Java RecyclerView.getPaddingTop方法代码示例

import org.telegram.messenger.support.widget.RecyclerView; //导入方法依赖的package包/类
/**
 * Called when {@link #onMove(RecyclerView, ViewHolder, ViewHolder)} returns true.
 * <p>
 * ItemTouchHelper does not create an extra Bitmap or View while dragging, instead, it
 * modifies the existing View. Because of this reason, it is important that the View is
 * still part of the layout after it is moved. This may not work as intended when swapped
 * Views are close to RecyclerView bounds or there are gaps between them (e.g. other Views
 * which were not eligible for dropping over).
 * <p>
 * This method is responsible to give necessary hint to the LayoutManager so that it will
 * keep the View in visible area. For example, for LinearLayoutManager, this is as simple
 * as calling {@link LinearLayoutManager#scrollToPositionWithOffset(int, int)}.
 *
 * Default implementation calls {@link RecyclerView#scrollToPosition(int)} if the View's
 * new position is likely to be out of bounds.
 * <p>
 * It is important to ensure the ViewHolder will stay visible as otherwise, it might be
 * removed by the LayoutManager if the move causes the View to go out of bounds. In that
 * case, drag will end prematurely.
 *
 * @param recyclerView The RecyclerView controlled by the ItemTouchHelper.
 * @param viewHolder   The ViewHolder under user's control.
 * @param fromPos      The previous adapter position of the dragged item (before it was
 *                     moved).
 * @param target       The ViewHolder on which the currently active item has been dropped.
 * @param toPos        The new adapter position of the dragged item.
 * @param x            The updated left value of the dragged View after drag translations
 *                     are applied. This value does not include margins added by
 *                     {@link RecyclerView.ItemDecoration}s.
 * @param y            The updated top value of the dragged View after drag translations
 *                     are applied. This value does not include margins added by
 *                     {@link RecyclerView.ItemDecoration}s.
 */
public void onMoved(final RecyclerView recyclerView,
        final ViewHolder viewHolder, int fromPos, final ViewHolder target, int toPos, int x,
        int y) {
    final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
    if (layoutManager instanceof ViewDropHandler) {
        ((ViewDropHandler) layoutManager).prepareForDrop(viewHolder.itemView,
                target.itemView, x, y);
        return;
    }

    // if layout manager cannot handle it, do some guesswork
    if (layoutManager.canScrollHorizontally()) {
        final int minLeft = layoutManager.getDecoratedLeft(target.itemView);
        if (minLeft <= recyclerView.getPaddingLeft()) {
            recyclerView.scrollToPosition(toPos);
        }
        final int maxRight = layoutManager.getDecoratedRight(target.itemView);
        if (maxRight >= recyclerView.getWidth() - recyclerView.getPaddingRight()) {
            recyclerView.scrollToPosition(toPos);
        }
    }

    if (layoutManager.canScrollVertically()) {
        final int minTop = layoutManager.getDecoratedTop(target.itemView);
        if (minTop <= recyclerView.getPaddingTop()) {
            recyclerView.scrollToPosition(toPos);
        }
        final int maxBottom = layoutManager.getDecoratedBottom(target.itemView);
        if (maxBottom >= recyclerView.getHeight() - recyclerView.getPaddingBottom()) {
            recyclerView.scrollToPosition(toPos);
        }
    }
}