HTML Keydown even only once even when its being held it?
https://stackoverflow.com/questions/8736865
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14-04-2021 - |
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I have a Script in my HTML document that detects when one of the arrow keys is detected then it changes the URL of an iframe. When the key is released the iframe is changed again.
This works except during the time that the key is being held down it keeps repeating the action to set the iframe's url.
Is there a way so when its held down it only changes the iframe url once? Then when its released it changes the url back?
Extra: Iv created a page to control a remote control car over the web. It works great except for this problem. Basicly it changes the iframe url to a PHP page with a diffrent get variable for each arrow key. The PHP page then uses PHP Serial to send data to the serial port based on what ever variable was sent from the iframe (using GET).
Thanks for any help!!!
Edit: Here's a picture of the car. http://oi41.tinypic.com/21cimms.jpg
Edit 2
Heres the index.html
<!doctype html>
<html lang="en">
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script type="text/javascript">
function pause(ms) {
ms += new Date().getTime();
while (new Date() < ms){}
}
var keyBeingHeld = new Array();
keyBeingHeld[0] = false;//left
keyBeingHeld[1] = false;//right
keyBeingHeld[2] = false;//up
keyBeingHeld[3] = false;//down
function setControllerState(action){
leftPressState="up";
rightPressState="up";
upPressState="up";
downPressState="up";
if (keyBeingHeld[0]){
leftPressState="down";
}
if (keyBeingHeld[1]){
rightPressState="down";
}
if (keyBeingHeld[2]){
upPressState="down";
}
if (keyBeingHeld[3]){
downPressState="down";
}
var stateStr = "?upPressState="+upPressState+"&downPressState="+downPressState+"&leftPressState="+leftPressState+"&rightPressState="+rightPressState;
iframe = document.getElementById('stateFrame');
iframe.src = "BackEnd.php"+stateStr+"&action="+action;
}
$(document).keydown(function(event) {
if (!event) var event = window.event;
switch (event.keyCode) {
case 37:
if (!keyBeingHeld[0]){
keyBeingHeld[0] = true;
setControllerState ("leftArrowPress");
}
break;
case 38:
if (!keyBeingHeld[2]){
keyBeingHeld[2] = true;
setControllerState ("upArrowPress");
}
break;
case 39:
if (!keyBeingHeld[1]){
keyBeingHeld[1] = true;
setControllerState ("rightArrowPress");
}
break;
case 40:
if (!keyBeingHeld[3]){
keyBeingHeld[3] = true;
setControllerState ("downArrowPress");
}
break;
}
});
$(document).keyup(function(event) {
if (!event) var event = window.event;
switch (event.keyCode) {
case 37:
if (keyBeingHeld[0]){
keyBeingHeld[0] = false;
setControllerState ("leftArrowRelease");
}
break;
case 38:
if (keyBeingHeld[2]){
keyBeingHeld[2] = false;
setControllerState ("upArrowRelease");
}
break;
case 39:
if (keyBeingHeld[1]){
keyBeingHeld[1] = false;
setControllerState ("rightArrowRelease");
}
break;
case 40:
if (keyBeingHeld[3]){
keyBeingHeld[3] = false;
setControllerState ("downArrowRelease");
}
break;
}
});
</script>
</head>
<body>
<p>Press one of the arrow keys.</p>
<iframe id="stateFrame" name="stateFrame" style="width:160px;height:180px;" src="BackEnd.php?upPressState=up&downPressState=up&leftPressState=up&downPressState=up&action=none"></iframe>
<p>Thanks vdbuilder!</p>
</body>
</html>
Heres the backend.php
<?php
$opened = false;
$upPressState = cleanupSpecialChars($_GET['upPressState']) or $upPressState = 'up';
$downPressState = cleanupSpecialChars($_GET['downPressState']) or $downPressState = 'up';
$leftPressState = cleanupSpecialChars($_GET['leftPressState']) or $leftPressState = 'up';
$rightPressState = cleanupSpecialChars($_GET['rightPressState']) or $rightPressState = 'up';
$action = cleanupSpecialChars($_GET['action']) or $action = 'none';
// build your message from states and action, and send to serial port here
//the rest is to display the state
$pressedColor = "bbffbb";
$releasedColor = "bbbbbb";
$upArrowColor = $releasedColor;
$downArrowColor = $releasedColor;
$leftArrowColor = $releasedColor;
$rightArrowColor = $releasedColor;
if($upPressState == "down"){
sendCMD(25);
$upArrowColor = $pressedColor;
}
if($downPressState == "down"){
sendCMD(24);
$downArrowColor = $pressedColor;
}
if($leftPressState == "down"){
sendCMD(28);
$leftArrowColor = $pressedColor;
}
if($rightPressState == "down"){
sendCMD(29);
$rightArrowColor = $pressedColor;
}
//--- Up
