How to draw filled triangle on android Canvas

Question

I have class MyView that extends View class. MyView should draw filled triangle. I drew a triangle but I cannot get it filled. This is my onDraw() method:

@O         


        

Answer 1

This answer provides a bit of clarity on where the numbers given in the answer by @Egis come from. (this will draw an upside down equilateral triangle and is written in kotlin)

class TriangleView(context: Context?, attrs: AttributeSet?) : View(context, attrs) {

    val paint = Paint()
    val path = Path()

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)
        canvas ?: return
        canvas.drawPath(configurePath(canvas.width.toFloat(), path), configurePaint(paint))
    }

    fun getHeight(width: Double): Float {
        return Math.sqrt((Math.pow(width, 2.0) - Math.pow((width / 2), 2.0))).toFloat()
    }

    fun configurePaint(paint: Paint): Paint {
        paint.color = android.graphics.Color.WHITE
        paint.isAntiAlias = true

        return paint
    }

    fun configurePath(width: Float, path: Path): Path {
        path.lineTo((width / 2f), getHeight(width.toDouble()))
        path.lineTo(width, 0F)
        path.lineTo(0f, 0f)

        return path
    }
}

The get height function is Pythagoras' Theorem and will always find the height of an equilateral triangle to be ~87% of its side length

Gist can be found here, it contains code for the other direction