线条流动效果

图论中边是重要元素，它连接各个顶点构成拓扑图，有向图中，边具有方向性，在画布中表现为箭头，在实际应用中，边可以代表链路，链路上不只是有方向，还有流量，信号种类等信息，光用箭头表现力就不够了，可增加线条线型，以及流动效果来体现，这里介绍 Qunee 1.6 中线条流动效果的实现

虚线流动效果

虚线流动效果在[连线示例](http://demo.qunee.com/#Edge Demo)中有演示，使用虚线偏移量样式，不断增大，实现线条的流动

虚线流动代码

var offset = 0;
var index = 0;
var timer = setInterval(function(){
    offset += -1;
//    edge2.setStyle(Q.Styles.EDGE_LINE_DASH_OFFSET, offset);
    edge1.setStyle(Q.Styles.EDGE_LINE_DASH_OFFSET, offset);
    index++;
    index = index%20;
    edge2.setStyle(Q.Styles.ARROW_TO_OFFSET, -0.3 -0.02 \* (20 - index));
    edge1.setStyle(Q.Styles.ARROW_FROM_OFFSET, {x: 0.3 + 0.02 \* (20 - index), y: -10});
}, 150);

运行效果

定制流动效果

对于更高级的流动需求，需要定制来实现，原理是在线条上挂载一个小图标，让这个图标沿线移动，从而形成动画效果

实现代码

下面的代码实现在线条上移动小图标

var line = graph.createShapeNode("Line");
line.moveTo(-100, 0);
line.lineTo(200, 0);
line.curveTo(300, 0, 300, 100, 200, 100);
line.lineTo(0, 100);
line.closePath();
line.setStyle(Q.Styles.SHAPE_STROKE_STYLE, "#2898E0");
line.setStyle(Q.Styles.SHAPE_LINE_DASH, [8, 5, 0.1, 6]);
line.setStyle(Q.Styles.SHAPE_STROKE, 3);
line.setStyle(Q.Styles.LINE_CAP, "round");
line.setStyle(Q.Styles.SHAPE_OUTLINE_STYLE, "#fcfb9b");
var ui = new Q.ImageUI("images/flow.png");
ui.position = {x: 0, y: 0};
ui.size = {width: 20};
ui.renderColor = "#F00";
line.addUI(ui);
setTimeout(function A(){
    var x = ui.position.x + 20;
    ui.position = {x: x % (ui.parent.length || 1), y: 0};
    line.invalidate();
    setTimeout(A, 300);
}, 100)

运行效果

进一步封装

上面的实现太随意，实际使用不太方便，可以进一步封装成专门用于流动支持的类，这样可以通过一个定时器实现所有的流动支持，我们创建一个FlowingSupport的类，详细代码如下

FlowingSupport类代码

function FlowingSupport(graph) {
    this.flowMap = {};
    this.graph = graph;
}
FlowingSupport.prototype = {
    flowMap: null,
    length: 0,
    gap: 40,
    graph: null,
    addFlowing: function (edgeOrLine, count, byPercent) {
        var flowList = this.flowMap[edgeOrLine.id];
        if(!flowList){
            flowList = this.flowMap[edgeOrLine.id] = [];
            this.length++;
        }
        count = count || 1;
        while(--count >= 0){
            var ui = new Q.ImageUI("network/images/flow.png");
            ui.position = {x: 0, y: 0};
            ui.size = {width: 20};
            ui.renderColor = "#F00";
            flowList.push(ui);
            flowList.byPercent = byPercent;
            edgeOrLine.addUI(ui);
        }
    },
    removeFlowing: function(id){
        var flowList = this.flowMap[id];
        if(!flowList){
            return;
        }
        var edgeOrLine = this.graph.getElement(id);
        if(edgeOrLine){
            flowList.forEach(function(ui){
                edgeOrLine.removeUI(ui);
            })
        }
        this._doRemove(id);
    },
    _doRemove: function(id){
        delete this.flowMap[id];
        this.length--;
    },
    timer: null,
    perStep: 10,
    stop: function(){
        clearTimeout(this.timer);
    },
    start: function(){
        if(this.timer){
            clearTimeout(this.timer);
        }
        var offset = 0;
        var scope = this;
        scope.timer = setTimeout(function A() {
            if (!scope.length) {
                scope.timer = setTimeout(A, 2000);
                offset = 0;
                return;
            }
            offset += 1;
            for(var id in scope.flowMap){
                var ui = scope.graph.getUI(id);
                if(!ui){
                    scope._doRemove(id);
                    continue;
                }
                var lineLength = ui.length;
                if(!lineLength){
                    continue;
                }
                var flowList = scope.flowMap[id];
                if(flowList.byPercent){
                    //按百分比，0 - 1跑完整条线，线长度不同，速度也不同，跑完一圈的时间相同
                    var x = offset \* 2;
                    var gap = 15;
                    scope.flowMap[id].forEach(function(ui){
                        ui.position = {x: (x % 100) / 100, y: 0};
                        x += gap;
                    });
                }else{
                    //按固定距离移动，速度相同，线条越长跑完一圈的时间越长
                    var x = offset \* scope.perStep;
                    scope.flowMap[id].forEach(function(ui){
                        ui.position = {x: x % lineLength, y: 0};
                        x += scope.gap;
                    });
                }
                scope.graph.invalidateUI(ui);
                //dashed line
                var data = ui.data;
                if(data instanceof Q.Edge){
                    if(data.getStyle(Q.Styles.EDGE_LINE_DASH)){
                        data.setStyle(Q.Styles.EDGE_LINE_DASH_OFFSET, -offset);
                    }
                }else if(data instanceof Q.ShapeNode){
                    if(data.getStyle(Q.Styles.SHAPE_LINE_DASH)) {
                        data.setStyle(Q.Styles.SHAPE_LINE_DASH_OFFSET, -offset);
                    }
                }
            }
            scope.timer = setTimeout(A, 200);
        }, 200);
    }
}

使用如下

这里的第二个参数为图标数量，第三个参数为是否按百分比流动，如果按百分比流动，每次移动的距离为线条长度的百分之二，这意味着不同长度的线条流动一圈，花费的时间相同

var flowingSupport = new FlowingSupport(graph);
flowingSupport.addFlowing(edge, 3);
flowingSupport.addFlowing(edge2, 1);
flowingSupport.addFlowing(line, 1, true);
flowingSupport.addFlowing(line2, 2, true);
graph.callLater(function(){
    flowingSupport.start();
})

运行效果

在线演示

[http://demo.qunee.com/#Flowing Demo](http://demo.qunee.com/#Flowing Demo)