if($upPressState == "up"){
sendCMD(15);
$upArrowColor = $releasedColor;
}
if($downPressState == "up"){
sendCMD(14);
$downArrowColor = $releasedColor;
}
if($leftPressState == "up"){
sendCMD(18);
$leftArrowColor = $releasedColor;
}
if($rightPressState == "up"){
sendCMD(19);
$rightArrowColor = $releasedColor;
}
echo("<html><head><style>");
echo("body{background-color:#000000;}
div#container{position:absolute;left:10px;top:10px;background-color:#eeeeee;
font-size:20px;padding:20px;width:100px;height:92px;text-align:center;}
div.arrow{position:absolute;width:30px;padding-top:2px;padding-bottom:2px;}
div#upArrow{left:55px;top:20px;background-color:#".$upArrowColor.";}
div#downArrow{left:55px;top:82px;background-color:#".$downArrowColor.";}
div#leftArrow{left:20px;top:50px;background-color:#".$leftArrowColor.";}
div#rightArrow{left:90px;top:50px;background-color:#".$rightArrowColor.";}
div#lastAction{position:absolute;left:0px;bottom:2px;font-size:14px;color:#ffffee;}");
echo("</style></head><body>");
echo("<div id='container'>
<div class='arrow' id='upArrow'>↑</div><div class='arrow' id='downArrow'>↓</div>
<div class='arrow' id='leftArrow'>←</div><div class='arrow' id='rightArrow'>→</div>
</div><div id='lastAction'>Last Action:<br />".$action."</div>");
echo("</body></html>");
//cleanup input
function cleanupSpecialChars($inStr){
$tempStr = htmlentities(stripslashes($inStr));
$retStr = str_replace(array('\\','/'), '', $tempStr);
return $retStr;
}
function sendCMD($cmd){
if($opened == false){
$fp =fopen("com4", "wb");
}
fwrite($fp,$cmd);
fclose($fp);
}
?>
Solution
Short answer:
Set a flag and test if it's set before you send the request.
Long answer:
Two files are required.
The two files below work as follows:
You navigate to FrontEnd.html. It maintains state and contains an iframe. The iframe is loaded with BackEnd.php (with its state variables set to default values and passed via the get method). When a key is pressed or released FrontEnd.html reloads the iframe with BackEnd.php (passing state via get method).
BackEnd.php sends the message to the serial port and displays the state of the arrow keys, based on the variables passed to it from FrontEnd.html.
<!doctype html>
<html lang="en">
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script type="text/javascript">
var controllerIsReady = false;
var keyEventBuffer = new Array();
var keyBeingHeld = new Array();
keyBeingHeld[0] = false;//left
keyBeingHeld[1] = false;//right
keyBeingHeld[2] = false;//up
keyBeingHeld[3] = false;//down
function controllerReady(){
controllerIsReady = false;
if(keyEventBuffer.length > 0){
bufferDiv = document.getElementById('eventBuffer');
buffHtmlStr = " ";
for (i=0;i<keyEventBuffer.length;i++){
tempStr = keyEventBuffer[i];
index = tempStr.indexOf("action", 0)+7;
keyEventStr = tempStr.substr(index,(tempStr.length-index));
buffHtmlStr = buffHtmlStr + "<br />" + keyEventStr;
}
bufferDiv.innerHTML = buffHtmlStr;
//shift event off and make request
stateStr = keyEventBuffer.shift();
iframe = document.getElementById('stateFrame');
iframe.src = "http://www.vdstudios.net/robotics/BackEnd.php"+stateStr;
}
else{
controllerIsReady = true;//alert("ready");
bufferDiv = document.getElementById('eventBuffer');
bufferDiv.innerHTML = "empty";
}
}
function setControllerState(action){
leftPressState="up";
rightPressState="up";
upPressState="up";
downPressState="up";
if (keyBeingHeld[0]){
leftPressState="down";
}
if (keyBeingHeld[1]){
rightPressState="down";
}
if (keyBeingHeld[2]){
upPressState="down";
}
if (keyBeingHeld[3]){
downPressState="down";
}
var stateStr = "?upPressState="+upPressState+"&downPressState="+downPressState+"&leftPressState="+leftPressState+"&rightPressState="+rightPressState+"&action="+action;
//add stateStr to fifo and if controllerIsReady call controllerReady
keyEventBuffer.push(stateStr);
if(controllerIsReady){
controllerReady();
}
}
$(document).keydown(function(event) {
if (!event) var event = window.event;
switch (event.keyCode) {
case 37:
if (!keyBeingHeld[0]){
keyBeingHeld[0] = true;
setControllerState ("leftArrowPress");
}
break;
case 38:
if (!keyBeingHeld[2]){
keyBeingHeld[2] = true;
setControllerState ("upArrowPress");
}
break;
case 39:
if (!keyBeingHeld[1]){
keyBeingHeld[1] = true;
setControllerState ("rightArrowPress");
}
break;
case 40:
if (!keyBeingHeld[3]){
keyBeingHeld[3] = true;
setControllerState ("downArrowPress");
}
break;
}
});
$(document).keyup(function(event) {
if (!event) var event = window.event;
switch (event.keyCode) {
case 37:
if (keyBeingHeld[0]){
keyBeingHeld[0] = false;
setControllerState ("leftArrowRelease");
}
break;
case 38:
if (keyBeingHeld[2]){
keyBeingHeld[2] = false;
setControllerState ("upArrowRelease");
}
break;
case 39:
if (keyBeingHeld[1]){
keyBeingHeld[1] = false;
setControllerState ("rightArrowRelease");
}
break;
case 40:
if (keyBeingHeld[3]){
keyBeingHeld[3] = false;
setControllerState ("downArrowRelease");
}
break;
}
});
</script>
</head>
<body>
<p>Press one of the arrow keys.</p>
<iframe id="stateFrame" name="stateFrame" style="width:160px;height:180px;" src="http://www.vdstudios.net/robotics/BackEnd.php?upPressState=up&downPressState=up&leftPressState=up&rightPressState=up&action=none"></iframe>
<div style="width:160px;padding:2px;padding-top:5px;background-color:#cccccc;text-align:center;">Event buffer<hr /><div id="eventBuffer" style="width:100%;">text</div></div>
</body>
</html>
BackEnd.php
<?php
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
// HTTP/1.0
header("Pragma: no-cache");
$upPressState = cleanupSpecialChars($_GET['upPressState']) or $upPressState = 'up';
$downPressState = cleanupSpecialChars($_GET['downPressState']) or $downPressState = 'up';
$leftPressState = cleanupSpecialChars($_GET['leftPressState']) or $leftPressState = 'up';
$rightPressState = cleanupSpecialChars($_GET['rightPressState']) or $rightPressState = 'up';
$action = cleanupSpecialChars($_GET['action']) or $action = 'none';
//send message to serial port
if($action == "upArrowPress"){
sendCMD(25);
}
else if($action == "downArrowPress"){
sendCMD(24);
}
else if($action == "leftArrowPress"){
sendCMD(28);
}
else if($action == "rightArrowPress"){
sendCMD(29);
}
else if($action == "upArrowRelease"){
sendCMD(15);
}
else if($action == "downArrowRelease"){
sendCMD(14);
}
else if($action == "leftArrowRelease"){
sendCMD(18);
}
else if($action == "rightArrowRelease"){
sendCMD(19);
}
//the rest is to display the state
$pressedColor = "bbffbb";
$releasedColor = "bbbbbb";
$upArrowColor = $releasedColor;
$downArrowColor = $releasedColor;
$leftArrowColor = $releasedColor;
$rightArrowColor = $releasedColor;
if($upPressState == "down"){
$upArrowColor = $pressedColor;
}
if($downPressState == "down"){
$downArrowColor = $pressedColor;
}
if($leftPressState == "down"){
$leftArrowColor = $pressedColor;
}
if($rightPressState == "down"){
$rightArrowColor = $pressedColor;
}
echo("<html><head><style>");
echo("body{background-color:#000000;}
div#container{position:absolute;left:10px;top:10px;background-color:#eeeeee;
font-size:20px;padding:20px;width:100px;height:92px;text-align:center;}
div.arrow{position:absolute;width:30px;padding-top:2px;padding-bottom:2px;}
div#upArrow{left:55px;top:20px;background-color:#".$upArrowColor.";}
div#downArrow{left:55px;top:82px;background-color:#".$downArrowColor.";}
div#leftArrow{left:20px;top:50px;background-color:#".$leftArrowColor.";}
div#rightArrow{left:90px;top:50px;background-color:#".$rightArrowColor.";}
div#lastAction{position:absolute;left:0px;bottom:2px;font-size:14px;color:#ffffee;}");
echo("</style></head><body onload='parent.controllerReady();'>");
echo("<div id='container'>
<div class='arrow' id='upArrow'>↑</div><div class='arrow' id='downArrow'>↓</div>
<div class='arrow' id='leftArrow'>←</div><div class='arrow' id='rightArrow'>→</div>
</div><div id='lastAction'>Last Action:<br />".$action."</div>");
echo("</body></html>");
//cleanup input
function cleanupSpecialChars($inStr){
$tempStr = htmlentities(stripslashes($inStr));
$retStr = str_replace(array('\\','/'), '', $tempStr);
return $retStr;
}
function sendCMD($cmd){
if($fp =fopen("com4", "wb")){//windows server
fwrite($fp,$cmd);
usleep(15000);
fclose($fp);
}
else if($fp =fopen("/dev/ttyS3", "wb")){//linux server
fwrite($fp,$cmd);
usleep(15000);
fclose($fp);
}
}
?>
You can see them running on my server here: http://www.vdstudios.net/robotics/FrontEnd.html
I can help you with building the message for the serial port if you give me details on what the device expects.
EDIT:
Added the code to build/send the message to the serial port. Also updated the running example with the same. You can see it at the link above.
Edit 2:
Added the code for buffering the keyEvents.
Added the code for sync'ing the backend and frontend states.
OTHER TIPS
Set a flag on keydown, clear it on keyup. Only fire the action if the flag isn't set.
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