Android 在onPostExecute中关闭光标不会显示任何内容

我使用AsyncTask从SQLite数据库加载数据，然后使用交错布局管理器和CustomListAdapter将数据提供给回收器视图

如果我在onPostExecuteMethod中不关闭doInBackground方法的游标，那么从上一个活动的转换是滞后的，android logcat说“跳过了52帧”

如果在Post Execute方法的末尾关闭游标，则不会出现延迟，但在活动内部不会呈现任何内容。（回收器视图不渲染任何内容。）

多因背景法 BaseAdapter类

导入android.content.Context；
导入android.database.Cursor；
导入android.database.DataSetObserver；
导入android.support.v7.widget.RecyclerView；
公共抽象类CursorRecyclServiceAdapter扩展了RecyclerView.Adapter{
私有上下文；
私有游标mCursor；
私有布尔mDataValid；
私有int-mRowIdColumn；
私有DataSetObserver mDataSetObserver；
公共游标RecyclServiceAdapter（上下文上下文，游标游标）{
mContext=上下文；
mCursor=光标；
mDataValid=cursor！=null；
mRowIdColumn=mDataValid？mCursor.getColumnIndex（“\u id”）：-1；
mDataSetObserver=new NotifyingDataSetObserver（）；
if（mCursor！=null）{
mCursor.registerDataSetObserver（mDataSetObserver）；
}
}
公共游标getCursor（）{
返回mCursor；
}
@凌驾
public int getItemCount（）{
if（mDataValid&&mCursor！=null）{
返回mCursor.getCount（）；
}
返回0；
}
@凌驾
公共长getItemId（int位置）{
if（mDataValid&&mCursor！=null&&mCursor.moveToPosition（位置））{
返回mCursor.getLong（mRowIdColumn）；
}
返回0；
}
@凌驾
公共void setHassTableId（布尔HassTableId）{
super.sethasstableId（true）；
}
BindViewHolder上的公共摘要无效（VH viewHolder，光标）；
@凌驾
公共无效onBindViewHolder（VH viewHolder，内部位置）{
如果（！mDataValid）{
抛出新的IllegalStateException（“仅当光标有效时才应调用它”）；
}
如果（！mCursor.moveToPosition（位置））{
抛出新的IllegalStateException（“无法将光标移动到位置”+位置）；
}
onBindViewHolder（viewHolder，mCursor）；
}
/**
*将基础游标更改为新游标。如果存在现有游标，则它将
*关闭。
*/
公共void changeCursor（游标）{
游标old=swapCursor（游标）；
如果（旧！=null）{
old.close（）；
}
}
/**
*交换新光标，返回旧光标。与
*{@link#changeCursor（Cursor）}，返回的旧游标不是
*关闭。
*/
公共游标交换游标（游标新建游标）{
if（newCursor==mCursor）{
返回null；
}
最终光标oldCursor=mCursor；
if（oldCursor！=null&&mDataSetObserver！=null）{
注销DataSetoObserver（mDataSetObserver）；
}
mCursor=newCursor；
if（mCursor！=null）{
if（mDataSetObserver！=null）{
mCursor.registerDataSetObserver（mDataSetObserver）；
}
mRowIdColumn=newCursor.getColumnIndexOrThrow（“\u id”）；
mDataValid=true；
notifyDataSetChanged（）；
}否则{
mRowIdColumn=-1；
mDataValid=false；
notifyDataSetChanged（）；
//RecyclerView.Adapter中没有NotifyDataSetionValidated（）方法
}
返回光标；
}
私有类NotifyingDataSetObserver扩展DataSetObserver{
@凌驾
更改后的公共无效（）{
super.onChanged（）；
mDataValid=true；
notifyDataSetChanged（）；
}
@凌驾
未验证的公共无效（）{
super.onInvalidated（）；
mDataValid=false；
notifyDataSetChanged（）；
//RecyclerView.Adapter中没有NotifyDataSetionValidated（）方法
}
}
}

扩展适配器类

导入android.content.Context；
导入android.content.Intent；
导入android.content.res.Resources；
导入android.database.Cursor；
导入android.graphics.Bitmap；
导入android.graphics.BitmapFactory；
导入android.graphics.Typeface；
导入android.os.AsyncTask；
导入android.support.v7.widget.CardView；
导入android.support.v7.widget.RecyclerView；
导入android.util.DisplayMetrics；
导入android.util.Log；
导入android.view.Display；
导入android.view.LayoutInflater；
导入android.view.view；
导入android.view.ViewGroup；
导入android.view.WindowManager；
导入android.widget.Button；
导入android.widget.LinearLayout；
导入android.widget.TextView；
公共类MyListCursorAdapter扩展了CursorRecyclServiceAdapter{
私有静态最终字符串TAG=“MyListCursorAdapter”；
公共MyListCursorAdapter（上下文，光标）{
超级（上下文、游标）；
}
@凌驾
public ViewHolder onCreateViewHolder（视图组父级，int-viewType）{
View itemView=LayoutInflater.from（parent.getContext（））
.充气（R.layout.productList，父项，false）；
ViewHolder vh=新的ViewHolder（项目视图）；
返回vh；
}
@凌驾
公共无效onBindViewHolder（最终视图持有人、最终光标）{
Book myListItem=Book.fromCursor（光标）；
viewHolder.titleTextView.setText（myListItem.getTitle（））；
viewHolder.shippingTextView.setText（myListItem.getAShipping（））；
d（标记“onBindViewHolder:+viewHolder.isRecyclable（））；
}
公共静态类ViewHolder扩展了RecyclerView.ViewHolder{
公共文本视图shippingTextView；
公共文本视图
 @Override
    protected void onPostExecute(Void Void) {             
        c.close();
        swipeRefreshLayout.setRefreshing(false);
        swipeRefreshLayout.setOnRefreshListener(
          new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                new MyTask().execute();
            }
        });
        swipeRefreshLayout.setColorSchemeColors(getResources().getIntArray(R.array.swipeRefreshColors));

