ColorPickerView.java 文件源码

private void drawAlphaPanel(Canvas canvas) {
    if (!mShowAlphaPanel || mAlphaRect == null || mAlphaPattern == null) {
        return;
    }

    final RectF rect = mAlphaRect;

    if (BORDER_WIDTH_PX > 0) {
        mBorderPaint.setColor(mBorderColor);
        canvas.drawRect(rect.left - BORDER_WIDTH_PX,
                rect.top - BORDER_WIDTH_PX,
                rect.right + BORDER_WIDTH_PX,
                rect.bottom + BORDER_WIDTH_PX,
                mBorderPaint);
    }

    mAlphaPattern.draw(canvas);

    float[] hsv = new float[] {
            mHue, mSat, mVal
    };
    int color = Color.HSVToColor(hsv);
    int acolor = Color.HSVToColor(0, hsv);

    mAlphaShader = new LinearGradient(rect.left, rect.top, rect.right, rect.top,
            color, acolor, TileMode.CLAMP);

    mAlphaPaint.setShader(mAlphaShader);

    canvas.drawRect(rect, mAlphaPaint);

    if (mAlphaSliderText != null && mAlphaSliderText != "") {
        canvas.drawText(mAlphaSliderText, rect.centerX(), rect.centerY() + 4 * mDensity,
                mAlphaTextPaint);
    }

    float rectWidth = 4 * mDensity / 2;
    Point p = alphaToPoint(mAlpha);

    RectF r = new RectF();
    r.left = p.x - rectWidth;
    r.right = p.x + rectWidth;
    r.top = rect.top - RECTANGLE_TRACKER_OFFSET;
    r.bottom = rect.bottom + RECTANGLE_TRACKER_OFFSET;

    canvas.drawRoundRect(r, 2, 2, mHueTrackerPaint);
}