处理时移动矩形？

Question

I have the following code (I didn't write the setup and the draw here) and I want to move a rectangle on Processing. Left if I press 'a' and right if I press 'd'. With this code I do it but if moveTo is a low number, the rectangle moves too slowly and if moveTo is a high number, the rectangle moves jerkily. It's not fluid... How can I do this animation?

int moveTo = 5;
void keyPressed()
{
  if (key == 'a')
  {
       xTopRect = xTopRect - moveTo;
       xBottomRect = xBottomRect - moveTo;
       xFstPointTriangle = xFstPointTriangle - moveTo;
       xSndPointTriangle = xSndPointTriangle - moveTo;
       xTrdPointTriangle = xTrdPointTriangle - moveTo;
  }
  else if (key == 'd')
  {
       xTopRect = xTopRect + moveTo;
       xBottomRect = xBottomRect + moveTo;
       xFstPointTriangle = xFstPointTriangle + moveTo;
       xSndPointTriangle = xSndPointTriangle + moveTo;
       xTrdPointTriangle = xTrdPointTriangle + moveTo;
   }  
}

I've found this solution and it works (don't look at the variables) I call move() in draw()

void move()
{
  if (keyPressed) {
    if (key == 'a') {
      x = x - speed;
    } else if (key == 'd') {
      x = x + speed;
    }
  }
}

Answer 1

int moveTo = 5;
int MAX_MOVE_TO=100;
int counter=0;
void keyPressed()
{

  counter++;
  if(counter==(MAX_MOVE_TO-moveTo))
  {
     if (key == 'a')
     {
           xTopRect = xTopRect - 1;
           xBottomRect = xBottomRect - 1;
           xFstPointTriangle = xFstPointTriangle - 1;
           xSndPointTriangle = xSndPointTriangle - 1;
           xTrdPointTriangle = xTrdPointTriangle - 1;
     }
     else if (key == 'd')
     {
           xTopRect = xTopRect + 1;
           xBottomRect = xBottomRect + 1;
           xFstPointTriangle = xFstPointTriangle + 1;
           xSndPointTriangle = xSndPointTriangle + 1;
           xTrdPointTriangle = xTrdPointTriangle + 1;
     }  
     counter=0;
  }
}

just try different values of moveTo between 0 and 99 please. It should move smoothly at all speeds.

You are moving objects with a keypress but you can do it in a different thread so it can move when you are not pressing a key too.

Answer 2

Currently, your code is using a KeyListener , I assume, to trigger the movement. One thing you could do is to create and ArrayList<Integer> to hold the values of the keys that are down. Then, in a loop, check the ArrayList for the A and D key values, and move if they are in it.

The problem right now is that the KeyListener only registers a KeyEvent every do often. With this solution, you will be able to control how often the rectangle's location updates.

ArrayList<Integer> keysDown = new ArrayList<Integer>();
void keyPressed(KeyEvent e) {
    if (!keysDown.contains(e.getKeyCode()) {
        keysDown.add(e.getKeyCode());
    }
}
void keyReleased(KeyEvent e) {
if (keysDown.contains(e.getKeyCode()) {
        keysDown.remove(e.getKeyCode());
    }
}

Then in your update or draw loop,

if (keysDown.contains(KeyEvent.VK_A)) {
    xTopRect = xTopRect - moveTo;
    xBottomRect = xBottomRect - moveTo;
    xFstPointTriangle = xFstPointTriangle - moveTo;
    xSndPointTriangle = xSndPointTriangle - moveTo;
    xTrdPointTriangle = xTrdPointTriangle - moveTo;
} else if (keysDown.contains(KeyEvent.VK_D)) {
   xTopRect = xTopRect + moveTo;
   xBottomRect = xBottomRect + moveTo;
   xFstPointTriangle = xFstPointTriangle + moveTo;
   xSndPointTriangle = xSndPointTriangle + moveTo;
   xTrdPointTriangle = xTrdPointTriangle + moveTo;
}