.....
        this.totalSharedTexture = new cc.RenderTexture();
        this.totalSharedTexture.initWithSize(550, 4000);//必须操作，否则readPixels返回null,且高度超过4096 ios崩溃
        var openDataContext = wx.getOpenDataContext();
        openDataContext.canvas.width = 550;
        openDataContext.canvas.height = 4000;
        //发送开放域消息
        Platform.postMessage({
            action: "Total"
        });
        this.totalRenderSchedule = () => {
        	//复制Canvas到纹理
        	var openDataContext = wx.getOpenDataContext();
        	var sharedCanvas = openDataContext.canvas;
        	this.totalSharedTexture.initWithElement(sharedCanvas);
        	this.spriteTotal.spriteFrame = new cc.SpriteFrame(this.totalSharedTexture);
            //计算高度
            let rowNum = 0;
            let data = this.totalSharedTexture.readPixels();//像素点数据
            //每个像素点32位，即4个byte，依次为为RGBA值
            //我的排行榜数据宽550高100为一条数据，所以一条数据所用的字节量为
            let rowDataBytes = 4 * 550 * 100;
            //大体估计下头像的坐标，找一个点，这个点刚好位于头像上，Alpha值必定不为0的
            let firstPixelIndex = 4 * 550 * 70 + 150 * 4;
            for (var i = 0; i <= parseInt(data.length / rowDataBytes); i++) {
                rowNum = i;
                //读取RGBA的Alpha值
                let a = data[firstPixelIndex + i * rowDataBytes + 3];
                if (a == 0) {
                   break;
                }
            }
            //重置高度this.content是scrollView中的Content节点
            this.content.setContentSize(cc.size(550, 100 * rowNum));
        };
        //为防止接口调用慢,1秒后读取开放域,执行三次。
        this.schedule(this.totalRenderSchedule, 1, 3);
.....