Java OrientationHelper.getDecoratedStart方法代码示例

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private View findEndView(RecyclerView.LayoutManager layoutManager, OrientationHelper helper) {

    if (layoutManager instanceof LinearLayoutManager) {
      int lastChild = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();

      if (lastChild == RecyclerView.NO_POSITION) {
        return null;
      }

      View child = layoutManager.findViewByPosition(lastChild);

      if (helper.getDecoratedStart(child) + helper.getDecoratedMeasurement(child) / 2
          <= helper.getTotalSpace()) {
        return child;
      } else {
        if (((LinearLayoutManager) layoutManager).findFirstCompletelyVisibleItemPosition() == 0) {
          return null;
        } else {
          return layoutManager.findViewByPosition(lastChild - 1);
        }
      }
    }

    return super.findSnapView(layoutManager);
  }
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
/**
     * 当item位置变换，滚动recycler到正确的位置
     * TODO: 2017/2/21 0021 整理更优雅的写法  还有scrollToPosition(0)是否必要？
     */
    private void scrollToRightPositionWhenItemChanged(RecyclerView recyclerView, View itemView, int itemPos) {
        final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
        if (layoutManager instanceof ItemTouchHelper.ViewDropHandler) {
            OrientationHelper helper = OrientationHelper.createVerticalHelper(layoutManager);
            int start = helper.getDecoratedStart(itemView);
            int end = helper.getDecoratedEnd(itemView);
            ((LinearLayoutManager) layoutManager).scrollToPositionWithOffset(
                    itemPos, lastItemPos > itemPos ? start : end - itemViewHeight);
//                System.out.println(lastItemPos + "-" + childPos + "OrientationHelperOrientationHelper:"
//                        + height + "==" + itemViewHeight + "=||=" + start + "===" + end + "||||||" + myStart + "===" + itemTargetView.getHeight() );
        }
        if (lastItemPos == 0 || itemPos == 0) {
            recyclerView.scrollToPosition(0);
        }
    }
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private View findOneVisibleChild(int fromIndex, int toIndex, boolean completelyVisible,
                                 boolean acceptPartiallyVisible) {
    OrientationHelper helper;
    if (layoutManager.canScrollVertically()) {
        helper = OrientationHelper.createVerticalHelper(layoutManager);
    } else {
        helper = OrientationHelper.createHorizontalHelper(layoutManager);
    }

    final int start = helper.getStartAfterPadding();
    final int end = helper.getEndAfterPadding();
    final int next = toIndex > fromIndex ? 1 : -1;
    View partiallyVisible = null;
    for (int i = fromIndex; i != toIndex; i += next) {
        final View child = layoutManager.getChildAt(i);
        final int childStart = helper.getDecoratedStart(child);
        final int childEnd = helper.getDecoratedEnd(child);
        if (childStart < end && childEnd > start) {
            if (completelyVisible) {
                if (childStart >= start && childEnd <= end) {
                    return child;
                } else if (acceptPartiallyVisible && partiallyVisible == null) {
                    partiallyVisible = child;
                }
            } else {
                return child;
            }
        }
    }
    return partiallyVisible;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private int distanceToStart(View targetView, OrientationHelper helper, boolean fromEnd) {
    if (isRtlHorizontal && !fromEnd) {
        return distanceToEnd(targetView, helper, true);
    }

    return helper.getDecoratedStart(targetView) - helper.getStartAfterPadding();
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private int distanceToStart(View targetView, OrientationHelper helper, boolean fromEnd) {
    if (mIsRtlHorizontal && !fromEnd) {
        return distanceToEnd(targetView, helper, true);
    }

    return helper.getDecoratedStart(targetView) - helper.getStartAfterPadding();
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
@Override
public int computeAlignOffset(int offset, boolean isLayoutEnd,
                              boolean useAnchor, LayoutManagerHelper helper) {
    final boolean layoutInVertical = helper.getOrientation() == VERTICAL;
    final OrientationHelper orientationHelper = helper.getMainOrientationHelper();
    final View child = helper.findViewByPosition(offset + getRange().getLower());

