:gtk_entry_set_text将GTK元素的标题设置为字符串.它不解释它的字符.

You seem to confuse two things: gtk_entry_set_text sets the caption of a GTK element to a string of characters. It does not interpret it's characters.

这就是为什么gtk_entry_set_text可以很好地与非控制字符配合使用，但会卡在\b上的原因.您必须使用gtk_propagate_event发送一个GtkEvent才能正确处理此问题(请参见 和此处). \n不是控制字符是这样的:您撰写的GTK元素可能不支持换行符，并且 Return 会被解释为确认.

That's why gtk_entry_set_text works well with non-control characters but stuck at \b. You had to send a GtkEvent using gtk_propagate_event to handle this properly (see here and here). \n is not a control character is this manner: It's possible that the GTK element your writing to just doesn't support newlines and Return would be interpreted as confirmation.

这篇关于模拟C中的退格按钮按下gtk的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！