无法在不同的活动android中拖动我的imageview

public class Drag extends SingleItemView implements View.OnTouchListener {

    private ImageView mImageView;
    private ViewGroup mRrootLayout;
    private int _xDelta;
    private int _yDelta;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.singleitemview);
        mRrootLayout = (ViewGroup) findViewById(R.id.root);
        mImageView = (ImageView)findViewById(R.id.image);

        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(350,350);
        mImageView.setLayoutParams(layoutParams);
        mImageView.setOnTouchListener(this);
    }

    public boolean onTouch(View view, MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                _xDelta = X - lParams.leftMargin;
                _yDelta = Y - lParams.topMargin;
                break;
            case MotionEvent.ACTION_UP:
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                break;
            case MotionEvent.ACTION_POINTER_UP:
                break;
            case MotionEvent.ACTION_MOVE:
                RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
                        .getLayoutParams();
                layoutParams.leftMargin = X - _xDelta;
                layoutParams.topMargin = Y - _yDelta;
                layoutParams.rightMargin = -250;
                layoutParams.bottomMargin = -250;
                view.setLayoutParams(layoutParams);
                break;
        }
        mRrootLayout.invalidate();
        return true;
    }
public class Drag extends SingleItemView implem