class TPView(context: Context,attr:AttributeSet ) : View(context,attr) {


  private var preX: Float = 0.0f //上一次的觸摸點x坐標
  private var preY: Float = 0.0f //上一次觸摸點y坐標

  var mPath = Path()  //path路徑

  //畫筆
  private var mPaint = Paint(Paint.ANTI_ALIAS_FLAG or Paint.DITHER_FLAG)

  init {
    //畫筆為實心
    mPaint.style = Paint.Style.STROKE
    //顏色
    mPaint.color = Color.RED
    //筆觸為圓形
    mPaint.strokeCap = Paint.Cap.ROUND
    //畫筆大小
    mPaint.strokeWidth = 10f
    //View的背景顏色
    setBackgroundColor(Color.WHITE)
  }

  override fun onDraw(canvas: Canvas) {
    super.onDraw(canvas)
    //畫線
    canvas.drawPath(mPath,mPaint)
  }

  override fun onTouchEvent(event: MotionEvent): Boolean {

    when(event.action){
      MotionEvent.ACTION_DOWN -> { //手指按下的時候
        //將起始點移動到當前坐標
        mPath.moveTo(event.x,event.y)
        //記錄上次觸摸的坐標，注意ACTION_DOWN方法只會執(zhí)行一次
        preX = event.x
        preY = event.y
      }
      MotionEvent.ACTION_MOVE -> { //手指移動的時候

        //繪制圓滑曲線，即貝塞爾曲線,貝塞爾曲線這個知識自行了解
        mPath.quadTo(preX,preY,event.x,event.y)

        preX = event.x
        preY = event.y
      }
    }

    //重新繪制，會調用onDraw方法
    invalidate()
    return true
  }

}