将recyclerview与数据库一起使用

Question

目前没有可用的RecyclerView.Adapter的默认实现。

可能正式发布，谷歌将添加它。

由于CursorAdapter目前不支持RecyclerView，我们如何在数据库中使用RecyclerView？有什么建议 ？

Answer 1

如果您使用CursorLoader运行查询，并且您想要RecyclerView而不是ListView。

你可以尝试我的CursorRecyclerViewAdapter：CursorAdapter in RecyclerView

Answer 2

最后，我们为数据库/网络实现了RecyclerView.Adapter。

它用Android Architecture Components实现：

会议室数据库：SQLite数据库顶部的数据库层，负责处理您曾经使用SQLiteOpenHelper处理的普通任务。数据库持有者，用作底层SQLite数据库的访问点。 Room数据库使用DAO向SQLite数据库发出查询。

ViewModel：为UI提供数据。充当存储库和UI之间的通信中心。隐藏数据源自UI的位置。 ViewModel实例在Activity / Fragment娱乐中存活。

LiveData：可以观察的数据持有者类。始终保存/缓存最新版本的数据。数据发生变化时通知其观察者。 LiveData可识别生命周期。 UI组件只是观察相关数据，不会停止或恢复观察。 LiveData自动管理所有这些，因为它在观察时意识到相关的生命周期状态变化。

Answer 3

您可以使用SQLite数据库来存储详细信息。它很容易访问数据。你可以在github上查看我的代码。 https://github.com/thiru-wta/ToDo

     database = new Database(this);
    getSupportActionBar().setTitle("To Do List");
    etAddItems = (EditText) findViewById(R.id.etAddItem);
    btnAdd = (Button) findViewById(R.id.btnAdd);
    mRecyclerView = (RecyclerView) findViewById(R.id.listView);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    adapter = new RecyclerAdapter(this, listData);
    mRecyclerView.setAdapter(adapter);

    btnAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            event_name = etAddItems.getText().toString();
            String getname="";

              database.storeEventDetails(event_name);

                 getname = database.getEventDetails(event_name);


            if (getname.length() != 0) {
                listData.add(getname);
                etAddItems.setText("");

                adapter.notifyData(listData);
            }

数据库方法：

    public void storeEventDetails(String event_name, long timerStart) {
    SQLiteDatabase db1 = getWritableDatabase();
    db1.execSQL("insert into '"+event_details_tbl+"' values('" + event_name + "')");
    db1.close();
}

获取方法：

     public String getEventDetails(String event_name) {
    SQLiteDatabase db1 = getReadableDatabase();
    Cursor cur = db1.rawQuery("select * from '"+event_details_tbl+"' where     event_name ='" + event_name + "'", null);
    cur.moveToFirst();
    String evName = null;
    if (cur != null) {
        do {
            int eventName = cur.getColumnIndex("event_name");

            String ev_name = cur.getString(eventName);

            evName = ev_name;
        } while (cur.moveToNext());

    }
    cur.close();
    db1.close();
    return evName;

}     

Answer 4

您只需按照以下步骤操作：

• 在回收器view.adapter中，创建一个使用空值初始化的ArrayList或Iterator。
• 创建一个类似ex swapcursor的方法，例如swapdata(Arraylist<T> data)。在内部，您可以为数组列表，迭代器或系统可以使用bindview中的整数位置迭代的任何结构赋予新值。此方法的值在onloaderfinished()中传递。然后在assaznement notifydatachange()之后打电话;这些将要求RecyclerView使用ArrayList的新数据重绘所有列表。

在使用loadercalback的activity或fragment中，创建一个方法，将游标转换为arraylist或iterator，具体取决于在适配器中选择的数据结构。

