官方的例子是基于原生的啊，如何在pixi引擎做离屏渲染呢。。。

主域代码：

        let openDataContext = wx.getOpenDataContext();

        let scanvas = openDataContext.canvas;

        scanvas.width = this.UI.bg.width;

        scanvas.height = this.UI.bg.height;

let btexture = new PIXI.BaseTexture(scanvas);

        let sprite = new PIXI.Sprite(new PIXI.Texture(btexture));

        sprite.anchor.set(0.5);

        this.UI.scene.addChild(sprite);

子域：

        let sharedCanvas = wx.getSharedCanvas()

     let context = sharedCanvas.getContext(‘2d’)

     context.fillStyle = ‘red’

        context.fillRect(0, 0, 100, 100)

无法实现渲染。。。