支持RecyclerView的CursorAdapter的RecyclerViewCursorAdapter

github开源代码 点击打开链接，能够支持在RecyclerView上使用CursorAdapter，同时结合android Loader框架更加效率的加载Android本地数据库数据。

主要依靠下面两个类，RecyclerViewCursorAdapter和CursorFilter，使用方法和在ListView或GridView中一样。

一、方法

使用方法可参考 点击打开链接 其中介绍了在 ListView / GridView 中使用 CursorAdapter，并结合 android Loader 框架的使用。

下面简单介绍一下 RecyclerView 相应的使用：

1. 初始化时，首先构造一个传入参数 Cursor 为 null 的 RecyclerViewCursorAdapter，将其绑定到 RecyclerView 上面

2. 在LoaderManager.LoaderCallbacks 的 onCreateLoader 方法中构造需要的 CursorLoader

3. 在LoaderManager.LoaderCallbacks 的 onLoadFinish 方法中调用 RecyclerViewCursorAdapter#swapAdapter(Cursor) 将获取到的 Cursor 传入，RecyclerViewCursorAdapter 会自动根据新的 Cursor 刷新

4. 在LoaderManager.LoaderCallbacks 的 onLoadReset 方法中调用 RecyclerViewCursorAdapter#swapAdapter(null)

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Copyright (C) 2014 [email protected]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

import android.content.Context;
import android.database.ContentObserver;
import android.database.Cursor;
import android.database.DataSetObserver;
import android.os.Handler;
import android.support.v7.widget.RecyclerView;
import android.widget.Filter;
import android.widget.FilterQueryProvider;
import android.widget.Filterable;

/**
 * Version 1.0
 * 

 * Date: 2014-07-07 19:53
 * Author: [email protected]
 * 

 * Copyright © 2009-2014 LiGux.com.
 */
public abstract class RecyclerViewCursorAdapter<VH extends RecyclerView.ViewHolder>
        extends RecyclerView.Adapter<VH>
        implements Filterable, CursorFilter.CursorFilterClient {

    /**
     * Call when bind view with the cursor
     *
     * @param holder
     * @param cursor
     */
    public abstract void onBindViewHolder(VH holder, Cursor cursor);

    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected boolean mDataValid;

    /**
     * The current cursor
     */
    protected Cursor mCursor;

    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected Context mContext;

    /**
     * The row id column
     */
    protected int mRowIDColumn;

    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected ChangeObserver mChangeObserver;

    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected DataSetObserver mDataSetObserver;

    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected CursorFilter mCursorFilter;

    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected FilterQueryProvider mFilterQueryProvider;

    /**
     * If set the adapter will register a content observer on the cursor and will call
     * {@link #onContentChanged()} when a notification comes in.  Be careful when
     * using this flag: you will need to unset the current Cursor from the adapter
     * to avoid leaks due to its registered observers.  This flag is not needed
     * when using a CursorAdapter with a
     * {@link android.content.CursorLoader}.
     */
    public static final int FLAG_REGISTER_CONTENT_OBSERVER = 0x02;

    /**
     * Recommended constructor.
     *
     * @param c       The cursor from which to get the data.
     * @param context The context
     * @param flags   Flags used to determine the behavior of the adapter;
     *                Currently it accept {@link #FLAG_REGISTER_CONTENT_OBSERVER}.
     */
    public RecyclerViewCursorAdapter(Context context, Cursor c, int flags) {
        init(context, c, flags);
    }

    void init(Context context, Cursor c, int flags) {

        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);
        }
        setHasStableIds(true);
    }

    /**
     * Returns the cursor.
     *
     * @return the cursor.
     */
    @Override
    public Cursor getCursor() {
        return mCursor;
    }

    /**
     * @see android.support.v7.widget.RecyclerView.Adapter#getItemCount()
     */
    @Override
    public int getItemCount() {
        if (mDataValid && mCursor != null) {
            return mCursor.getCount();
        } else {
            return 0;
        }
    }

    /**
     * @param position Adapter position to query
     *
     * @return
     *
     * @see android.support.v7.widget.RecyclerView.Adapter#getItemId(int)
     */
    @Override
    public long getItemId(int position) {
        if (mDataValid && mCursor != null) {
            if (mCursor.moveToPosition(position)) {
                return mCursor.getLong(mRowIDColumn);
            } else {
                return 0;
            }
        } else {
            return 0;
        }
    }

    @Override
    public void onBindViewHolder(VH holder, 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(holder, mCursor);
    }

    /**
     * Change the underlying cursor to a new cursor. If there is an existing cursor it will be
     * closed.
     *
     * @param cursor The new cursor to be used
     */
    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 not
     * closed.
     *
     * @param newCursor The new cursor to be used.
     *
     * @return Returns the previously set Cursor, or null if there wasa not one.
     * If the given new Cursor is the same instance is the previously set
     * Cursor, null is also returned.
     */
    public Cursor swapCursor(Cursor newCursor) {
        if (newCursor == mCursor) {
            return null;
        }
        Cursor oldCursor = mCursor;
        if (oldCursor != null) {
            if (mChangeObserver != null) oldCursor.unregisterContentObserver(mChangeObserver);
            if (mDataSetObserver != null) oldCursor.unregisterDataSetObserver(mDataSetObserver);
        }
        mCursor = newCursor;
        if (newCursor != null) {
            if (mChangeObserver != null) newCursor.registerContentObserver(mChangeObserver);
            if (mDataSetObserver != null) newCursor.registerDataSetObserver(mDataSetObserver);
            mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
            mDataValid = true;
            // notify the observers about the new cursor
            notifyDataSetChanged();
        } else {
            mRowIDColumn = -1;
            mDataValid = false;
            // notify the observers about the lack of a data set
            notifyDataSetChanged();
//            notifyDataSetInvalidated();
        }
        return oldCursor;
    }

    /**
     * 
Converts the cursor into a CharSequence. Subclasses should override this
     * method to convert their results. The default implementation returns an
     * empty String for null values or the default String representation of
     * the value.

