Question

我正在寻找“如何将我的子弹移动到x，y coords”，但我找不到任何帮助或有用的话题..：|

嗯，有我的代码：

GoToMouse()
{
    this.goX = mouse.x;
    this.goY = mouse.y;

    this.dx = this.goX;
    this.dy = this.goY;


}

UpdatePosition()
{
    this.x += this.dx / 1000;
    this.y += this.dy / 1000;
}

当然，每60分钟，我画一个矩形！

所以，代码工作，当rect从0,0开始但是，当子弹开始时，例如10,10它不那么准确，而更大的起点更低的是子弹准确：|

谢谢！：）

Answer 1

这是animation tutorial。您可以通过示例查看如何在屏幕上为图形（例如项目符号）设置动画。

使用向量计算从[startX，startY]到[endX，endY]的增量[x，y]

// dx is the total distance to move in the X direction
var dx = endX - startX;

// dy is the total distance to move in the Y direction
var dy = endY - startY;

// use a pct (percentage) to travel the total distances
// start at 0% which == the starting point
// end at 100% which == then ending point
var pct=0;  

// use dx & dy to calculate where the current [x,y] is at a given pct
var x = startX + dx * pct/100;
var y = startY + dx * pct/100;

示例代码和演示，帮助您入门：

＆＃13;

// canvas vars
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
function reOffset(){
    var BB=canvas.getBoundingClientRect();
    offsetX=BB.left;
    offsetY=BB.top;        
}
var offsetX,offsetY;
reOffset();
window.onscroll=function(e){ reOffset(); }
window.onresize=function(e){ reOffset(); }

// animating vars
var pct=101;
var startX,startY,endX,endY,dx,dy;

// canvas styles
ctx.strokeStyle='skyblue';
ctx.fillStyle='blue';

// start animation loop running
requestAnimationFrame(animate);

// listen for mouse events
window.onmousedown=(function(e){handleMouseDown(e);});
window.onmouseup=(function(e){handleMouseUp(e);});

// constantly running loop
// will animate bullet 
function animate(time){
    // return if there's no bullet to animate
    if(++pct>100){requestAnimationFrame(animate);return;}
    // update
    x=startX+dx*pct/100;
    y=startY+dy*pct/100;
    // draw
    ctx.clearRect(0,0,cw,ch);
    ctx.beginPath();
    ctx.moveTo(startX,startY);
    ctx.lineTo(endX,endY);
    ctx.stroke();
    ctx.beginPath();
    ctx.arc(x,y,5,0,Math.PI*2);
    ctx.fill()
    // request another animation loop
    requestAnimationFrame(animate);
}

function handleMouseDown(e){
  // tell the browser we're handling this event
  e.preventDefault();
  e.stopPropagation();
  // save ending position
  startX=parseInt(e.clientX-offsetX);
  startY=parseInt(e.clientY-offsetY);
  // set flag
  pct=101;
}

function handleMouseUp(e){
  // tell the browser we're handling this event
  e.preventDefault();
  e.stopPropagation();
  // save ending position and vector
  endX=parseInt(e.clientX-offsetX);
  endY=parseInt(e.clientY-offsetY);
  dx=endX-startX;
  dy=endY-startY;
  // set pct=0 to start animating
  pct=0;
}

＆＃13;

body{ background-color: ivory; }
#canvas{border:1px solid red; }

＆＃13;

<h4>Drag the mouse<br>Mousedown sets starting position,<br>Mouseup sets ending position and animates.</h4>
<canvas id="canvas" width=512 height=512></canvas>

＆＃13;

如何将矩形移动到JS

1 个答案: