RecyclerView

来源：互联网发布：企业级sas软件多少钱编辑：程序博客网时间：2024/06/06 12:29

RecyclerView优秀文集

RecyclerView.ViewHolder

ViewHolder

RecyclerView.Adapter

LayoutManager

LinearLayoutManager

GridLayoutManager

StaggeredGridLayoutManager

LayoutManager

RecyclerView.ItemDecoration

RecyclerView.ItemAnimator

DefaultItemAnimator

ItemTouchHelper

SnapHelper

RecyclerView.RecycledViewPool

CursorAdapter

hold a CursorAdapter member in my recyclerView.Adapter implementation. Then passing all the handling of creating the new view & binding it to the cursor adapter

public class MyRecyclerAdapter extends Adapter<MyRecyclerAdapter.ViewHolder> {    // Because RecyclerView.Adapter in its current form doesn't natively     // support cursors, we wrap a CursorAdapter that will do all the job    // for us.    CursorAdapter mCursorAdapter;    Context mContext;    public MyRecyclerAdapter(Context context, Cursor c) {        mContext = context;        mCursorAdapter = new CursorAdapter(mContext, c, 0) {            @Override            public View newView(Context context, Cursor cursor, ViewGroup parent) {                // Inflate the view here            }            @Override            public void bindView(View view, Context context, Cursor cursor) {                // Binding operations            }        };    }    public static class ViewHolder extends RecyclerView.ViewHolder {        View v1;        public ViewHolder(View itemView) {            super(itemView);            v1 = itemView.findViewById(R.id.v1);        }    }    @Override    public int getItemCount() {        return mCursorAdapter.getCount();    }    @Override    public void onBindViewHolder(ViewHolder holder, int position) {        // Passing the binding operation to cursor loader        mCursorAdapter.getCursor().moveToPosition(position); //EDITED: added this line as suggested in the comments below, thanks :)        mCursorAdapter.bindView(holder.itemView, mContext, mCursorAdapter.getCursor());    }    @Override    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        // Passing the inflater job to the cursor-adapter        View v = mCursorAdapter.newView(mContext, mCursorAdapter.getCursor(), parent);        return new ViewHolder(v);    }}

SimpleCursorAdapter参数之谜

简书作者：zzh0838，原文链接：http://www.jianshu.com/p/daadc9d2bf1a

Question

SimpleCursorAdapter的构造函数是

SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags);

最后一个参数可选的值有：

FLAG_AUTO_REQUERY （这个值在Api 11 以后（包含）被弃用了，不用管）
FLAG_REGISTER_CONTENT_OBSERVER
0

那到底应该选哪一个呢（虽然只是二选一）？没错，我懵逼了。这个时候，当然是google来帮忙，stackOverFlow搜一搜，but，but，but，搜到的内容都很简略，没人告诉我，我在写SimpleCursorAdapter的时候应该传哪一个参数。

Answer

自己看源码喽,先看看继承继承关系吧（来至官方文档）：

java.lang.Object   ↳    android.widget.BaseAdapter        ↳    android.widget.CursorAdapter             ↳    android.widget.ResourceCursorAdapter                  ↳    android.widget.SimpleCursorAdapter

好吧，先看看SimpleCursorAdapter的默认构造函数吧

public SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from,            int[] to, int flags) {        super(context, layout, c, flags);        mTo = to;        mOriginalFrom = from;        findColumns(c, from);    }

可以看到flags传到了父类ResourceCursorAdapter的构造函数。那我们去看看吧。

public ResourceCursorAdapter(Context context, int layout, Cursor c, int flags) {        super(context, c, flags);        mLayout = mDropDownLayout = layout;        mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);        mDropDownInflater = mInflater;    }

flags又传到父类CursorAdapter了，再去看看：

public CursorAdapter(Context context, Cursor c, int flags){        init(context, c, flags);}

调用了init：

void init(Context context, Cursor c, int flags) {        if ((flags & FLAG_AUTO_REQUERY) == FLAG_AUTO_REQUERY) {            flags |= FLAG_REGISTER_CONTENT_OBSERVER;            mAutoRequery = true;        } else {            mAutoRequery = false;        }        boolean cursorPresent = c != null;        mCursor = c;        mDataValid = cursorPresent;        mContext = context;        mRowIDColumn = cursorPresent ? c.getColumnIndexOrThrow("_id") : -1;        if ((flags & FLAG_REGISTER_CONTENT_OBSERVER) == FLAG_REGISTER_CONTENT_OBSERVER) {            mChangeObserver = new ChangeObserver();            mDataSetObserver = new MyDataSetObserver();        } else {            mChangeObserver = null;            mDataSetObserver = null;        }        if (cursorPresent) {            if (mChangeObserver != null) c.registerContentObserver(mChangeObserver);            if (mDataSetObserver != null) c.registerDataSetObserver(mDataSetObserver);        }    }

函数有点长，假设我们的flags设置成了 0，不会有什么操作，假设我们的flags设置成了FLAG_REGISTER_CONTENT_OBSERVER，那么接下来会构造两个Observer:

mChangeObserver = new ChangeObserver();mDataSetObserver = new MyDataSetObserver();

并且在cursor不为null的时候将这两个Observer注册给cusor。

if (mChangeObserver != null) c.registerContentObserver(mChangeObserver);if (mDataSetObserver != null) c.registerDataSetObserver(mDataSetObserver);

那么问题来了，什么时候这两个Observer才会被触发呢？看看Cursor文档吧，文档了这么说的。

当调用方法requery()时，会触发ContentObserver。

当调用方法requery(), deactivate(), or close()时，DataSetObserver会被触发。

然后继续看文档，requery(), deactivate()都被弃用了。调用close后，cursor就没了（Closes the Cursor, releasing all of its resources and making it completely invalid.）。我尼玛，我尼玛，我尼玛，我心里一万只草泥马在奔腾，都不用看两个Observer定义的操作了。传这个参数压根就没什么鸟用。lz彻底懵逼了。

好了，现在可以下结论了：flag永远传0就可以了

0 0