     *
     * @param cursor the cursor to convert to a CharSequence
     *
     * @return a CharSequence representing the value
     */
    public CharSequence convertToString(Cursor cursor) {
        return cursor == null ? "" : cursor.toString();
    }

    /**
     * Runs a query with the specified constraint. This query is requested
     * by the filter attached to this adapter.
     * 

     * The query is provided by a
     * {@link android.widget.FilterQueryProvider}.
     * If no provider is specified, the current cursor is not filtered and returned.
     * 

     * After this method returns the resulting cursor is passed to {@link #changeCursor(Cursor)}
     * and the previous cursor is closed.
     * 

     * This method is always executed on a background thread, not on the
     * application's main thread (or UI thread.)
     * 

     * Contract: when constraint is null or empty, the original results,
     * prior to any filtering, must be returned.
     *
     * @param constraint the constraint with which the query must be filtered
     *
     * @return a Cursor representing the results of the new query
     *
     * @see #getFilter()
     * @see #getFilterQueryProvider()
     * @see #setFilterQueryProvider(android.widget.FilterQueryProvider)
     */
    public Cursor runQueryOnBackgroundThread(CharSequence constraint) {
        if (mFilterQueryProvider != null) {
            return mFilterQueryProvider.runQuery(constraint);
        }

        return mCursor;
    }

    public Filter getFilter() {
        if (mCursorFilter == null) {
            mCursorFilter = new CursorFilter(this);
        }
        return mCursorFilter;
    }

    /**
     * Returns the query filter provider used for filtering. When the
     * provider is null, no filtering occurs.
     *
     * @return the current filter query provider or null if it does not exist
     *
     * @see #setFilterQueryProvider(android.widget.FilterQueryProvider)
     * @see #runQueryOnBackgroundThread(CharSequence)
     */
    public FilterQueryProvider getFilterQueryProvider() {
        return mFilterQueryProvider;
    }

    /**
     * Sets the query filter provider used to filter the current Cursor.
     * The provider's
     * {@link android.widget.FilterQueryProvider#runQuery(CharSequence)}
     * method is invoked when filtering is requested by a client of
     * this adapter.
     *
     * @param filterQueryProvider the filter query provider or null to remove it
     *
     * @see #getFilterQueryProvider()
     * @see #runQueryOnBackgroundThread(CharSequence)
     */
    public void setFilterQueryProvider(FilterQueryProvider filterQueryProvider) {
        mFilterQueryProvider = filterQueryProvider;
    }

    /**
     * Called when the {@link ContentObserver} on the cursor receives a change notification.
     * The default implementation provides the auto-requery logic, but may be overridden by
     * sub classes.
     *
     * @see ContentObserver#onChange(boolean)
     */
    protected abstract void onContentChanged();

    private class ChangeObserver extends ContentObserver {

        public ChangeObserver() {
            super(new Handler());
        }

        @Override
        public boolean deliverSelfNotifications() {
            return true;
        }

        @Override
        public void onChange(boolean selfChange) {
            onContentChanged();
        }
    }

    private class MyDataSetObserver extends DataSetObserver {

        @Override
        public void onChanged() {
            mDataValid = true;
            notifyDataSetChanged();
        }

        @Override
        public void onInvalidated() {
            mDataValid = false;
            notifyDataSetChanged();
//            notifyDataSetInvalidated();
        }
    }
}

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.database.Cursor;
import android.widget.Filter;

/**
 * The CursorFilter delegates most of the work to the
 * {@link android.widget.CursorAdapter}. Subclasses should override these
 * delegate methods to run the queries and convert the results into String
 * that can be used by auto-completion widgets.
 */
class CursorFilter extends Filter {

    CursorFilterClient mClient;

    interface CursorFilterClient {

        CharSequence convertToString(Cursor cursor);

        Cursor runQueryOnBackgroundThread(CharSequence constraint);

        Cursor getCursor();

        void changeCursor(Cursor cursor);
    }

    CursorFilter(CursorFilterClient client) {
        mClient = client;
    }

    @Override
    public CharSequence convertResultToString(Object resultValue) {
        return mClient.convertToString((Cursor) resultValue);
    }

    @Override
    protected Filter.FilterResults performFiltering(CharSequence constraint) {
        Cursor cursor = mClient.runQueryOnBackgroundThread(constraint);

        FilterResults results = new FilterResults();
        if (cursor != null) {
            results.count = cursor.getCount();
            results.values = cursor;
        } else {
            results.count = 0;
            results.values = null;
        }
        return results;
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
        Cursor oldCursor = mClient.getCursor();

        if (results.values != null && results.values != oldCursor) {
            mClient.changeCursor((Cursor) results.values);
        }
    }
}