如何在屏幕边界android内实现可拖动的弹出窗口

Question

popupView.setOnTouchListener(new View.OnTouchListener() {
            int orgX, orgY;
            int offsetX, offsetY;

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        orgX = (int) event.getX();
                        orgY = (int) event.getY();
                        break;
                    case MotionEvent.ACTION_MOVE:
                        offsetX = (int)event.getRawX() - orgX;
                        offsetY = (int)event.getRawY() - orgY;
                        popupWindow.update(offsetX, offsetY, -1, -1, true);
                        break;
                }
                return true;
            }});

我已经实现了可拖动的弹出窗口，但是现在，我只想在屏幕内拖动。