【发布时间】：2013-11-04 08:38:44
【问题描述】：
我有一个问题，希望有人能帮忙解决...
在我的应用程序中，我要求该工具能够在多个画布之间拖放图像。
在线提供了一些在多个画布之间拖放的预制示例，我找到了满足我需要的完美示例，由 RGraph 的 'Richard Heyes' 提供，您可以看到here（注意：您必须先单击图像才能开始拖动它）。
如您所见，在他的网站上，此拖放功能完美运行，但是当我将 javascript、html 和 css 传输到我的应用程序时 拖放图像的功能不起作用。
我在做什么：
<!DOCTYPE html>
<html>
<body>
<h1>My First Heading</h1>
<p>My first paragraph.</p>
<style type="text/css">
canvas {
border: 1px solid #808080;
}
</style>
<canvas style="float: left" height="125" width="400" id="cvs1">[No canvas support]</canvas>
<canvas style="float: left; margin-left: 100px" height="125" width="400" id="cvs2">[No canvas support]</canvas>
<script>
window.onload = function ()
{
var canvas1 = document.getElementById("cvs1");
var canvas2 = document.getElementById("cvs2");
var context1 = canvas1.getContext('2d');
var context2 = canvas2.getContext('2d');
var imageXY = {x: 5, y: 5};
/**
* This draws the image to the canvas
*/
function Draw ()
{
//Clear both canvas first
canvas1.width = canvas1.width
canvas2.width = canvas2.width
//Draw a red rectangle around the image
if (state && state.dragging) {
state.canvas.getContext('2d').strokeStyle = 'red';
state.canvas.getContext('2d').strokeRect(imageXY.x - 2.5,
imageXY.y - 2.5,
state.image.width + 5,
state.image.height + 5);
}
// Now draw the image
state.canvas.getContext('2d').drawImage(state.image, imageXY.x, imageXY.y);
}
canvas2.onclick =
canvas1.onclick = function (e)
{
if (state && state.dragging) {
state.dragging = false;
Draw();
return;
}
var mouseXY = RGraph.getMouseXY(e);
state.canvas = e.target;
if ( mouseXY[0] > imageXY.x
&& mouseXY[0] < (imageXY.x + state.image.width)
&& mouseXY[1] > imageXY.y
&& mouseXY[1] < (imageXY.y + state.image.height)) {
state.dragging = true;
state.originalMouseX = mouseXY[0];
state.originalMouseY = mouseXY[1];
state.offsetX = mouseXY[0] - imageXY.x;
state.offsetY = mouseXY[1] - imageXY.y;
}
}
canvas1.onmousemove =
canvas2.onmousemove = function (e)
{
if (state.dragging) {
state.canvas = e.target;
var mouseXY = RGraph.getMouseXY(e);
// Work how far the mouse has moved since the mousedon event was triggered
var diffX = mouseXY[0] - state.originalMouseX;
var diffY = mouseXY[1] - state.originalMouseY;
imageXY.x = state.originalMouseX + diffX - state.offsetX;
imageXY.y = state.originalMouseY + diffY - state.offsetY;
Draw();
e.stopPropagation();
}
}
/**
* Load the image on canvas1 initially and set the state up with some defaults
*/
state = {}
state.dragging = false;
state.canvas = document.getElementById("cvs1");
state.image = new Image();
state.image.src = 'http://www.rgraph.net/images/logo.png';
state.offsetX = 0;
state.offsetY = 0;
state.image.onload = function ()
{
Draw();
}
}
</script>
</body>
</html>
<!-- CODE COURTESY OF RICHARD HEYES OF RGRAPH
http://www.rgraph.net/blog/2013/january/an-example-of-html5-canvas-drag-n-drop.html -->
我在JSFiddle 上创建了相同的东西，但拖放仍然不起作用。
我是 html5 和 javascript 的新手，所以我确信它一定是我忽略的非常简单的东西，但我无法弄清楚它是什么。
非常感谢您的帮助，非常感谢。
【问题讨论】：
标签： javascript html drag-and-drop html5-canvas