如何用两个手指平稳地移动视图

Question

我有一个其中包含recyclerView的视图。我想用两个手指移动这个视图。通过遵循官方文档this。这有助于我用一根手指移动视图。现在，我只想用两个手指移动视图。我已经阅读到可以通过实现MotionEvent.ACTION_POINTER_DOWN来实现，但是我不知道如何管理指针。下面是我的代码：

private View.OnTouchListener onTouchListener() {


        return new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                final int pointerIndex1,pointerIndex2;
                // Let the ScaleGestureDetector inspect all events.
                switch (event.getAction() & MotionEvent.ACTION_MASK) {
                    case MotionEvent.ACTION_DOWN: {
                        pointerIndex1 = event.getActionIndex();
                        final float x = event.getX(pointerIndex1);
                        final float y = event.getY(pointerIndex1);

                        // Remember where we started (for dragging)
                        mLastTouchX = x;
                        mLastTouchY = y;
                        // Save the ID of this pointer (for dragging)
                        mActivePointerId = event.getPointerId(0);
                        break;
                    }

                    case MotionEvent.ACTION_POINTER_DOWN:
                        pointerIndex2 = event.getActionIndex();
                    break;

                    case MotionEvent.ACTION_MOVE: {
                        // Find the index of the active pointer and fetch its position
                        final int pointerIndex = event.findPointerIndex(mActivePointerId);

                        final float x = event.getX(pointerIndex);
                        final float y = event.getY(pointerIndex);

                        // Calculate the distance moved
                        final float dx = x - mLastTouchX;
                        final float dy = y - mLastTouchY;

                        mPosX += dx;
                        mPosY += dy;

                        lin_container.setTranslationX(mPosX);
                        lin_container.setTranslationY(mPosY);

                        // Remember this touch position for the next move event
                        mLastTouchX = x;
                        mLastTouchY = y;

                        break;
                    }

                    case MotionEvent.ACTION_UP: {
                        mActivePointerId = INVALID_POINTER_ID;
                        break;
                    }

                    case MotionEvent.ACTION_CANCEL: {
                        mActivePointerId = INVALID_POINTER_ID;
                        break;
                    }

                    case MotionEvent.ACTION_POINTER_UP: {

                        final int pointerIndex = event.getActionIndex();
                        final int pointerId = event.getPointerId(pointerIndex);

                        if (pointerId == mActivePointerId) {
                            // This was our active pointer going up. Choose a new
                            // active pointer and adjust accordingly.
                            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                            mLastTouchX = event.getX(newPointerIndex);
                            mLastTouchY = event.getY(newPointerIndex);
                            mActivePointerId = event.getPointerId(newPointerIndex);
                        }
                        break;
                    }
                }
                return true;
            }
        };
    }

有人可以告诉我如何实现吗？

Answer 1

如果您想用两个手指移动视图[[仅，只需添加指针计数检查：

    final ImageView imageView;
    private float startX;
    private float startY;
    private float startTranslationX;
    private float startTranslationY;

    @Override
    public boolean onTouch(View view, MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {

            case MotionEvent.ACTION_DOWN: {
                startTranslationX = imageView.getTranslationX();
                startTranslationY = imageView.getTranslationY();

                startX = event.getX();
                startY = event.getY();
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                if (event.getPointerCount() == 2) {
                    imageView.setTranslationX(startTranslationX + event.getX() - startX);
                    imageView.setTranslationY(startTranslationY + event.getY() - startY);
                }
                break;
            }
        }

        return true;
    }