    }

       try {           
                myDb = new SavedData(getApplicationContext());
                writeableDatabase = myDb.getReadableDatabase();
                final String[] projection = {SavedData.COLUMN_NAME_ENTRY_ID,
                        SavedData.COLUMN_NAME_PRICE,
                        SavedData.COLUMN_NAME_SHIPPING,
                        SavedData.COLUMN_NAME_WEIGHT,
                        SavedData.COLUMN_NAME_PRODUCT};
                sortOrder = BookSave.COLUMN_NAME_ENTRY_ID + " DESC";
                c = writeableDatabase.query(
                        SavedData.TABLE_NAME,  
                        projection,
                        null,
                        null,
                        null, 
                        null,
                        sortOrder
                );
                m = new MyListCursorAdapter(getApplicationContext(), c);
                gaggeredGridLayoutManager = new StaggeredGridLayoutManager(NUM, 1);

            } catch (Exception e) {
                e.printStackTrace();
            } finally {

            }

import android.content.Context;
import android.database.Cursor;
import android.database.DataSetObserver;
import android.support.v7.widget.RecyclerView;

public abstract class CursorRecyclerViewAdapter<VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {

    private Context mContext;

    private Cursor mCursor;

    private boolean mDataValid;

    private int mRowIdColumn;

    private DataSetObserver mDataSetObserver;

    public CursorRecyclerViewAdapter(Context context, Cursor cursor) {
        mContext = context;
        mCursor = cursor;
        mDataValid = cursor != null;
        mRowIdColumn = mDataValid ? mCursor.getColumnIndex("_id") : -1;
        mDataSetObserver = new NotifyingDataSetObserver();
        if (mCursor != null) {
            mCursor.registerDataSetObserver(mDataSetObserver);
        }
    }

    public Cursor getCursor() {
        return mCursor;
    }

    @Override
    public int getItemCount() {
        if (mDataValid && mCursor != null) {
            return mCursor.getCount();
        }
        return 0;
    }

    @Override
    public long getItemId(int position) {
        if (mDataValid && mCursor != null && mCursor.moveToPosition(position)) {
            return mCursor.getLong(mRowIdColumn);
        }
        return 0;
    }

    @Override
    public void setHasStableIds(boolean hasStableIds) {
        super.setHasStableIds(true);
    }

    public abstract void onBindViewHolder(VH viewHolder, Cursor cursor);

    @Override
    public void onBindViewHolder(VH viewHolder, int position) {
        if (!mDataValid) {
            throw new IllegalStateException("this should only be called when the cursor is valid");
        }
        if (!mCursor.moveToPosition(position)) {
            throw new IllegalStateException("couldn't move cursor to position " + position);
        }
        onBindViewHolder(viewHolder, mCursor);
    }

    /**
     * Change the underlying cursor to a new cursor. If there is an existing cursor it will be
     * closed.
     */
    public void changeCursor(Cursor cursor) {
        Cursor old = swapCursor(cursor);
        if (old != null) {
            old.close();
        }
    }

    /**
     * Swap in a new Cursor, returning the old Cursor.  Unlike
     * {@link #changeCursor(Cursor)}, the returned old Cursor is <em>not</em>
     * closed.
     */
    public Cursor swapCursor(Cursor newCursor) {
        if (newCursor == mCursor) {
            return null;
        }
        final Cursor oldCursor = mCursor;
        if (oldCursor != null && mDataSetObserver != null) {
            oldCursor.unregisterDataSetObserver(mDataSetObserver);
        }
        mCursor = newCursor;
        if (mCursor != null) {
            if (mDataSetObserver != null) {
                mCursor.registerDataSetObserver(mDataSetObserver);
            }
            mRowIdColumn = newCursor.getColumnIndexOrThrow("_id");
            mDataValid = true;
            notifyDataSetChanged();
        } else {
            mRowIdColumn = -1;
            mDataValid = false;
            notifyDataSetChanged();
            //There is no notifyDataSetInvalidated() method in RecyclerView.Adapter
        }
        return oldCursor;
    }

    private class NotifyingDataSetObserver extends DataSetObserver {
        @Override
        public void onChanged() {
            super.onChanged();
            mDataValid = true;
            notifyDataSetChanged();
        }

