关于android 2.3 source code中Listview layoutChildren() Method

Question

先贴上源码：
protected void layoutChildren() {
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if (dataChanged) {
                for (int i = 0; i < childCount; i++) {
                    recycleBin.addScrapView(getChildAt(i));
                    if (ViewDebug.TRACE_RECYCLER) {
                        ViewDebug.trace(getChildAt(i),
                                ViewDebug.RecyclerTraceType.MOVE_TO_SCRAP_HEAP, index, i);
                    }
                }
            } else {
                recycleBin.fillActiveViews(childCount, firstPosition);
            }
                           :
                           :
                           :
switch (mLayoutMode) {
            case LAYOUT_SET_SELECTION:
                if (newSel != null) {
                    sel = fillFromSelection(newSel.getTop(), childrenTop, childrenBottom);
                } else {
                    sel = fillFromMiddle(childrenTop, childrenBottom);
                }
                break;
            case LAYOUT_SYNC:
                sel = fillSpecific(mSyncPosition, mSpecificTop);
                break;
            case LAYOUT_FORCE_BOTTOM:
                sel = fillUp(mItemCount - 1, childrenBottom);
                adjustViewsUpOrDown();
                break;
            case LAYOUT_FORCE_TOP:
                mFirstPosition = 0;
                sel = fillFromTop(childrenTop);
                adjustViewsUpOrDown();
                break;
            case LAYOUT_SPECIFIC:
                sel = fillSpecific(reconcileSelectedPosition(), mSpecificTop);
                break;
            case LAYOUT_MOVE_SELECTION:
                sel = moveSelection(oldSel, newSel, delta, childrenTop, childrenBottom);
                break;
            default:
                if (childCount == 0) {
                    if (!mStackFromBottom) {
                        final int position = lookForSelectablePosition(0, true);
                        setSelectedPositionInt(position);
                        sel = fillFromTop(childrenTop);
                    } else {
                        final int position = lookForSelectablePosition(mItemCount - 1, false);
                        setSelectedPositionInt(position);
                        sel = fillUp(mItemCount - 1, childrenBottom);
                    }
                } else {
                    if (mSelectedPosition >= 0 && mSelectedPosition < mItemCount) {
                        sel = fillSpecific(mSelectedPosition,
                                oldSel == null ? childrenTop : oldSel.getTop());
                    } else if (mFirstPosition < mItemCount) {
                        sel = fillSpecific(mFirstPosition,
                                oldFirst == null ? childrenTop : oldFirst.getTop());
                    } else {
                        sel = fillSpecific(0, childrenTop);
                    }
                }
                break;
            }            // Flush any cached views that did not get reused above
            recycleBin.scrapActiveViews();在上面的几个case中，都会调用makeAndAddView（）method，然后在这个method中调用RecycleBin中的getActiveView（） method把之前If语句中fillActiveViews的active view给draw到window上。但是当完成listview的show之后，立刻调用recycleBin.scrapActiveViews()清除了所有的active view，这样岂不是list item刚花完就给delete掉了，这样还怎么显示啊？？我知道我必然是理解出错了，但是不知道错在那里，跪求看过Listview layoutChildren()的大大们给解释。

Answer 1

who can help me？？？

Answer 2

个人理解，画在屏幕上的是View的bitmap cache，并不是view本身。另外scrapActiveViews的注释是Flush any cached views that did not get reused above，至少把不用的View flush掉，并不是删除所有的View吧。个人理解而已，不是权威答案。