問題描述

如圖，讓和讓最新那條插入的數(shù)據(jù) 顯示在 頂部開始的地方，而舊的數(shù)據(jù)隱藏在頂部屏幕之外呢？

當(dāng)插入 問題14的時(shí)候，，前13條被隱藏在頂部之外的地方了。怎么做到這樣呢？模仿語(yǔ)言助手那種界面？如何做到

問題解答

以下兩種方案都親測(cè)可行：方案一：（無動(dòng)畫）

listView.setSelection(問題14的position);

方案二：（帶動(dòng)畫）

ListView lvBaseList添加問題14后調(diào)用

final int targetPosition = 2;//假設(shè)你要置頂?shù)腎temView的position = 2final long targetId = adapter.getItemId(targetPosition);View child = getTargetView(lvBaseList, targetId);final boolean isVisible = child != null;if (isVisible) {//問題14已顯示 Log.d(TAG, 'lvBaseList.onItemClick isVisible = true >> '); Log.d(TAG, 'lvBaseList.onItemClick lvBaseList.getY() = ' + (int) lvBaseList.getY()); Log.d(TAG, 'lvBaseList.onItemClick child.getY() = ' + (int) child.getY()); lvBaseList.smoothScrollBy((int) (child.getY() - lvBaseList.getY()), 200); return;}//問題14未顯示Log.d(TAG, 'lvBaseList.onItemClick isVisible = false >> ');lvBaseList.smoothScrollToPosition(targetPosition + lvBaseList.getHeaderViewsCount());lvBaseList.setOnScrollListener(new OnScrollListener() {@Override public void onScrollStateChanged(AbsListView view, int scrollState) {if (scrollState == SCROLL_STATE_IDLE) { lvBaseList.setOnScrollListener(null);//避免影響正常滾動(dòng) View child = getTargetView(lvBaseList, targetId); if (child == null) {Log.e(TAG, 'lvBaseList.onItemClick child == null >> return;');return; } Log.d(TAG, 'lvBaseList.onItemClick lvBaseList.getY() = ' + (int) lvBaseList.getY()); Log.d(TAG, 'lvBaseList.onItemClick child.getY() = ' + (int) child.getY());// lvBaseList.scrollListBy((int) (child.getY() - lvBaseList.getY()));//可行，無動(dòng)畫 lvBaseList.smoothScrollBy((int) (child.getY() - lvBaseList.getY()), 200);} }@Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { }});

需要用到的函數(shù)：

//根據(jù)targetId獲取childView private View getTargetView(ListView lvBaseList, long targetId) {View child = null;MomentView itemView;//MomentView相當(dāng)于ViewHolder，里面存放item數(shù)據(jù)或者itemIdMomentItem item;for (int i = 0; i < lvBaseList.getChildCount(); i++) { child = lvBaseList.getChildAt(i); itemView = child == null ? null : (MomentView) child.getTag(); item = itemView == null ? null : itemView.getData(); Log.d(TAG, 'lvBaseList.onItemClick item.getId() = ' + (item == null ? 0 : item.getId()) + '; targetId = ' + targetId); if (item != null && item.getId() == targetId) {Log.d(TAG, 'lvBaseList.onItemClick item != null && item.getId() == targetId >> break;');break; } child = null;}return child; }