Android：ListView 和RecyclerView区别

Posted 2020-12-17 比尔盖子殿下

缓存机制

 ListView的两级缓存

ListView的缓存和复用由它的父类AbsListView中的RecycleBin实现，设了两个缓存数组mActiveViews和mScrapViews。mActiveViews缓存显示在屏幕中的view，mScrapViews按ViewType缓存离屏的view

class RecycleBin {
    /**
     * The position of the first view stored in mActiveViews.
     */
    private int mFirstActivePosition;

    /**
     * Views that were on screen at the start of layout. This array is populated at the start of
     * layout, and at the end of layout all view in mActiveViews are moved to mScrapViews.
     * Views in mActiveViews represent a contiguous range of Views, with position of the first
     * view store in mFirstActivePosition.
     */
    private View[] mActiveViews = new View[0];

    /**
     * Unsorted views that can be used by the adapter as a convert view.
     */
    private ArrayList<View>[] mScrapViews;
}

 

 

 

 

RecyclerView的四级缓存

 RecyclerView的缓存和复用由Recycler实现，mAttachedScrap和mCachedViews的缓存方式跟ListView相似。mRecyclerPool是多个RecyclerView的复用池，mViewCacheExtension不直接使用，需要用户再定制，默认不实现。

public final class Recycler {
    final ArrayList<ViewHolder> mAttachedScrap = new ArrayList<>();
    final ArrayList<ViewHolder> mCachedViews = new ArrayList<ViewHolder>();
    RecycledViewPool mRecyclerPool;
    private ViewCacheExtension mViewCacheExtension;
}

 

 

 

缓存内容

1. ListView缓存View
2. RecyclerView缓存ViewHolder，抽象可理解为：View + ViewHolder(避免每次createView时调用findViewById)

总结

ListView二级缓存

 

RecyclerView四级缓存