Set an analog clock on time with gestures, touching minute hand clockwise or counter-clockwise

Question

I'm stuck trying to make a class that let users to set an analog clock on time. They have to move minute hand, not hour hand, clockwise or counter-clockwise in order to set the current time. Hour hand moves itself according minute hand progress, but I can't be able to move hour hand properly. It doesn't have a smooth movement every time goes through twelve o'clock and six o'clock, where there are angle critical points.

This is my workout until this moment. At twelve o'clock, angle is equal to 0 degrees, the minimum angle of course, and at six o'clock, angle is 180 degrees, the maximun angle. So, from twelve to six (clockwise), we have positive angles (0,180), and, from six to twelve (clockwise), we have negative angles (-180,0). That is ok, but if I want to calculate what will be the correct position of hour hand according with minute hand progress, I have to translate that angles to 0-360 degrees range.

Here is where I handle gestures:

@Override
public boolean onTouch(View v, MotionEvent event) {

    // Clock is the clock sphere and the minutes hand.
    final float xc = clock.getTranslationX() + (clock.getWidth() / 2);
    final float yc = clock.getTranslationY() + (clock.getHeight() / 2);

    final float x = event.getX();
    final float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        clock.clearAnimation();
        mMinutesCurrAngle = Math.toDegrees(Math.atan2(x - xc, yc - y));
        break;

    case MotionEvent.ACTION_MOVE:

        /**
         * Translate angles from [-179,179] to [0,360] to be able to move 
         * hours hand properly.
         */

        // Start Angle
        mMinutesCurrAngle = set360Angle(mMinutesCurrAngle);
        mMinutesPrevAngle = mMinutesCurrAngle;

        // Finish angle
        mMinutesCurrAngle = Math.toDegrees(Math.atan2(event.getX() - xc, yc - event.getY()));
        mMinutesCurrAngle = set360Angle(mMinutesCurrAngle);

        if ((mMinutesCurrAngle > mMinutesPrevAngle)) {
            // Clockwise between 12 and 6
            mHoursCurrAngle = mLastSpinHoursAngle + (mMinutesCurrAngle / 12);
        } else if ((mMinutesCurrAngle < mMinutesPrevAngle)) {
            // counter-Clockwise between 6 and 12
            mHoursCurrAngle = mLastSpinHoursAngle + (mMinutesCurrAngle / 12);
        } else if ((mMinutesCurrAngle > mMinutesPrevAngle) && (mMinutesCurrAngle < 0)) {
            // Clockwise between 6 and 12
            mHoursCurrAngle = mLastSpinHoursAngle + (- mMinutesCurrAngle / 12);
        } else if ((mMinutesCurrAngle < mMinutesPrevAngle) && (mMinutesCurrAngle < 0)) {
            // counter-Clockwise between 6 and 12
            mHoursCurrAngle = mLastSpinHoursAngle + (mMinutesCurrAngle / 12);
        }

        newSpin();

        // Transelate angles to the original format to represent them properly.
        mMinutesPrevAngle = translate360Angle(mMinutesPrevAngle);
        mMinutesCurrAngle = translate360Angle(mMinutesCurrAngle);

        animate(clock, mMinutesPrevAngle, mMinutesCurrAngle, 0);
        animate(hour, mHoursPrevAngle, mHoursCurrAngle, 0);
        mHoursPrevAngle = mHoursCurrAngle;
        break;

    case MotionEvent.ACTION_UP:
        break;        
    }
    return true;
}

Here is where I translate angles:

    /**
     * Translate angles from [-179,179] to [0,360] to be able to move 
     * hours hand properly.
     * @param minutesAngle
     * @return
     */
    private double set360Angle(double angle) {
        if (angle < 0) return (360 + angle); 
        else return angle;
    }

    /**
     * Transelate angles to the original format to represent them properly.
     * @param angle
     * @return
     */
    private double translate360Angle(double angle) {
        if (angle > 180) return (-360 + angle);
        else return angle;
    }

And here is where I know if minute hand starts a new spin:

private void newSpin() {

    if (translate360Angle(mMinutesPrevAngle) < 0 && translate360Angle(mMinutesCurrAngle) > 0) {
            // New Spin clockwise
            // I must remember hour hand angle
            mLastSpinHoursAngle = mHoursPrevAngle;
        } else if (translate360Angle(mMinutesPrevAngle) > 0 && translate360Angle(mMinutesCurrAngle) < 0) {
            // New Spin counter-clockwise
            // I must remember hour hand angle
            mLastSpinHoursAngle = mHoursPrevAngle;
        }
    }

Can anybody help me a litle bit? if anyone can help me, I promise to put your name to my first unborn daughter ... just kidding.

Answer 1

I discovered where the problem was...

The problem were the "if conditions" inside newSpin() method. Here, before check conditions, I translated angles to the original format (from 0 degrees to 180 degrees for twelve o'clock to six o'clock, clockwise, and from -180 degrees to 0 degrees, for six o'clock to twelve o'clock, clockwise too). So, instead check if user starts a new spin with minute hand, It was adding/subtracting a new spin everytime user goes through six o'clock instead twelve o'clock.

So, I did fix it modifying those conditions, and checking both minute hand angles, previous and current, on 360 degrees format. Now, if previous angle is bigger than 355 degrees and current angle is smaller than 5 degrees, I add a new spin to mSpinNumber. Likewise, if previous angle is smaller than 5 degrees and current angle is bigger than 355 degrees, I subtract a spin to mSpinNumber. I also did change method's name from newSpin() to calculateHourHandAngle().

private void calculateHourHandAngle() {

    if ((mMinutesPrevAngle > 355) && (mMinutesCurrAngle < 5)) {
        // New Spin clockwise
        mSpinNumber++;
    } else if ((mMinutesPrevAngle < 5) && (mMinutesCurrAngle > 355)) {
        // New Spin counter-clockwise
        mSpinNumber--;
    }
    mHoursCurrAngle = (mSpinNumber * (360/12)) + (mMinutesCurrAngle / 12);
}

I also get rid of unnecessary code in onTouch() method:

@Override
public boolean onTouch(View v, MotionEvent event) {

    // Clock is the clock sphere and the minutes hand.
    final float xc = clock.getTranslationX() + (clock.getWidth() / 2);
    final float yc = clock.getTranslationY() + (clock.getHeight() / 2);

    final float x = event.getX();
    final float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        clock.clearAnimation();
        hour.clearAnimation();
        mMinutesCurrAngle = Math.toDegrees(Math.atan2(x - xc, yc - y));
        break;

    case MotionEvent.ACTION_MOVE:

        /**
         * Translate angles from [-179,179] to [0,360] to be able to move 
         * hours hand properly.
         */

        // Start Angle
        mMinutesCurrAngle = set360Angle(mMinutesCurrAngle);
        mMinutesPrevAngle = mMinutesCurrAngle;

        // Finish angle
        mMinutesCurrAngle = Math.toDegrees(Math.atan2(event.getX() - xc, yc - event.getY()));
        mMinutesCurrAngle = set360Angle(mMinutesCurrAngle);

        calculateHourHandAngle();

        animate(clock, translate360Angle(mMinutesPrevAngle), translate360Angle(mMinutesCurrAngle), 0);
        animate(hour, mHoursPrevAngle, mHoursCurrAngle, 0);
        mHoursPrevAngle = mHoursCurrAngle;
        break;

    case MotionEvent.ACTION_UP:
        break;        
    }
    return true;
}

Now I be able to know what hour did set the user, because I know the initial position of hands clock, the number of spins and, the minute hand angle.