ColorPickerView in Android

ColorPickerView in Android

public class ColorPickerView extends View {
    private Paint mPaint;
    private int[] mColors;
    private OnColorChangedListener mListener;

    public ColorPickerView(Context context) {
        super(context);
        init();
    }

    public ColorPickerView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

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

    private void init() {
        mColors = new int[] {
                0xFFFF0000, // red
                0xFF00FF00, // green
                0xFF0000FF, // blue
                0xFFFF00FF, // magenta
                0xFFFFFF00, // yellow
                0xFF00FFFF // cyan
        };
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setAntiAlias(true);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // set the view dimensions to be a square
        int width = MeasureSpec.getSize(widthMeasureSpec);
        int height = MeasureSpec.getSize(heightMeasureSpec);
        int size = Math.min(width, height);
        setMeasuredDimension(size, size);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        int width = getWidth();
        int height = getHeight();
        int colorCount = mColors.length;
        float arc = 360f / colorCount;
        RectF rectF = new RectF(0, 0, width, height);

        for (int i = 0; i < colorCount; i++) {
            mPaint.setColor(mColors[i]);
            canvas.drawArc(rectF, i * arc, arc, true, mPaint);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();
        int width = getWidth();
        int height = getHeight();
        int colorCount = mColors.length;
        float arc = 360f / colorCount;
        float centerX = width / 2f;
        float centerY = height / 2f;
        double angle = Math.atan2(y - centerY, x - centerX);
        angle = (angle < 0) ? (angle + 2 * Math.PI) : angle;
        int index = (int) (angle / arc);
        int color = mColors[index];

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                if (mListener != null) {
                    mListener.onColorChanged(color);
                }
                break;
            case MotionEvent.ACTION_UP:
                // do nothing
                break;
            default:
                return false;
        }

        return true;
    }

    public void setOnColorChangedListener(OnColorChangedListener listener) {
        mListener = listener;
    }

    public interface OnColorChangedListener {
        void onColorChanged(int color);
    }
}