Question

我想在画布上使用真实物体图像（苹果）。我应该能够用鼠标拖动它到所需的位置。在任何击键或特定键（比如空格键）上，我应该能够将对象移动到画布上的随机位置。

Answer 1

<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css"/> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>

<style>
body{ background-color: ivory; }
canvas{border:1px solid red;}
</style>

<script>
$(function(){


var img = new Image();
img.onload = function(){
    ctx.drawImage(img, 0,0);
};
img.src = "http://images.christmastimeclipart.com/images/2/1271716593176_1788/img_1271716593176_17881.jpg";

var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var canvasWidth=canvas.width;
var canvasHeight=canvas.height;
var isDragging=false;

function handleMouseDown(e){
  canMouseX=parseInt(e.clientX-offsetX);
  canMouseY=parseInt(e.clientY-offsetY);
  // set the drag flag
  isDragging=true;
}

function handleMouseUp(e){
  canMouseX=parseInt(e.clientX-offsetX);
  canMouseY=parseInt(e.clientY-offsetY);
  // clear the drag flag
  isDragging=false;
}

function handleMouseOut(e){
  canMouseX=parseInt(e.clientX-offsetX);
  canMouseY=parseInt(e.clientY-offsetY);
  // user has left the canvas, so clear the drag flag
  //isDragging=false;
}

function handleMouseMove(e){
  canMouseX=parseInt(e.clientX-offsetX);
  canMouseY=parseInt(e.clientY-offsetY);
  // if the drag flag is set, clear the canvas and draw the image
  if(isDragging){
      ctx.clearRect(0,0,canvasWidth,canvasHeight);
      ctx.drawImage(img,canMouseX-128/2,canMouseY-120/2,128,120);
  }
}

$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUp(e);});
$("#canvas").mouseout(function(e){handleMouseOut(e);});

}); // end $(function(){});
</script>

</head>

<body>
<canvas id="canvas" width=400 height=300></canvas>
</body>
</html>

在HTML5中拖动画布上的对象

1 个答案: