如何使此功能更新当前鼠标位置？

Question

我正在制作一个绘图板，我希望鼠标位置在拖动鼠标时在数组中更新。这是我的代码：

function penDown (x, y) {
  isPenDown = true;
  localPen.x = x;
  localPen.y = y;
}

var X = [],
Y = [],
i = -1;

function penMove (x, y) {
  if (isPenDown) {
     ++i; 
     X[i] = localPen.x;
     Y[i] = localPen.y;
     console.log("i is " + i + ", x is " + X[i] + ", y is " + Y[i]);
 }
};           

控制台日志显示，当您移动鼠标时，i 会不断更新，但鼠标的 X 和 Y 坐标不会改变 - 当您第一次按下鼠标时，它们只是停留在初始鼠标位置。

这就是我如何调用 penDown：

function pointerDownListener (e) {
  // Retrieve a reference to the Event object for this mousedown event.
  var event = e || window.event; 
  // Determine where the user clicked the mouse.
  var mouseX = event.clientX - canvas.offsetLeft;
  var mouseY = event.clientY - canvas.offsetTop;

  // Move the drawing pen to the position that was clicked
  penDown(mouseX, mouseY);
}

function pointerMoveListener (e) {

  var event = e || window.event; // IE uses window.event, not e
  var mouseX = event.clientX - canvas.offsetLeft;
  var mouseY = event.clientY - canvas.offsetTop;

  // Draw a line if the pen is down
  penMove(mouseX, mouseY);

}

Answer 1

可能是这样，因为你的函数 penDown 只被调用一次，所以分配给 localPen 的 x 和 y 的值不会改变。