这样，您始终可以使用loadercallbacks而不会阻塞主线程。

Answer 5

我的解决方案是在recyclerView.Adapter实现中保存CursorAdapter成员。然后传递创建新视图的所有处理并将其绑定到游标适配器，如下所示：

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);
    }
}

Answer 6

既然你的问题是“如何将RecyclerView与数据库一起使用”而你并不具体说明你是否想要使用RecyclerView的SQLite或其他任何东西，我会给你一个非常优化的解决方案。我将使用Realm作为数据库，让您显示RecyclerView中的所有数据。它还具有异步查询支持，无需使用Loaders或AsyncTask。

为什么境界？

步骤1

为Realm添加gradle依赖项，找到最新版本的依赖项here

第2步

创建你的模型类，例如，让我们说一些简单的东西，比如Data，它有2个字段，一个字符串显示在RecyclerView行内，一个时间戳将用作itemId，允许RecyclerView为项目设置动画。请注意，我在下面扩展了RealmObject，因为你的Data类将存储为一个表，所有属性都将存储为该表Data的列。我已将数据文本标记为我的主键，因为我不希望多次添加字符串。但是如果您更喜欢重复项，那么请将时间戳设为@PrimaryKey。您可以拥有一个没有主键的表，但如果您在创建后尝试更新该行，则会导致问题。 Realm不支持撰写此答案时的复合主键。

import io.realm.RealmObject;
import io.realm.annotations.PrimaryKey;

public class Data extends RealmObject {
@PrimaryKey
private String data;

//The time when this item was added to the database
private long timestamp;

public String getData() {
    return data;
}

public void setData(String data) {
    this.data = data;
}

public long getTimestamp() {
    return timestamp;
}

public void setTimestamp(long timestamp) {
    this.timestamp = timestamp;
}
}

第3步

创建一个单行应该如何出现在RecyclerView中的布局。我们的Adapter中单个行项目的布局如下

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

<TextView
    android:id="@+id/area"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@android:color/white"
    android:padding="16dp"
    android:text="Data"
    android:visibility="visible" />

</FrameLayout>

请注意，即使我有一个FrameLayout，我仍然保留了TextView作为root。我计划在这个布局中添加更多项目，因此现在变得灵活:)

对于那里的好奇人来说，这就是目前单个项目的外观。

第4步

创建你的RecyclerView.Adapter实现。在这种情况下，数据源对象是一个名为RealmResults的特殊对象，它基本上是一个LIVE ArrayList，换句话说，当你的表中添加或删除项目时，这个RealmResults对象会自动更新。

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import io.realm.Realm;
import io.realm.RealmResults;
import slidenerd.vivz.realmrecycler.R;
import slidenerd.vivz.realmrecycler.model.Data;

public class DataAdapter extends RecyclerView.Adapter<DataAdapter.DataHolder> {
private LayoutInflater mInflater;
private Realm mRealm;
private RealmResults<Data> mResults;

public DataAdapter(Context context, Realm realm, RealmResults<Data> results) {
    mRealm = realm;
    mInflater = LayoutInflater.from(context);
    setResults(results);
}

public Data getItem(int position) {
    return mResults.get(position);
}

@Override
public DataHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = mInflater.inflate(R.layout.row_data, parent, false);
    DataHolder dataHolder = new DataHolder(view);
    return dataHolder;
}

@Override
public void onBindViewHolder(DataHolder holder, int position) {
    Data data = mResults.get(position);
    holder.setData(data.getData());
}

public void setResults(RealmResults<Data> results) {
    mResults = results;
    notifyDataSetChanged();
}

@Override
public long getItemId(int position) {
    return mResults.get(position).getTimestamp();
}

@Override
public int getItemCount() {
    return mResults.size();
}

public void add(String text) {

    //Create a new object that contains the data we want to add
    Data data = new Data();
    data.setData(text);

    //Set the timestamp of creation of this object as the current time
    data.setTimestamp(System.currentTimeMillis());

    //Start a transaction
    mRealm.beginTransaction();

    //Copy or update the object if it already exists, update is possible only if your table has a primary key
    mRealm.copyToRealmOrUpdate(data);

