有没有人有一个简单的解决方法来反转TwoWayView布局管理器的布局子项？
/*
* Copyright (C) 2014 Lucas Rocha
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.lucasr.twowayview.widget;
import android.graphics.Rect;
import org.lucasr.twowayview.TwoWayLayoutManager.Direction;
import org.lucasr.twowayview.TwoWayLayoutManager.Orientation;
class Lanes {
public static final int NO_LANE = -1;
private final BaseLayoutManager mLayout;
private final boolean mIsVertical;
private final Rect[] mLanes;
private final Rect[] mSavedLanes;
private final int mLaneSize;
private final Rect mTempRect = new Rect();
private final LaneInfo mTempLaneInfo = new LaneInfo();
private Integer mInnerStart;
private Integer mInnerEnd;
public static class LaneInfo {
public int startLane;
public int anchorLane;
public boolean isUndefined() {
return (startLane == NO_LANE || anchorLane == NO_LANE);
}
public void set(int startLane, int anchorLane) {
this.startLane = startLane;
this.anchorLane = anchorLane;
}
public void setUndefined() {
startLane = NO_LANE;
anchorLane = NO_LANE;
}
}
public Lanes(BaseLayoutManager layout, Orientation orientation, Rect[] lanes, int laneSize) {
mLayout = layout;
mIsVertical = (orientation == Orientation.VERTICAL);
mLanes = lanes;
mLaneSize = laneSize;
mSavedLanes = new Rect[mLanes.length];
for (int i = 0; i < mLanes.length; i++) {
mSavedLanes[i] = new Rect();
}
}
public Lanes(BaseLayoutManager layout, int laneCount) {
mLayout = layout;
mIsVertical = layout.isVertical();
mLanes = new Rect[laneCount];
mSavedLanes = new Rect[laneCount];
for (int i = 0; i < laneCount; i++) {
mLanes[i] = new Rect();
mSavedLanes[i] = new Rect();
}
mLaneSize = calculateLaneSize(layout, laneCount);
final int paddingLeft = layout.getPaddingLeft();
final int paddingTop = layout.getPaddingTop();
for (int i = 0; i < laneCount; i++) {
final int laneStart = i * mLaneSize;
final int l = paddingLeft + (mIsVertical ? laneStart : 0);
final int t = paddingTop + (mIsVertical ? 0 : laneStart);
final int r = (mIsVertical ? l + mLaneSize : l);
final int b = (mIsVertical ? t : t + mLaneSize);
mLanes[i].set(l, t, r, b);
}
}
public static int calculateLaneSize(BaseLayoutManager layout, int laneCount) {
if (layout.isVertical()) {
final int paddingLeft = layout.getPaddingLeft();
final int paddingRight = layout.getPaddingRight();
final int width = layout.getWidth() - paddingLeft - paddingRight;
return width / laneCount;
} else {
final int paddingTop = layout.getPaddingTop();
final int paddingBottom = layout.getPaddingBottom();
final int height = layout.getHeight() - paddingTop - paddingBottom;
return height / laneCount;
}
}
private void invalidateEdges() {
mInnerStart = null;
mInnerEnd = null;
}
public Orientation getOrientation() {
return (mIsVertical ? Orientation.VERTICAL : Orientation.HORIZONTAL);
}
public void save() {
for (int i = 0; i < mLanes.length; i++) {
mSavedLanes[i].set(mLanes[i]);
}
}
public void restore() {
for (int i = 0; i < mLanes.length; i++) {
mLanes[i].set(mSavedLanes[i]);
}
}
public int getLaneSize() {
return mLaneSize;
}
public int getCount() {
return mLanes.length;
}
private void offsetLane(int lane, int offset) {
mLanes[lane].offset(mIsVertical ? 0 : offset,
mIsVertical ? offset : 0);
}
public void offset(int offset) {
for (int i = 0; i < mLanes.length; i++) {
offset(i, offset);
}
invalidateEdges();
}
public void offset(int lane, int offset) {
offsetLane(lane, offset);
invalidateEdges();
}
public void getLane(int lane, Rect laneRect) {
laneRect.set(mLanes[lane]);
}
public int pushChildFrame(Rect outRect, int lane, int margin, Direction direction) {
final int delta;
final Rect laneRect = mLanes[lane];
if (mIsVertical) {
if (direction == Direction.END) {
delta = outRect.top - laneRect.bottom;
laneRect.bottom = outRect.bottom + margin;
} else {
delta = outRect.bottom - laneRect.top;
laneRect.top = outRect.top - margin;
}
} else {
if (direction == Direction.END) {
delta = outRect.left - laneRect.right;
laneRect.right = outRect.right + margin;
} else {
delta = outRect.right - laneRect.left;
laneRect.left = outRect.left - margin;
}
}
invalidateEdges();
return delta;
}
public void popChildFrame(Rect outRect, int lane, int margin, Direction direction) {
final Rect laneRect = mLanes[lane];
if (mIsVertical) {
if (direction == Direction.END) {
laneRect.top = outRect.bottom - margin;
} else {
laneRect.bottom = outRect.top + margin;
}
} else {
if (direction == Direction.END) {
laneRect.left = outRect.right - margin;
} else {
laneRect.right = outRect.left + margin;
}
}
invalidateEdges();
}
public void getChildFrame(Rect outRect, int childWidth, int childHeight, LaneInfo laneInfo,
Direction direction) {
final Rect startRect = mLanes[laneInfo.startLane];
// The anchor lane only applies when we're get child frame in the direction
// of the forward scroll. We'll need to rethink this once we start working on
// RTL support.
