在Android项目中，我在公共类中有一些私有变量，警告消息不断提醒我实现getter和setter，而不是将值直接分配给这些私有变量。

什么时候应该为私有变量实现getter/setter？

MainActivity.java

public class MainActivity extends Activity implements OnTouchListener {
    // There are a few private variables that I used in the following methods in this class MainActivity
    private boolean _isMenuHidden = true;
    private boolean _isMenuMoveTriggered = false;
    private int _xDelta = 0;
    private int _yDelta = 0;
    private int _xTouchDown = 0;
    private int _yTouchDown = 0;
    private int _xPrevious = 0;
    private int _yPrevious = 0;

    // Some code omitted....

    // Implements View.OnTouchListener
    @Override
    public boolean onTouch(View view, MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();

        view = (View) view.getParent();
        LinearLayout.LayoutParams mLayoutParams = (LinearLayout.LayoutParams) view.getLayoutParams();

        switch (event.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                _xTouchDown = X;
                _yTouchDown = Y;
                _xPrevious = X;
                _yPrevious = Y;
                _xDelta = X - mLayoutParams.leftMargin;
                return false;
            // case MotionEvent.ACTION_DOWN:
            //break;
            case MotionEvent.ACTION_MOVE:
                if (((X - _xDelta) < -384) || ((X - _xDelta) > 0)) {
                // The move allows at most 480 * 80% = 384 pixels leftward and
                // zero pixels rightward
                } else {
                      // Some code omitted....
                  }
                break;

            // Some code omitted....

        } // switch ()
    } // End of public boolean onTouch()
    // Some code omitted....             
} // End of public class MainActivity