    //Commit the transaction
    mRealm.commitTransaction();

    //Tell the Adapter to update what it shows.
    notifyDataSetChanged();
}

public void remove(int position) {

    //Start a transaction
    mRealm.beginTransaction();

    //Remove the item from the desired position
    mResults.remove(position);

    //Commit the transaction
    mRealm.commitTransaction();

    //Tell the Adapter to update what it shows
    notifyItemRemoved(position);
}

public static class DataHolder extends RecyclerView.ViewHolder {
    TextView area;

    public DataHolder(View itemView) {
        super(itemView);
        area = (TextView) itemView.findViewById(R.id.area);
    }

    public void setData(String text) {
        area.setText(text);
    }
}
}

请注意，我正在调用notifyItemRemoved，其中删除发生的位置但是我没有调用notifyItemInserted或notifyItemRangeChanged，因为没有直接的方法来知道项目被插入数据库的位置，因为Realm条目没有以有序的方式存储。每当从数据库添加，修改或删除新项目时，RealmResults对象都会自动更新，因此我们在添加和插入批量条目时调用notifyDataSetChanged。此时，您可能会关注不会触发的动画，因为您正在调用notifyDataSetChanged来代替notifyXXX方法。这正是为什么我有getItemId方法返回结果对象中每一行的时间戳。如果你调用notifyDataSetChanged然后覆盖setHasStableIds(true)以提供除了位置之外的其他东西，则使用getItemId以2个步骤实现动画。

第5步

让我们将RecyclerView添加到我们的Activity或Fragment。就我而言，我使用的是Activity。包含RecyclerView的布局文件非常简单，看起来像这样。

<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/recycler"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="@dimen/text_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />

我添加了一个app:layout_behavior，因为我的RecyclerView进入了CoordinatorLayout，为了简洁，我没有在这个答案中发布。

第6步

在代码中构造RecyclerView并提供它所需的数据。在onCreate中创建并初始化一个Realm对象并在onDestroy中关闭它，就像关闭一个SQLiteOpenHelper实例一样。最简单的是你在onCreate里面的Activity看起来像这样。 initUi方法是所有魔法发生的地方。我在onCreate中打开了一个Realm实例。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mRealm = Realm.getInstance(this);
    initUi();
}

private void initUi() {

    //Asynchronous query
    RealmResults<Data> mResults = mRealm.where(Data.class).findAllSortedAsync("data");

    //Tell me when the results are loaded so that I can tell my Adapter to update what it shows
    mResults.addChangeListener(new RealmChangeListener() {
        @Override
        public void onChange() {
            mAdapter.notifyDataSetChanged();
            Toast.makeText(ActivityMain.this, "onChange triggered", Toast.LENGTH_SHORT).show();
        }
    });
    mRecycler = (RecyclerView) findViewById(R.id.recycler);
    mRecycler.setLayoutManager(new LinearLayoutManager(this));
    mAdapter = new DataAdapter(this, mRealm, mResults);

    //Set the Adapter to use timestamp as the item id for each row from our database
    mAdapter.setHasStableIds(true);
    mRecycler.setAdapter(mAdapter);
}

请注意，在第一步中，我查询Realm以向我提供Data类中的所有对象，这些对象按其异步方式称为data的变量名进行排序。这给了我一个RealmResults对象，主线程上有0个项目，我在Adapter上设置。我添加了一个RealmChangeListener，当数据从后台线程完成加载时通知我用notifyDataSetChanged调用Adapter。我还将setHasStableIds称为true，让RecyclerView.Adapter实现跟踪添加，删除或修改的项目。我的onDestroy的Activity关闭了Realm实例

@Override
protected void onDestroy() {
    super.onDestroy();
    mRealm.close();
}

这个方法initUi可以在你的onCreate的Activity或onCreateView的onViewCreated或Fragment内部调用。请注意以下事项。