final int anchorLane =
(direction == Direction.END ? laneInfo.anchorLane : laneInfo.startLane);
final Rect anchorRect = mLanes[anchorLane];
if (mIsVertical) {
outRect.left = startRect.left;
outRect.top =
(direction == Direction.END ? anchorRect.bottom : anchorRect.top - childHeight);
} else {
outRect.top = startRect.top;
outRect.left =
(direction == Direction.END ? anchorRect.right : anchorRect.left - childWidth);
}
outRect.right = outRect.left + childWidth;
outRect.bottom = outRect.top + childHeight;
}
private boolean intersects(int start, int count, Rect r) {
for (int l = start; l < start + count; l++) {
if (Rect.intersects(mLanes[l], r)) {
return true;
}
}
return false;
}
private int findLaneThatFitsSpan(int anchorLane, int laneSpan, Direction direction) {
final int findStart = Math.max(0, anchorLane - laneSpan + 1);
final int findEnd = Math.min(findStart + laneSpan, mLanes.length - laneSpan + 1);
for (int l = findStart; l < findEnd; l++) {
mTempLaneInfo.set(l, anchorLane);
getChildFrame(mTempRect, mIsVertical ? laneSpan * mLaneSize : 1,
mIsVertical ? 1 : laneSpan * mLaneSize, mTempLaneInfo, direction);
if (!intersects(l, laneSpan, mTempRect)) {
return l;
}
}
return Lanes.NO_LANE;
}
public void findLane(LaneInfo outInfo, int laneSpan, Direction direction) {
outInfo.setUndefined();
int targetEdge = (direction == Direction.END ? Integer.MAX_VALUE : Integer.MIN_VALUE);
for (int l = 0; l < mLanes.length; l++) {
final int laneEdge;
if (mIsVertical) {
laneEdge = (direction == Direction.END ? mLanes[l].bottom : mLanes[l].top);
} else {
laneEdge = (direction == Direction.END ? mLanes[l].right : mLanes[l].left);
}
if ((direction == Direction.END && laneEdge < targetEdge) ||
(direction == Direction.START && laneEdge > targetEdge)) {
final int targetLane = findLaneThatFitsSpan(l, laneSpan, direction);
if (targetLane != NO_LANE) {
targetEdge = laneEdge;
outInfo.set(targetLane, l);
}
}
}
}
public void reset(Direction direction) {
for (int i = 0; i < mLanes.length; i++) {
final Rect laneRect = mLanes[i];
if (mIsVertical) {
if (direction == Direction.START) {
laneRect.bottom = laneRect.top;
} else {
laneRect.top = laneRect.bottom;
}
} else {
if (direction == Direction.START) {
laneRect.right = laneRect.left;
} else {
laneRect.left = laneRect.right;
}
}
}
invalidateEdges();
}
public void reset(int offset) {
for (int i = 0; i < mLanes.length; i++) {
final Rect laneRect = mLanes[i];
laneRect.offsetTo(mIsVertical ? laneRect.left : offset,
mIsVertical ? offset : laneRect.top);
if (mIsVertical) {
laneRect.bottom = laneRect.top;
} else {
laneRect.right = laneRect.left;
}
}
invalidateEdges();
}
public int getInnerStart() {
if (mInnerStart != null) {
return mInnerStart;
}
mInnerStart = Integer.MIN_VALUE;
for (int i = 0; i < mLanes.length; i++) {
final Rect laneRect = mLanes[i];
mInnerStart = Math.max(mInnerStart, mIsVertical ? laneRect.top : laneRect.left);
}
return mInnerStart;
}
public int getInnerEnd() {
if (mInnerEnd != null) {
return mInnerEnd;
}
mInnerEnd = Integer.MAX_VALUE;
for (int i = 0; i < mLanes.length; i++) {
final Rect laneRect = mLanes[i];
mInnerEnd = Math.min(mInnerEnd, mIsVertical ? laneRect.bottom : laneRect.right);
}
return mInnerEnd;
}
}
有趣的部分应该是：
public void getChildFrame(Rect outRect, int childWidth, int childHeight, LaneInfo laneInfo,
TwoWayLayoutManager.Direction direction) {
final Rect startRect = mLanes[laneInfo.startLane];
// The anchor lane only applies when we're get child frame in the direction
// of the forward scroll. We'll need to rethink this once we start working on
// RTL support.
final int anchorLane =
(direction == TwoWayLayoutManager.Direction.END ? laneInfo.anchorLane : laneInfo.startLane);
final Rect anchorRect = mLanes[anchorLane];
if (mIsVertical) {
outRect.left = startRect.left;
outRect.top =
(direction == TwoWayLayoutManager.Direction.END ? anchorRect.bottom : anchorRect.top - childHeight);
} else {
outRect.top = startRect.top;
outRect.left =
(direction == TwoWayLayoutManager.Direction.END ? anchorRect.right : anchorRect.left - childWidth);
}
outRect.right = outRect.left + childWidth;
outRect.bottom = outRect.top + childHeight;
}
其他参考资料：
谢谢！