        @Override
        public void onInvalidated() {
            super.onInvalidated();
            mDataValid = false;
            notifyDataSetChanged();
            //There is no notifyDataSetInvalidated() method in RecyclerView.Adapter
        }
    }
}

import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Typeface;
import android.os.AsyncTask;
import android.support.v7.widget.CardView;
import android.support.v7.widget.RecyclerView;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Display;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;


public class MyListCursorAdapter extends CursorRecyclerViewAdapter<MyListCursorAdapter.ViewHolder> {

    private static final String TAG = "MyListCursorAdapter";

    public MyListCursorAdapter(Context context, Cursor cursor) {
        super(context, cursor);
    }


    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.productList, parent, false);
        ViewHolder vh = new ViewHolder(itemView);

        return vh;
    }

    @Override
    public void onBindViewHolder(final ViewHolder viewHolder, final Cursor cursor) {
        Book myListItem = Book.fromCursor(cursor);
        viewHolder.titleTextView.setText(myListItem.getTitle());
        viewHolder.shippingTextView.setText(myListItem.getAShipping());
        Log.d(TAG, "onBindViewHolder: "+viewHolder.isRecyclable());
    }



    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView shippingTextView;
        public TextView titleTextView;
        public LinearLayout insideCard;
        public Button payButton;
        public View seperator;
        public CardView cv;
        public View view;

        public ViewHolder(final View view) {
            super(view);
            WindowManager wm = (WindowManager) view.getContext().getSystemService(Context.WINDOW_SERVICE);
            Display display = wm.getDefaultDisplay();
            DisplayMetrics DM = new DisplayMetrics();
            display.getMetrics(DM);
            payButton = (Button) view.findViewById(R.id.readButton);
            seperator = view.findViewById(R.id.separator);
            titleTextView = (TextView) view.findViewById(R.id.titleTextView);
            insideCard = (LinearLayout) view.findViewById(R.id.insideCard);
            insideCard.getLayoutParams().width = (DM.widthPixels / 2) - 24;
            shippingTextView = (TextView) view.findViewById(R.id.shippingTextView);


//typeface
            Typeface light = Typeface.createFromAsset(titleTextView.getResources().getAssets(), "fonts/light.ttf");
            titleTextView.setTypeface(light);
            Typeface regular = Typeface.createFromAsset(authorTextView.getResources().getAssets(), "fonts/thinItalic.ttf");
            shippingTextView.setTypeface(regular);

            payButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent goToCheckout = new Intent(view.getContext(), ShowReader.class);
                    goToCheckout.putExtra("PRODUCT_NAME", titleTextView.getText());
                    view.getContext().startActivity(goToCheckout);
                }
            });


            setWidth((DM.widthPixels / 2) - 24);
        }

        public void setWidth(int a) {
            a = a - 8 * 4;
            payButton.getLayoutParams().width = a;
            seperator.getLayoutParams().width = a;

        }
    }

}

//typeface
            Typeface light = Typeface.createFromAsset(titleTextView.getResources().getAssets(), "fonts/light.ttf");
            titleTextView.setTypeface(light);
            Typeface regular = Typeface.createFromAsset(authorTextView.getResources().getAssets(), "fonts/thinItalic.ttf");
            shippingTextView.setTypeface(regular);

public class MyFontProvider {

    private static final String TAG = MyFontProvider.class.getSimpleName();

    private Map<String, Typeface> mCache;

    private static volatile MyFontProvider sInstance;

    public static MyFontProvider getInstance() {
        if (sInstance == null) {
            synchronized (MyFontProvider.class) {
                if (sInstance == null) {
                    sInstance = new MyFontProvider();
                }
            }
        }
        return sInstance;
    }

    private MyFontProvider() {
        mCache = new Hashtable<>();
    }

    public synchronized Typeface getFont(String assetPath, Context context) {
        if (!mCache.containsKey(assetPath)) {
            try {
                Typeface t = Typeface.createFromAsset(context.getAssets(), assetPath);
                mCache.put(assetPath, t);
            } catch (Exception e) {
                Log.e(TAG, "Error getting typeface (" + assetPath + " ) " + e.getMessage());
                return null;
            }
        }
        return mCache.get(assetPath);
    }
}

//typeface
            Typeface light = Typeface.createFromAsset(titleTextView.getResources().getAssets(), "fonts/light.ttf");
            titleTextView.setTypeface(light);
            Typeface regular = Typeface.createFromAsset(authorTextView.getResources().getAssets(), "fonts/thinItalic.ttf");
            shippingTextView.setTypeface(regular);

//typeface
            titleTextView.setTypeface(MyFontProvider.getInstance().getFont("fonts/light.ttf",this));
            shippingTextView.setTypeface(MyFontProvider.getInstance().getFont("fonts/thinItalic.ttf",this));