Gallery3D中画图时调用glTranslate函数参数赋值过程

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GridDrawManager::drawDisplayItem(RenderView view, GL11 gl, DisplayItem displayItem, Texture texture, int pass,Texture previousTexture, float mixRatio) 函数有下面几句：

Vector3f animatedPosition = displayItem.mAnimatedPosition;
float translateXf = animatedPosition.x * camera.mOneByScale;
float translateYf = animatedPosition.y * camera.mOneByScale;
float translateZf = -animatedPosition.z;

调用过程：
->computeVisibleItems(),displayItems[baseIndex + j] = displayItem;Vector3f position = pool.create(); GridCameraManager.getSlotPositionForSlotIndex(i, camera, layout, deltaAnchorPosition, position);//give position value displayList.setPositionAndStackIndex(displayItem, position, j, true);//raletive position to item

->GridLayer, mDrawManager = new GridDrawManager(context, mCamera, mDrawables, sDisplayList, sDisplayItems, sDisplaySlots);
->GridDrawManager(), mDisplayItems = displayItems;
->drawFocusItems ,DisplayItem[] displayItems = mDisplayItems;
->animatedPosition = displayItem.mAnimatedPosition;
->drawDisplayItem, amAnimatedPosition
->DisplayItem::commit() amAnimatedPosition.set(mTargetPosition);
-> DisplayItem::set(Vector3f position, int stackIndex, boolean performTransition) mTargetPosition.z =

public void getPositionForSlotIndex(int slotIndex, int itemWidth, int itemHeight, Vector3f outPosition) {
outPosition.x = (slotIndex / mNumRows) * (itemWidth + mSpacingX);
outPosition.y = (slotIndex % mNumRows) * (itemHeight + mSpacingY);
int maxY = (mNumRows - 1) * (itemHeight + mSpacingY);
outPosition.y -= (maxY >> 1);
outPosition.z = 0;
Log.d("outPosition","slotIndex="+slotIndex+",mNumRows="+mNumRows+",outPosition=("+outPosition.x+","+outPosition.y+","+outPosition.z+")");
}

在gallery3d中矩阵是从上到下、从左到右排列的，在主界面时最多有3行，mNumRows＝3，在缩略图界面最多4行mNumRows＝4，在查看界面只有一行mNumRows＝1
上面函数是计算所绘制项位置的，slotIndex / mNumRows得到的是当前处于多少列，slotIndex % mNumRows得到的是处于多少行。 int maxY = (mNumRows - 1) * (itemHeight + mSpacingY);
outPosition.y -= (maxY >> 1);是为了在y方向对称，想成屏幕中间是分界线，以上的项y为负，线以下的y为正。
deltaAnchorPosition的赋值过程：

int currentlyVisibleSlotIndex = getAnchorSlotIndex(ANCHOR_CENTER);->anchorItem = displayItem.mItemRef;-> newSlotIndex = i;->if (currentAnchorSlotIndex != Shared.INVALID && newAnchorSlotIndex != Shared.INVALID) {
layout.getPositionForSlotIndex(newAnchorSlotIndex, itemWidth, itemHeight, deltaAnchorPosition);
oldLayout.getPositionForSlotIndex(currentAnchorSlotIndex, itemWidth, itemHeight, currentSlotPosition);
currentSlotPosition.subtract(sDeltaAnchorPosition);
deltaAnchorPosition.subtract(currentSlotPosition);
deltaAnchorPosition.y = 0;
deltaAnchorPosition.z = 0;
}

MediaFeed::run()
onFeedChanged(, onLayout(newSlotIndex, currentlyVisibleSlotIndex, null);
onLayout, sDeltaAnchorPositionUncommited.set(deltaAnchorPosition);
computeVisibleRange(),sDeltaAnchorPosition.set(sDeltaAnchorPositionUncommited);
deltaAnchorPosition.set(sDeltaAnchorPosition);
deltaAnchorPosition