RecyclerView顯示Item布局不一致
在自定義RecyclerAdapter的時(shí)候，在重寫onCreateViewHolder方法是使用了
@Override public H onCreateViewHolder(ViewGroup parent, int viewType) { View view=View.inflate(context,layoutId,null); return view; }進(jìn)行生成布局，結(jié)果發(fā)現(xiàn)生成的布局沒有LayoutParams。以前自定義View的時(shí)候發(fā)現(xiàn)，LayoutParams是由于ViewGroup生成的，因?yàn)檫@里添加的ViewGroup為null。所以并不會(huì)生成LayoutParams。結(jié)果在RecyclerView的getViewForPosition方法中檢查了有沒有LayoutParams如果沒有的話就調(diào)用LayoutManager的generateDefaultLayoutParams生成默認(rèn)的LayoutParames。代碼段如下：
final ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams(); final LayoutParams rvLayoutParams; if (lp == null) { rvLayoutParams = (LayoutParams) generateDefaultLayoutParams(); holder.itemView.setLayoutParams(rvLayoutParams); } else if (!checkLayoutParams(lp)) { rvLayoutParams = (LayoutParams) generateLayoutParams(lp); holder.itemView.setLayoutParams(rvLayoutParams); } else { rvLayoutParams = (LayoutParams) lp; }而在LinearLayoutManager中g(shù)enerateDefaultLayoutParams方法實(shí)現(xiàn)如下。
/** * {@inheritDoc} */ @Override public LayoutParams generateDefaultLayoutParams() { return new LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT); }最終會(huì)造成RecycleView的顯示效果與布局文件不一致。后來(lái)使用了LayoutInflater來(lái)填充布局。
@Override public H onCreateViewHolder(ViewGroup parent, int viewType) { View view = mInflater.inflate(layoutId, parent, false); return getInstanceOfH(view); }查看LayoutInflater源碼發(fā)現(xiàn)inflate最后的參數(shù)如果是false的話就不會(huì)將生成的View添加到parent。但是會(huì)根據(jù)parent產(chǎn)生相應(yīng)的LayoutParams 。源碼如下：
* @param attachToRoot Whether the inflated hierarchy should be attached to * the root parameter? If false, root is only used to create the * correct subclass of LayoutParams for the root view in the XML.
因?yàn)樵趏nCreateViewHolder中產(chǎn)生的View不能由我們手動(dòng)添加到RecycleView中所以最后的參數(shù)只能是false;
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