    if (child == null) {
        return 0;
    }

    if (layoutInVertical) {
        // in middle nothing need to do
        if (isLayoutEnd) {
            if (offset == getItemCount() - 1) {
                //the last item may not have the largest bottom, so calculate gaps between last items in every lane
                return mMarginBottom + mPaddingBottom + (getMaxEnd(orientationHelper.getDecoratedEnd(child),
                    orientationHelper) - orientationHelper.getDecoratedEnd(child));
            } else if (!useAnchor) {
                final int minEnd = getMinEnd(orientationHelper.getDecoratedStart(child), orientationHelper);
                return minEnd - orientationHelper.getDecoratedEnd(child);
            }
        } else {
            if (offset == 0) {
                //the first item may not have the smallest top, so calculate gaps between first items in every lane
                return -mMarginTop - mPaddingTop - (orientationHelper.getDecoratedStart(child) - getMinStart(
                    orientationHelper.getDecoratedStart(child), orientationHelper));
            } else if (!useAnchor) {
                final int maxStart = getMaxStart(orientationHelper.getDecoratedEnd(child), orientationHelper);
                return maxStart - orientationHelper.getDecoratedStart(child);
            }
        }

    } else {

    }

    return 0;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
void calculateCachedStart(@NonNull OrientationHelper helper) {
    if (mViews.size() == 0) {
        mCachedStart = INVALID_LINE;
    } else {
        final View startView = mViews.get(0);
        mCachedStart = helper.getDecoratedStart(startView);
    }
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
/**
 * Returns if there is no child between start-end lines
 *
 * @param start The start line
 * @param end   The end line
 * @return true if a new child can be added between start and end
 */
boolean isEmpty(int start, int end, OrientationHelper orientationHelper) {
    final int count = mViews.size();
    for (int i = 0; i < count; i++) {
        final View view = mViews.get(i);
        if (orientationHelper.getDecoratedStart(view) < end &&
                orientationHelper.getDecoratedEnd(view) > start) {
            return false;
        }
    }
    return true;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private View findEndView(RecyclerView.LayoutManager layoutManager,
                         OrientationHelper helper) {

    if (layoutManager instanceof LinearLayoutManager) {
        int lastChild = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();

        if (lastChild == RecyclerView.NO_POSITION) {
            return null;
        }

        View child = layoutManager.findViewByPosition(lastChild);

        float visibleWidth;

        if (mIsRtlHorizontal) {
            visibleWidth = (float) helper.getDecoratedEnd(child)
                    / helper.getDecoratedMeasurement(child);
        } else {
            visibleWidth = (float) (helper.getTotalSpace() - helper.getDecoratedStart(child))
                    / helper.getDecoratedMeasurement(child);
        }

        // If we're at the start of the list, we shouldn't snap
        // to avoid having the first item not completely visible.
        boolean startOfList = ((LinearLayoutManager) layoutManager)
                .findFirstCompletelyVisibleItemPosition() == 0;

        if (visibleWidth > 0.5f && !startOfList) {
            return child;
        } else if (mSnapLastItemEnabled && startOfList) {
            return child;
        } else if (startOfList) {
            return null;
        } else {
            // If the child wasn't returned, we need to return the previous view
            return layoutManager.findViewByPosition(lastChild - 1);
        }
    }
    return null;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
/**
 * Return the child view that is currently closest to the center of this parent.
 *
 * @param layoutManager The {@link RecyclerView.LayoutManager} associated with the attached
 *                      {@link RecyclerView}.
 * @param helper        The relevant {@link OrientationHelper} for the attached {@link RecyclerView}.
 * @return the child view that is currently closest to the center of this parent.
 */
@Nullable
private View findCenterView(RecyclerView.LayoutManager layoutManager,
                            OrientationHelper helper) {
    int childCount = layoutManager.getChildCount();
    if (childCount == 0) {
        return null;
    }

