想请问一下，在画布上画出了一个网络图由点和线构成，那么改如何拖动这个画布改变位置呢？能不能在canvas这个标签上绑定事件？
我写了个demo，你看看。
<body style="position: relative;">
<canvas id="myCanvas"
width="200"
height="100"
style="border:1px solid #c3c3c3;position:absolute;top:50px;left: 50px;">
Your browser does not support the canvas element.
</canvas>
<script>
var c = document.getElementById("myCanvas");
var cxt = c.getContext("2d");
cxt.moveTo(10,10);
cxt.lineTo(150,50);
cxt.lineTo(10,50);
cxt.stroke();
c.onmousedown = function(args){
var evt = args || event;
var StartX = evt.clientX;
var StartY = evt.clientY;
document.onmousemove = function(ev){
var iEvent = ev||event;
let left = iEvent.clientX - StartX;
let top = iEvent.clientY - StartY;
c.style.left = left + 50 + 'px';
c.style.top = top + 50 +'px';
}
document.onmouseup = function(){
document.onmousedown = null;
document.onmousemove = null;
};
return false;
}
</script>
</body>
<canvas id="myCanvas"
width="200"
height="100"
style="border:1px solid #c3c3c3;position:absolute;top:50px;left: 50px;">
Your browser does not support the canvas element.
</canvas>
<script>
var myCanvas = document.getElementById("myCanvas");
var cxt = myCanvas.getContext("2d");
cxt.moveTo(10,10);
cxt.lineTo(150,50);
cxt.lineTo(10,50);
cxt.stroke();
myCanvas.onmousedown = function(args){
var evt = args || event;
var offsetX = evt.clientX - myCanvas.offsetLeft;//鼠标按下的瞬间相对于myCanvas元素的位置（x）
var offsetY = evt.clientY - myCanvas.offsetTop;
document.onmousemove = function(ev){
var iEvent = ev ||event;
myCanvas.style.left = iEvent.clientX - offsetX + 'px';
myCanvas.style.top = iEvent.clientY - offsetY + 'px';
}
}
document.onmouseup = function(){
document.onmousedown = null;
document.onmousemove = null;
};
</script>
一楼这个是触边问题，触边后松开鼠标，还是能拖动；二楼这个是拖动整个画布，而不是画布中的某一个图形