p5.js | keyPressed()函数
每当按下某个键时,都会调用keyPressed()函数。最近键入的 ASCII 密钥存储在 'key' 变量中,但它不区分大小写字符。可以在“keyCode”变量中使用它们各自的名称访问非 ASCII字符代码。
按住一个键可能会导致多次 keyPressed() 调用。这是由于操作系统如何处理按键并取决于计算机的配置方式。浏览器可能有自己的默认行为附加到各种键。这可以通过在方法末尾添加“return false”来防止。
句法:
keyPressed()
参数:此方法不接受任何参数。
以下示例说明了 p5.js 中的keyPressed()函数:
示例 1:
javascript
function setup() {
createCanvas(600, 200);
textSize(20);
text("Press any key to display it "
+ "on the screen", 10, 20);
}
function keyPressed() {
clear();
textSize(20);
text("Press any key to display it "
+ "on the screen", 10, 20);
textSize(100);
text(key, 100, 150);
}
javascript
let opac = 128;
function setup() {
createCanvas(700, 200);
background(0, 128, 0, opac);
textSize(22);
text("Press the left and right arrow"
+ " keys to change the opacity"
+ " of the color.", 10, 20);
}
function keyPressed() {
clear();
textSize(50);
text("Pressing: " + key, 100, 150);
// Reduce opacity if the left arrow is pressed
if (key == "ArrowLeft" && opac > 0)
opac -= 20;
// Increase opacity if the left arrow is pressed
else if (key == "ArrowRight" && opac < 255)
opac += 20;
// Set the new background color
background(0, 128, 0, opac);
textSize(22);
text("Press the left and right arrow"
+ " keys to change the opacity"
+ " of the color.", 10, 20);
}
输出:
示例 2:
javascript
let opac = 128;
function setup() {
createCanvas(700, 200);
background(0, 128, 0, opac);
textSize(22);
text("Press the left and right arrow"
+ " keys to change the opacity"
+ " of the color.", 10, 20);
}
function keyPressed() {
clear();
textSize(50);
text("Pressing: " + key, 100, 150);
// Reduce opacity if the left arrow is pressed
if (key == "ArrowLeft" && opac > 0)
opac -= 20;
// Increase opacity if the left arrow is pressed
else if (key == "ArrowRight" && opac < 255)
opac += 20;
// Set the new background color
background(0, 128, 0, opac);
textSize(22);
text("Press the left and right arrow"
+ " keys to change the opacity"
+ " of the color.", 10, 20);
}
输出:
在线编辑器: https://editor.p5js.org/
环境设置: https://www.geeksforgeeks.org/p5-js-soundfile-object-installation-and-methods/
参考: https://p5js.org/reference/#/p5/keyPressed