问 使用fabric js连接两个对象

EN

您需要侦听 object:selected 事件以添加连接线，并侦听 object:moving 事件以更新线路坐标。

// function for drawing a line
function makeLine(coords) {
    return new fabric.Line(coords, {
        fill: 'red',
        stroke: 'red',
        strokeWidth: 5,
        selectable: false
var canvas; 
window.newAnimation = function(){
   canvas = new fabric.Canvas('canvas');
   var selectedElement = null;
   canvas.on('object:selected', function(options) {
       // we are doing t oadd a connection
       if (canvas.connect) {
           canvas.connect = false;
           var from = selectedElement.getCenterPoint();
           var to = options.target.getCenterPoint();
           var line = makeLine([from.x, from.y, to.x, to.y]);
           canvas.add(line);
           // these take care of moving the line ends when the object moves
           selectedElement.moveLine = function() {
               var from = selectedElement.getCenterPoint();
               line.set({ 'x1': from.x, 'y1': from.y });
           options.target.moveLine = function() {
               var to = options.target.getCenterPoint();
               line.set({ 'x2': to.x, 'y2': to.y });
       selectedElement = options.target;
   canvas.on('object:moving', function(e) {
        e.target.moveLine();
        canvas.renderAll();
window.addChild = function() {
   canvas.connect = true;
}

window.addChild跟踪是否单击Add子键(并应添加到按钮的onclick中)，以便下一个 object:selected 可以画线(否则它只会跟踪当前选定的元素)。

<button onClick="addChild()">Add Child</button>

请注意，对于完整的解决方案，您需要能够取消Add子方案，并且您可能希望处理对象大小调整(当前，当您移动对象时，行会更新，但是当您调整对象的大小时不会更新)。

小提琴- http://jsfiddle.net/ctcdaxop/

下面是您要寻找的新版本，包括对多个连接和删除的支持

添加子功能

function addChildLine(options) {
    canvas.off('object:selected', addChildLine);
    // add the line
    var fromObject = canvas.addChild.start;
    var toObject = options.target;
    var from = fromObject.getCenterPoint();
    var to = toObject.getCenterPoint();
    var line = new fabric.Line([from.x, from.y, to.x, to.y], {
        fill: 'red',
        stroke: 'red',
        strokeWidth: 5,
        selectable: false
    canvas.add(line);
    // so that the line is behind the connected shapes
    line.sendToBack();
    // add a reference to the line to each object
    fromObject.addChild = {
        // this retains the existing arrays (if there were any)
        from: (fromObject.addChild && fromObject.addChild.from) || [],
        to: (fromObject.addChild && fromObject.addChild.to)
    fromObject.addChild.from.push(line);
    toObject.addChild = {
        from: (toObject.addChild && toObject.addChild.from),
        to: (toObject.addChild && toObject.addChild.to) || []
    toObject.addChild.to.push(line);
    // to remove line references when the line gets removed
    line.addChildRemove = function () {
        fromObject.addChild.from.forEach(function(e, i, arr) {
            if (e === line)
                arr.splice(i, 1);
        toObject.addChild.to.forEach(function (e, i, arr) {
            if (e === line)
                arr.splice(i, 1);
    // undefined instead of delete since we are anyway going to do this many times
    canvas.addChild = undefined;
function addChildMoveLine(event) {
    canvas.on(event, function (options) {
        var object = options.target;
        var objectCenter = object.getCenterPoint();
        // udpate lines (if any)
        if (object.addChild) {
            if (object.addChild.from)
                object.addChild.from.forEach(function (line) {
                    line.set({ 'x1': objectCenter.x, 'y1': objectCenter.y });
            if (object.addChild.to)
                object.addChild.to.forEach(function (line) {
                    line.set({ 'x2': objectCenter.x, 'y2': objectCenter.y });
        canvas.renderAll();
window.addChild = function () {
    canvas.addChild = {
        start: canvas.getActiveObject()
    // for when addChild is clicked twice
    canvas.off('object:selected', addChildLine);
    canvas.on('object:selected', addChildLine);
}

因为我们没有画布引用，除非单击Add动画，所以处理程序必须附加在Add动画处理程序中

window.newAnimation = function () {
    canvas = new fabric.Canvas('canvas');
    // we need this here because this is when the canvas gets initialized
    ['object:moving', 'object:scaling'].forEach(addChildMoveLine)
}

删除对象时 删除行

window.deleteObject = function () {
    var object = canvas.getActiveObject();
    // remove lines (if any)
    if (object.addChild) {
        if (object.addChild.from)
            // step backwards since we are deleting
            for (var i = object.addChild.from.length - 1; i >= 0; i--) {
                var line = object.addChild.from[i];
                line.addChildRemove();
                line.remove();
        if (object.addChild.to)
            for (var i = object.addChild.to.length - 1; i >= 0; i--) {
                var line = object.addChild.to[i];
                line.addChildRemove();
                line.remove();