在C中使用箭头键

Question

I've finally got a hold of the Arrow Keys in C. I've found out how to have C detect them and have actually made a program of it.

The problem is... The program is bugged. I don't know what I've done wrong.

CODE:

#include <stdio.h>
main()
{
    char menitem[3][32], key, key2;
    int i = 0;
    strcpy(menitem[0], "Option 1 [X]");
    strcpy(menitem[1], "Option 2 [ ]");
    strcpy(menitem[2], "Option 3 [ ]");
    start:
    system("cls");
    printf("%s\n%s\n%s", menitem[0], menitem[1], menitem[2]);
    key = getch();
    key2 = 0;
    if(key = 0xE0)
    key2 = getch();
    ret:
    if(i == 0)
    {
         switch(key2)
         {
        case 80:
            strcat(menitem[0], "\b\b ]");
            i++;
            strcat(menitem[i], "\b\bX]");
            goto start;
        default: goto ret;
     }
}
else if(i == 2)
{
     switch(key2)
    {
    case 72:
        strcat(menitem[2], "\b\b ]");
        i--;
        strcat(menitem[i], "\b\bX]");
        goto start;
        default: goto ret;
    }
}
else
{
    switch(key2)
    {
        case 80:
        strcat(menitem[i], "\b\b ]");
        i++;
        strcat(menitem[i], "\b\bX]");
        goto start;
        case 72:
        strcat(menitem[i], "\b\b ]");
        i--;
        strcat(menitem[i], "\b\bX]");
        goto start;
        default: goto ret;
    }
}
}

Here's the problem:

When I go up from Option 2, Option 3 turns into "X]". Any idea why?

Try compiling it and keep on using the arrow keys. See what happens. Will appreciate any help given!

Answer 1

Doing /b and erasing input, then adding input back, over and over, is not a good idea. For one, if the user presses lots of arrow keys, you'll get tons of backspaces/erased characters and your strings will grow very large. You are having problems because you are deleting too many characters in certain situations. Instead, just do a memory modification of the character inside the []. I will edit this post with a working solution.

Edit Here is a working solution:

#include <stdio.h>
int main()
{
    char menitem[3][32], key, key2;
    int i = 0;
    int currentlySelectedItem = 1;
    strcpy(menitem[0], "Option 1 [X]");
    strcpy(menitem[1], "Option 2 [ ]");
    strcpy(menitem[2], "Option 3 [ ]");
    while(1)
    {
        system("cls");
        printf("%s\n%s\n%s", menitem[0], menitem[1], menitem[2]);
        key = getch();
        key2 = 0;
        if(key == -32)
        {
            key2 = getch();
        }
        else
        {
            continue;
        }
        if(key2 == 80)
        {
            currentlySelectedItem++;
        }
        else if(key2 == 72)
        {
            currentlySelectedItem--;
        }

        //make sure the selected item stays in range
        if(currentlySelectedItem < 1)
            currentlySelectedItem = 1;
        if(currentlySelectedItem > 3)
            currentlySelectedItem = 3;

        menitem[0][10] = ' ';
        menitem[1][10] = ' ';
        menitem[2][10] = ' ';
        menitem[currentlySelectedItem-1][10] = 'X';

    }

}