how to make my player move in diagonal lines and horizontal lines

问题

i have the following code to make an ellipse move to the left right top and bottom. but now the player can only move in one direction at the time. so if the player moves to the left he cant move to the to the top or bottom. how do i make my code so the player can move both left and right and to the top and the bottom at the same time? any suggestions are appreciated. :)

see the code that i have so far:

void userInput() {
    if (keyPressed && (key == 's')) {
      speedY = 1;
      println("yes");
    }
    if (keyPressed && (key == 'w')) {
      speedY = -1;
      println("yes");
    }
    if (keyPressed && (key == 'd')) {
      println("yes");
      speedX = 1;
    }
    if (keyPressed && (key == 'a')) {
      println("yes");
      speedX = -1;
    }  
    if (keyPressed &&(key != 'a' && key != 'd')) {
      println("no");
      speedX = 0;
    }

    if (keyPressed &&(key != 'w' && key != 's')) {
      println("no");
      speedY =0;
    }
  }

void movement() {
    x = x + speedX;
    y = y + speedY;

}

回答1:

One way to do this is to use boolean values to keep track of which keys are pressed. Set them to true in keyPressed(), set them to false in keyReleased(), and use them to move your actor in the draw() function.

boolean upPressed = false;
boolean downPressed = false;
boolean leftPressed = false;
boolean rightPressed = false;

float circleX = 50;
float circleY = 50;

void draw() {
  background(200);  

  if (upPressed) {
    circleY--;
  }

  if (downPressed) {
    circleY++;
  }

  if (leftPressed) {
    circleX--;
  }

  if (rightPressed) {
    circleX++;
  }

  ellipse(circleX, circleY, 20, 20);
}

void keyPressed() {
  if (keyCode == UP) {
    upPressed = true;
  }
  else if (keyCode == DOWN) {
    downPressed = true;
  }
  else if (keyCode == LEFT) {
    leftPressed = true;
  }
  else if (keyCode == RIGHT) {
    rightPressed = true;
  }
}

void keyReleased() {
  if (keyCode == UP) {
    upPressed = false;
  }
  else if (keyCode == DOWN) {
    downPressed = false;
  }
  else if (keyCode == LEFT) {
    leftPressed = false;
  }
  else if (keyCode == RIGHT) {
    rightPressed = false;
  }
}

_{(source: happycoding.io)}

More info can be found in this tutorial on user input in Processing.

来源：https://stackoverflow.com/questions/38804901/how-to-make-my-player-move-in-diagonal-lines-and-horizontal-lines

标签

java

processing

game-physics