android - 安卓如何让View往屏幕外隐藏？

问题描述

如图，让和让最新那条插入的数据 显示在 顶部开始的地方，而旧的数据隐藏在顶部屏幕之外呢？

当插入 问题14的时候，，前13条被隐藏在顶部之外的地方了。怎么做到这样呢？模仿语言助手那种界面？如何做到

问题解答

以下两种方案都亲测可行：方案一：（无动画）

listView.setSelection(问题14的position);

方案二：（带动画）

ListView lvBaseList添加问题14后调用

final int targetPosition = 2;//假设你要置顶的ItemView的position = 2final long targetId = adapter.getItemId(targetPosition);View child = getTargetView(lvBaseList, targetId);final boolean isVisible = child != null;if (isVisible) {//问题14已显示 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;}//问题14未显示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);//避免影响正常滚动 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，无动画 lvBaseList.smoothScrollBy((int) (child.getY() - lvBaseList.getY()), 200);} }@Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { }});

需要用到的函数：

//根据targetId获取childView private View getTargetView(ListView lvBaseList, long targetId) {View child = null;MomentView itemView;//MomentView相当于ViewHolder，里面存放item数据或者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; }