C++ Detect when user presses arrow key
Solution 1:
#include <conio.h>
#include <iostream>
using namespace std;
#define KEY_UP 72
#define KEY_DOWN 80
#define KEY_LEFT 75
#define KEY_RIGHT 77
int main()
{
int c = 0;
while(1)
{
c = 0;
switch((c=getch())) {
case KEY_UP:
cout << endl << "Up" << endl;//key up
break;
case KEY_DOWN:
cout << endl << "Down" << endl; // key down
break;
case KEY_LEFT:
cout << endl << "Left" << endl; // key left
break;
case KEY_RIGHT:
cout << endl << "Right" << endl; // key right
break;
default:
cout << endl << "null" << endl; // not arrow
break;
}
}
return 0;
}
output like this:
Up
Down
Right
Left
Up
Left
Right
Right
Up
detected arrow key press!
Solution 2:
The previous answer by arbboter is close but neglects the fact the arrow keys (and other special keys) return a scan code of two characters. The first is either (0) or (224) indicating the key is an extended one; the second contains the scan code value.
Without accounting for this, the ASCII values for "H", "K", "M", and "P" are misinterpreted as "Up", "Down", "Left", and "Right".
Here's a modified version of arbboter's code to demonstrate reading the extended value when one of the arrow keys is pressed:
#include <conio.h>
#include <iostream>
using namespace std;
#define KEY_UP 72
#define KEY_LEFT 75
#define KEY_RIGHT 77
#define KEY_DOWN 80
int main()
{
int c, ex;
while(1)
{
c = getch();
if (c && c != 224)
{
cout << endl << "Not arrow: " << (char) c << endl;
}
else
{
switch(ex = getch())
{
case KEY_UP /* H */:
cout << endl << "Up" << endl;//key up
break;
case KEY_DOWN /* K */:
cout << endl << "Down" << endl; // key down
break;
case KEY_LEFT /* M */:
cout << endl << "Left" << endl; // key left
break;
case KEY_RIGHT: /* P */
cout << endl << "Right" << endl; // key right
break;
default:
cout << endl << (char) ex << endl; // not arrow
break;
}
}
}
return 0;
}
Solution 3:
// Example for inputting a single keystroke in C++ on Linux
// by Adam Pierce <[email protected]> on http://www.doctort.org/adam/nerd-notes/reading-single-keystroke-on-linux.html
// This code is freeware. You are free to copy and modify it any way you like.
// Modify by me Putra Kusaeri
#include <iostream>
#include <termios.h>
#define STDIN_FILENO 0
using namespace std;
int main()
{
// Black magic to prevent Linux from buffering keystrokes.
struct termios t;
tcgetattr(STDIN_FILENO, &t);
t.c_lflag &= ~ICANON;
tcsetattr(STDIN_FILENO, TCSANOW, &t);
// Once the buffering is turned off, the rest is simple.
cout << "Enter a character: ";
char c,d,e;
cin >> c;
cin >> d;
cin >> e;
cout << "\nYour character was ";
// Using 3 char type, Cause up down right left consist with 3 character
if ((c==27)&&(d=91)) {
if (e==65) { cout << "UP";}
if (e==66) { cout << "DOWN";}
if (e==67) { cout << "RIGHT";}
if (e==68) { cout << "LEFT";}
}
return 0;
}
reference
Solution 4:
Here is an alternate way to do it without getch() using events (well commented and i tried to make it as simple as i could)
#include <iostream>
#include <Windows.h>
int main(int argc, char *argv[]){
HANDLE rhnd = GetStdHandle(STD_INPUT_HANDLE); // handle to read console
DWORD Events = 0; // Event count
DWORD EventsRead = 0; // Events read from console
bool Running = true;
//programs main loop
while(Running) {
// gets the systems current "event" count
GetNumberOfConsoleInputEvents(rhnd, &Events);
if(Events != 0){ // if something happened we will handle the events we want
// create event buffer the size of how many Events
INPUT_RECORD eventBuffer[Events];
// fills the event buffer with the events and saves count in EventsRead
ReadConsoleInput(rhnd, eventBuffer, Events, &EventsRead);
// loop through the event buffer using the saved count
for(DWORD i = 0; i < EventsRead; ++i){
// check if event[i] is a key event && if so is a press not a release
if(eventBuffer[i].EventType == KEY_EVENT && eventBuffer[i].Event.KeyEvent.bKeyDown){
// check if the key press was an arrow key
switch(eventBuffer[i].Event.KeyEvent.wVirtualKeyCode){
case VK_LEFT:
case VK_RIGHT:
case VK_UP:
case VK_DOWN: // if any arrow key was pressed break here
std::cout<< "arrow key pressed.\n";
break;
case VK_ESCAPE: // if escape key was pressed end program loop
std::cout<< "escape key pressed.\n";
Running = false;
break;
default: // no handled cases where pressed
std::cout<< "key not handled pressed.\n";
break;
}
}
} // end EventsRead loop
}
} // end program loop
return 0;
}
(Thanks to a commenter I now know this code is not standard, though it will work if you compile with g++
, more info in the comments)