从Fabric.js继承Fabric.Group的子类

从Fabric.js继承Fabric.Group的子类

出现错误“无法读取未定义的属性’async’”，因为找不到“ klass”-https:
//github.com/kangax/fabric.js/blob/master/src/util/misc.js#L214
-215
。

您必须将自定义对象分配给

fabric

对象-否则

canvas.loadFromJSON()

不起作用。

var fabric.CustomGroup = fabric.util.createClass(fabric.Group, {    type : 'customGroup',    initialize : function(objects, options) {        options || ( options = { });        this.callSuper('initialize', objects, options);        this.set('customAttribute', options.customAttribute || 'undefinedCustomAttribute');    },    toObject : function() {        return fabric.util.object.extend(this.callSuper('toObject'), { customAttribute : this.get('customAttribute')        });    },    _render : function(ctx) {        this.callSuper('_render', ctx);    }});

另外，您必须声明该

fromObject

方法-是必需的

loadFromJSON

。在这种情况下，您的对象是负载同步的。

fabric.CustomGroup.fromObject = function (object, callback) {    var _enlivenedObjects;    fabric.util.enlivenObjects(object.objects, function (enlivenedObjects) {        delete object.objects;        _enlivenedObjects = enlivenedObjects;    });    return new fabric.CustomGroup(_enlivenedObjects, object);};

如果您的自定义对象是异步加载的，则必须执行以下 *** 作：

fabric.CustomGroup.fromObject = function (object, callback) {    fabric.util.enlivenObjects(object.objects, function (enlivenedObjects) {        delete object.objects;        callback && callback(new fabric.CustomGroup(enlivenedObjects, object));    });};fabric.CustomGroup.async = true;

我做了一个小的jsfiddle测试用例：http :
//jsfiddle.net/Kienz/qPLY6/