从左上角而不是左下角开始绘制

Question

我有以下课程：

internal class V(context: Context?) : View(context) {
    var path: Path = Path()
    var paint: Paint = Paint(Paint.ANTI_ALIAS_FLAG)
    var length: Float = 0f
    var intervals: FloatArray = floatArrayOf(0f, 0f)

    init {
        paint.color = Color.GREEN
        paint.style = Paint.Style.STROKE
        paint.strokeWidth = 20f
    }

    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        path.reset()
        val rect = RectF(0f, 0f, w.toFloat(), h.toFloat())
        val inset = paint.strokeWidth
        rect.inset(inset, inset)

        path.addRoundRect(rect, 100f, 100f, Path.Direction.CW)
        length = PathMeasure(path, false).length
        intervals[1] = length
        intervals[0] = intervals[1]
        val effect: PathEffect = DashPathEffect(intervals, length)
        paint.setPathEffect(effect)
    }

    fun setProgress(progress: Int) {
        val effect: PathEffect = DashPathEffect(intervals, length - length * progress / 100)
        paint.setPathEffect(effect)
        invalidate()
    }

    override fun onDraw(canvas: Canvas) {
        canvas.drawPath(path, paint)
    }
}

在我的

Activity#onCreate

中我可以这样使用：

val ll = LinearLayout(this)
ll.orientation = LinearLayout.VERTICAL
val sb = SeekBar(this)
ll.addView(sb)
val v = V(this)
ll.addView(v)
setContentView(ll)

val sbcl: SeekBar.OnSeekBarChangeListener = object : SeekBar.OnSeekBarChangeListener {
    override fun onProgressChanged(seekBar: SeekBar, progress: Int, fromUser: Boolean) {
        v.setProgress(progress)
    }

    override fun onStartTrackingTouch(seekBar: SeekBar) {}
    override fun onStopTrackingTouch(seekBar: SeekBar) {}
}
sb.setOnSeekBarChangeListener(sbcl)

现在，每当我拖动滑块时，边框都会从左下角绘制。如何使边框从左上角开始绘制？ （或任何其他点？）

Answer 1

我最终需要改变

onSizeChanged

方法，如下所示：

override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
    path.reset()
    val rect = RectF(0f, 0f, w.toFloat(), h.toFloat())
    val inset = paint.strokeWidth
    rect.inset(inset, inset)

    // minimum is 1 because 0 does not close rectangle.
    val radius = 1f


    // Starting from the top-left corner, move in a counter-clockwise direction to create the desired path
    path.moveTo(rect.left + radius, rect.top)
    path.lineTo(rect.right - radius, rect.top)
    path.arcTo(
        RectF(rect.right - radius * 2, rect.top, rect.right, rect.top + radius * 2),
        -90f,
        90f
    )
    path.lineTo(rect.right, rect.bottom - radius)
    path.arcTo(
        RectF(
            rect.right - radius * 2,
            rect.bottom - radius * 2,
            rect.right,
            rect.bottom
        ),
        0f,
        90f
    )
    path.lineTo(rect.left + radius, rect.bottom)
    path.arcTo(
        RectF(rect.left, rect.bottom - radius * 2, rect.left + radius * 2, rect.bottom),
        90f,
        90f
    )
    path.lineTo(rect.left, rect.top + radius)
    path.arcTo(
        RectF(rect.left, rect.top, rect.left + radius * 2, rect.top + radius * 2),
        180f,
        90f
    )
    path.close()

    length = PathMeasure(path, false).length
    intervals[1] = length
    intervals[0] = intervals[1]
    val effect: PathEffect = DashPathEffect(intervals, length)
    paint.setPathEffect(effect)
}