如何在一个布局中拖放和缩放四个图像

Question

一个布局内有四个静态图像 使用以下代码无效。

 @Override
            public boolean onTouch(View v, MotionEvent event) {
                ImageView view = (ImageView) v;
                System.out.println("matrix=" + savedMatrix.toString());
                switch (event.getAction() & MotionEvent.ACTION_MASK) {
                    case MotionEvent.ACTION_DOWN:
                        savedMatrix.set(matrix);
                        startPoint.set(event.getX(), event.getY());
                        mode = DRAG;
                        break;
                    case MotionEvent.ACTION_POINTER_DOWN:
                        oldDist = spacing(event);
                        if (oldDist > 10f) {
                            savedMatrix.set(matrix);
                            midPoint(midPoint, event);
                            mode = ZOOM;
                        }
                        break;
                    case MotionEvent.ACTION_UP:
                    case MotionEvent.ACTION_POINTER_UP:
                        mode = NONE;
                        break;
                    case MotionEvent.ACTION_MOVE:
                        if (mode == DRAG) {
                            matrix.set(savedMatrix);
                            matrix.postTranslate(event.getX() - startPoint.x, event.getY() - startPoint.y);
                        } else if (mode == ZOOM) {
                            float newDist = spacing(event);
                            if (newDist > 10f) {
                                matrix.set(savedMatrix);
                                float scale = newDist / oldDist;
                                matrix.postScale(scale, scale, midPoint.x, midPoint.y);
                            }
                        }
                        break;
                }
                view.setImageMatrix(matrix);
                return true;
            }


            private float spacing(MotionEvent event) {
                float x = event.getX(0) - event.getX(1);
                float y = event.getY(0) - event.getY(1);
                return (float) Math.sqrt(x * x + y * y);
            }

            private void midPoint(PointF point, MotionEvent event) {
                float x = event.getX(0) + event.getX(1);
                float y = event.getY(0) + event.getY(1);

                point.set(x / 2, y / 2);
            }
        });