    View closestChild = null;
    final int center;
    if (layoutManager.getClipToPadding()) {
        center = helper.getStartAfterPadding() + helper.getTotalSpace() / 2;
    } else {
        center = helper.getEnd() / 2;
    }
    int absClosest = Integer.MAX_VALUE;

    for (int i = 0; i < childCount; i++) {
        final View child = layoutManager.getChildAt(i);
        final int childMonthIndex = layoutManager.getPosition(child) % ITEM_PER_MONTH;
        if (childMonthIndex != ITEM_PER_MONTH / 2) {
            i += ITEM_PER_MONTH * (childMonthIndex > ITEM_PER_MONTH / 2 ? 1.5f : 0.5f) - childMonthIndex - 1;
            continue;
        }
        int childCenter = helper.getDecoratedStart(child)
                + (helper.getDecoratedMeasurement(child) / 2);
        int absDistance = Math.abs(childCenter - center);

        // if child center is closer than previous closest, set it as closest
        if (absDistance < absClosest) {
            absClosest = absDistance;
            closestChild = child;
        }
    }
    return closestChild;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
/**
 * Returns the first view that we should snap to.
 *
 * @param layoutManager the recyclerview's layout manager
 * @param helper        orientation helper to calculate view sizes
 * @return the first view in the LayoutManager to snap to
 */
private View findStartView(RecyclerView.LayoutManager layoutManager,
                           OrientationHelper helper) {

    if (layoutManager instanceof LinearLayoutManager) {
        int firstChild = ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();

        if (firstChild == RecyclerView.NO_POSITION) {
            return null;
        }

        View child = layoutManager.findViewByPosition(firstChild);

        float visibleWidth;

        // We should return the child if it's visible width
        // is greater than 0.5 of it's total width.
        // In a RTL configuration, we need to check the start point and in LTR the end point
        if (isRtlHorizontal) {
            visibleWidth = (float) (helper.getTotalSpace() - helper.getDecoratedStart(child))
                    / helper.getDecoratedMeasurement(child);
        } else {
            visibleWidth = (float) helper.getDecoratedEnd(child)
                    / helper.getDecoratedMeasurement(child);
        }

        // If we're at the end of the list, we shouldn't snap
        // to avoid having the last item not completely visible.
        boolean endOfList = ((LinearLayoutManager) layoutManager)
                .findLastCompletelyVisibleItemPosition()
                == layoutManager.getItemCount() - 1;

        if (visibleWidth > 0.5f && !endOfList) {
            return child;
        } else if (snapLastItem && endOfList) {
            return child;
        } else if (endOfList) {
            return null;
        } else {
            // If the child wasn't returned, we need to return
            // the next view close to the start.
            return layoutManager.findViewByPosition(firstChild + 1);
        }
    }

    return null;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
@Override
View findSnapView(RecyclerView.LayoutManager layoutManager) {
    OrientationHelper helper = layoutManager.canScrollHorizontally()
            ? OrientationHelper.createHorizontalHelper(layoutManager)
            : OrientationHelper.createVerticalHelper(layoutManager);
    int childCount = layoutManager.getChildCount();
    if (childCount == 0) return null;

    View closestChild = null;
    int closestPosition = RecyclerView.NO_POSITION;
    final int containerPosition = getContainerPosition(layoutManager, helper);
    int absClosest = Integer.MAX_VALUE;

    for (int i = 0; i < childCount; i++) {
        final View child = layoutManager.getChildAt(i);
        int childPosition = getChildPosition(child, helper);
        int absDistance = Math.abs(childPosition - containerPosition);
        if (helper.getDecoratedStart(child) == 0
                && previousClosestPosition != 0
                && layoutManager.getPosition(child) == 0) {
            //RecyclerView reached start
            closestChild = child;
            closestPosition = layoutManager.getPosition(closestChild);
            break;
        }
        if (helper.getDecoratedEnd(child) == helper.getTotalSpace()
                && previousClosestPosition != layoutManager.getItemCount() - 1
                && layoutManager.getPosition(child) == layoutManager.getItemCount() - 1) {
            //RecyclerView reached end
            closestChild = child;
            closestPosition = layoutManager.getPosition(closestChild);
            break;
        }
        if (previousClosestPosition == layoutManager.getPosition(child) && getDistance(layoutManager, child, helper) == 0) {
            //child is already set to the position.
            closestChild = child;
            break;
        }
        if (layoutManager.getPosition(child) % snapCount != 0) {
            continue;
        }
        if (absDistance < absClosest) {
            absClosest = absDistance;
            closestChild = child;
            closestPosition = layoutManager.getPosition(closestChild);
        }
    }
    previousClosestPosition = closestPosition == RecyclerView.NO_POSITION ? previousClosestPosition : closestPosition;
    isNoOffset = getDistance(layoutManager, closestChild, helper) == 0;
    if (listener != null && closestPosition != RecyclerView.NO_POSITION) {
        listener.snapped(closestPosition);
    }
    return closestChild;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private int distanceToEnd(View targetView, OrientationHelper helper) {
  if (mIsRtl) {
    return helper.getDecoratedStart(targetView) - helper.getStartAfterPadding();
  }
  return helper.getDecoratedEnd(targetView) - helper.getEndAfterPadding();
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
private View findEndView(RecyclerView.LayoutManager layoutManager,
                         OrientationHelper helper) {

