NativeScript View _createUI 访问画布？

Question

我想通过 NativeScript 访问 Canvas，但我似乎找不到桥接入口点。因为 _CreateUI 不会在画布中传递，而 Java 中的 onDraw 会传递。

我想做以下 NativeScript Equiv：

@Override 
protected void onDraw(Canvas canvas) { 
    // floor the border width to avoid gaps between the border and the image 
    float roundedBorderWidth = (float) Math.floor(this.borderWidth); 
    float innerRadius = Math.max(0, this.cornerRadius - roundedBorderWidth); 

    // The border width is included in the padding so there is no need for 
    // clip if there is no inner border radius. 
    if (innerRadius != 0) { 
        this.rect.set( 
                roundedBorderWidth, 
                roundedBorderWidth,  
                this.getWidth() - roundedBorderWidth,  
                this.getHeight() - roundedBorderWidth); 

        this.path.reset(); 
        this.path.addRoundRect(rect, innerRadius, innerRadius, android.graphics.Path.Direction.CW); 

        canvas.clipPath(this.path); 
    } 

    super.onDraw(canvas); 
} 

谢谢 菲尔

Answer 1

这里是一个关于如何在 NativeScript Android 应用中构建 Canvas 的快速示例。使用带有 NativeScript 的 Placeholder component 来创建原生组件，除非您想编写插件/模块，否则您将完全采用不同的方法。

XML：

<Page> <Placeholder creatingView="createCanvas" height="200" /> </Page>

JavaScript 代码：

function createCanvas(args) {
     var canvas = new android.graphics.Canvas(); // construct an empty canvas
     args.view = canvas; // this puts the canvas on the interface where the placeholder is.
}
exports createCanvas = createCanvas;`