Android：ListView 和RecyclerView區別

緩存機制

 ListView的兩級緩存

ListView的緩存和復用由它的父類AbsListView中的RecycleBin實現，設了兩個緩存數組mActiveViews和mScrapViews。mActiveViews緩存顯示在屏幕中的view，mScrapViews按ViewType緩存離屏的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的四級緩存

 RecyclerView的緩存和復用由Recycler實現，mAttachedScrap和mCachedViews的緩存方式跟ListView相似。mRecyclerPool是多個RecyclerView的復用池，mViewCacheExtension不直接使用，需要用戶再定制，默認不實現。

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

 

 

 

緩存內容

1. ListView緩存View
2. RecyclerView緩存ViewHolder，抽象可理解為：View + ViewHolder(避免每次createView時調用findViewById)

總結

ListView二級緩存

 

RecyclerView四級緩存