二階效果圖
控制點只有一個

    private float mStartPointX;
    private float mStartPointY;

    private float mEndPointX;
    private float mEndPointY;

    private float mFlagPointX;
    private float mFlagPointY;

    private Path mPath;

    private Paint mPaintBezier;
    private Paint mPaintFlag;
    private
 
 Paint mPaintFlagText;

    public SecondBezierView(Context context) {
        super(context);
    }

    public SecondBezierView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaintBezier = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaintBezier.setStrokeWidth(8);
        mPaintBezier.setStyle(Paint.Style.STROKE);

        mPaintFlag = new
 
 Paint(Paint.ANTI_ALIAS_FLAG);
        mPaintFlag.setStrokeWidth(3);
        mPaintFlag.setStyle(Paint.Style.STROKE);

        mPaintFlagText = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaintFlagText.setStyle(Paint.Style.STROKE);
        mPaintFlagText.setTextSize(20);
    }

    public SecondBezierView
 
(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mStartPointX = w / 4;
        mStartPointY = h / 2 - 200;

        mEndPointX = w * 3 / 4;
        mEndPointY = h / 2 - 200;

        mFlagPointX = w / 2;
        mFlagPointY = h / 2 - 300;

        mPath = new Path();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPath.reset();
        mPath.moveTo(mStartPointX, mStartPointY);
        mPath.quadTo(mFlagPointX, mFlagPointY, mEndPointX, mEndPointY);

        canvas.drawPoint(mStartPointX, mStartPointY, mPaintFlag);
        canvas.drawText("起點", mStartPointX, mStartPointY, mPaintFlagText);
        canvas.drawPoint(mEndPointX, mEndPointY, mPaintFlag);
        canvas.drawText("終點", mEndPointX, mEndPointY, mPaintFlagText);
        canvas.drawPoint(mFlagPointX, mFlagPointY, mPaintFlag);
        canvas.drawText("控制點", mFlagPointX, mFlagPointY, mPaintFlagText);
        canvas.drawLine(mStartPointX, mStartPointY, mFlagPointX, mFlagPointY, mPaintFlag);
        canvas.drawLine(mEndPointX, mEndPointY, mFlagPointX, mFlagPointY, mPaintFlag);

        canvas.drawPath(mPath, mPaintBezier);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_MOVE:
                mFlagPointX = event.getX();
                mFlagPointY = event.getY();
                invalidate();
                break;
        }
        return true;
    }