    if (layoutManager instanceof LinearLayoutManager) {
        int lastChild = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
        int offset = 1;

        if (layoutManager instanceof GridLayoutManager) {
            offset += ((GridLayoutManager) layoutManager).getSpanCount() - 1;
        }

        if (lastChild == RecyclerView.NO_POSITION) {
            return null;
        }

        View child = layoutManager.findViewByPosition(lastChild);

        float visibleWidth;

        if (isRtlHorizontal) {
            visibleWidth = (float) helper.getDecoratedEnd(child)
                    / helper.getDecoratedMeasurement(child);
        } else {
            visibleWidth = (float) (helper.getTotalSpace() - helper.getDecoratedStart(child))
                    / helper.getDecoratedMeasurement(child);
        }

        // If we're at the start of the list, we shouldn't snap
        // to avoid having the first item not completely visible.
        boolean startOfList = ((LinearLayoutManager) layoutManager)
                .findFirstCompletelyVisibleItemPosition() == 0;

        if (visibleWidth > 0.5f && !startOfList) {
            return child;
        } else if (snapLastItem && startOfList) {
            return child;
        } else if (startOfList) {
            return null;
        } else {
            // If the child wasn't returned, we need to return the previous view
            return layoutManager.findViewByPosition(lastChild - offset);
        }
    }
    return null;
}
 

import android.support.v7.widget.OrientationHelper; //导入方法依赖的package包/类
/**
 * Returns the first view that we should snap to.
 *
 * @param layoutManager the recyclerview's layout manager
 * @param helper        orientation helper to calculate view sizes
 * @return the first view in the LayoutManager to snap to
 */
private View findStartView(RecyclerView.LayoutManager layoutManager,
                           OrientationHelper helper) {

    if (layoutManager instanceof LinearLayoutManager) {
        int firstChild = ((LinearLayoutManager) layoutManager).findFirstVisibleItemPosition();
        int offset = 1;

        if (layoutManager instanceof GridLayoutManager) {
            offset += ((GridLayoutManager) layoutManager).getSpanCount() - 1;
        }

        if (firstChild == RecyclerView.NO_POSITION) {
            return null;
        }

        View child = layoutManager.findViewByPosition(firstChild);

        float visibleWidth;

        // We should return the child if it's visible width
        // is greater than 0.5 of it's total width.
        // In a RTL configuration, we need to check the start point and in LTR the end point
        if (isRtlHorizontal) {
            visibleWidth = (float) (helper.getTotalSpace() - helper.getDecoratedStart(child))
                    / helper.getDecoratedMeasurement(child);
        } else {
            visibleWidth = (float) helper.getDecoratedEnd(child)
                    / helper.getDecoratedMeasurement(child);
        }

        // If we're at the end of the list, we shouldn't snap
        // to avoid having the last item not completely visible.
        boolean endOfList = ((LinearLayoutManager) layoutManager)
                .findLastCompletelyVisibleItemPosition()
                == layoutManager.getItemCount() - 1;

        if (visibleWidth > 0.5f && !endOfList) {
            return child;
        } else if (snapLastItem && endOfList) {
            return child;
        } else if (endOfList) {
            return null;
        } else {
            // If the child wasn't returned, we need to return
            // the next view close to the start.
            return layoutManager.findViewByPosition(firstChild + offset);
        }
    }

    return null;
}