Android 从库中选择图像时居中矩阵图像视图

我有一个ImageView，它显示了来自图库的图像，由于矩阵的缘故，该图像具有收缩到缩放的功能。这很好，但我希望它能做得更多。我想让它做的是在屏幕中心的图像被选中。我使用以下代码将其居中：

RectF drawableRect = new RectF(0, 0, options.outWidth, options.outHeight);
RectF viewRect = new RectF(0, 0, getBaseContext().getResources().getDisplayMetrics().widthPixels, getBaseContext().getResources().getDisplayMetrics().heightPixels);
matrix.setRectToRect(drawableRect, viewRect, Matrix.ScaleToFit.CENTER);

这可以正常工作，但它只有在用户触摸它之后才会集中，因此OnTouchListener的MotionEvent.ACTION\u DOWN方法：

imageView.setOnTouchListener(new OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                // TODO Auto-generated method stub

                ImageView view = (ImageView) v;
                dumpEvent(event);

                // Handle touch events here...
                switch (event.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    savedMatrix.set(matrix);
                    start.set(event.getX(), event.getY());
                    Log.d(TAG, "mode=DRAG");
                    mode = DRAG;
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    oldDist = spacing(event);
                    Log.d(TAG, "oldDist=" + oldDist);
                    if (oldDist > 10f) {
                        savedMatrix.set(matrix);
                        midPoint(mid, event);
                        mode = ZOOM;
                        Log.d(TAG, "mode=ZOOM");
                    }
                    break;
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_POINTER_UP:
                    mode = NONE;
                    Log.d(TAG, "mode=NONE");
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (mode == DRAG) {
                        // ...
                        matrix.set(savedMatrix);
                        matrix.postTranslate(event.getX() - start.x, event.getY()
                                - start.y);
                    } else if (mode == ZOOM) {
                        float newDist = spacing(event);
                        Log.d(TAG, "newDist=" + newDist);
                        if (newDist > 10f) {
                            matrix.set(savedMatrix);
                            float scale = newDist / oldDist;
                            matrix.postScale(scale, scale, mid.x, mid.y);
                        }
                    }
                    break;
                }

                view.setImageMatrix(matrix);
                return true;
            }

            private void dumpEvent(MotionEvent event) {
                String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE",
                        "POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };
                StringBuilder sb = new StringBuilder();
                int action = event.getAction();
                int actionCode = action & MotionEvent.ACTION_MASK;
                sb.append("event ACTION_").append(names[actionCode]);
                if (actionCode == MotionEvent.ACTION_POINTER_DOWN
                        || actionCode == MotionEvent.ACTION_POINTER_UP) {
                    sb.append("(pid ").append(
                            action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
                    sb.append(")");
                }
                sb.append("[");
                for (int i = 0; i < event.getPointerCount(); i++) {
                    sb.append("#").append(i);
                    sb.append("(pid ").append(event.getPointerId(i));
                    sb.append(")=").append((int) event.getX(i));
                    sb.append(",").append((int) event.getY(i));
                    if (i + 1 < event.getPointerCount())
                        sb.append(";");
                }
                sb.append("]");
                Log.d(TAG, sb.toString());
            }

            /** Determine the space between the first two fingers */
            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);
            }

            /** Calculate the mid point of the first two fingers */
            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);
            }
        });

---

当选择图像时，如何使矩阵居中？

不要重新发明轮子，使用这个

尝试在Touch上实现它，但我得到一个无法实例化类TouchImageView；没有空构造函数。我不明白你怎么称呼它的构造器？您可以直接将其放入布局XML中，或通过新的TouchImageViewContext对其进行实例化