第7步

BAM！你的RecyclerView数据库中的数据是异常加载的，没有CursorLoader，CursorAdapter，带有动画的SQLiteOpenHelper。此处显示的GIF图像有点滞后，但是当您添加项目或删除它们时会发生动画。

Answer 7

您可以自己实现所有必需的方法。我最近通过从CursorAdapter复制粘贴代码来实现自己的实现。

public class MyAdapter extends RecyclerView.Adapter<ViewHolder> {

        protected boolean mDataValid;
        protected boolean mAutoRequery;
        protected Cursor mCursor;
        protected Context mContext;
        protected int mRowIDColumn;
        protected ChangeObserver mChangeObserver;
        protected DataSetObserver mDataSetObserver;
        protected FilterQueryProvider mFilterQueryProvider;
        public static final int FLAG_AUTO_REQUERY = 0x01;
        public static final int FLAG_REGISTER_CONTENT_OBSERVER = 0x02;

        public Cursor getCursor() {
            return mCursor;
        }

        //Recommended
        public MyAdapter(Context context, Cursor c, int flags) {
            init(context, c, flags);
        }

        public MyAdapter(Context context, Cursor c) {
            init(context, c, FLAG_AUTO_REQUERY);
        }

        public MyAdapter(Context context, Cursor c, boolean autoRequery) {
            init(context, c, autoRequery ? FLAG_AUTO_REQUERY : FLAG_REGISTER_CONTENT_OBSERVER);
        }

        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);
            }
        }

        // Create new views (invoked by the layout manager)
        @Override
        public ViewHolder onCreateViewHolder(final ViewGroup parent,
                                             int viewType) {
            // create a new view
            final View view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.list_item, parent, false);
            // set the view's size, margins, paddings and layout parameters

            ViewHolder vh = new ViewHolder(view, mCursor, new ViewHolder.IMyViewHolderClicks() {

                @SuppressLint("NewApi")
                @Override
                public void onClick(Cursor cursor) {
                    Log.e("Item :", cursor.getString(cursor.getColumnIndex(MyDatabaseHelper.MW_NAAM)));
                    Intent intent = new Intent(TasksListFragment.this.getActivity(), DetailActivity.class);
                    intent.putExtra(DetailActivity.EXTRA_PARAM_ID, cursor.getLong(cursor.getColumnIndex(MyDatabaseHelper.MW_ID)));

                    ActivityOptions activityOptions = ActivityOptions.makeSceneTransitionAnimation(
                            TasksListFragment.this.getActivity(),

                            // Now we provide a list of Pair items which contain the view we can transitioning
                            // from, and the name of the view it is transitioning to, in the launched activity
                            new Pair<View, String>(
                                    view.findViewById(R.id.imageview_item),
                                    DetailActivity.VIEW_NAME_HEADER_IMAGE),
                            new Pair<View, String>(
                                    view.findViewById(R.id.textview_name),
                                    DetailActivity.VIEW_NAME_HEADER_TITLE)
                    );

                    // Now we can start the Activity, providing the activity options as a bundle
                    startActivity(intent, activityOptions.toBundle());
                    // END_INCLUDE(start_activity)
                }
            });
            return vh;
        }

        // Replace the contents of a view (invoked by the layout manager)
        @SuppressLint("NewApi")
        @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            // - get element from your dataset at this position
            // - replace the contents of the view with that element
            final Cursor cursor = getItem(position);

            holder.mTextView.setText(cursor.getString(cursor.getColumnIndex(MyDatabaseHelper.MW_NAAM)));
            holder.mImageView.setTransitionName("grid:image:" + cursor.getLong(cursor.getColumnIndex(MyDatabaseHelper.MW_ID)));
            holder.mTextView.setTransitionName("grid:name:" + cursor.getLong(cursor.getColumnIndex(MyDatabaseHelper.MW_ID)));
        }

        //@Override
        // public View getView(int position, View view, ViewGroup viewGroup) {
        //     return view;
        // }

        // Return the size of your dataset (invoked by the layout manager)
        @Override
        public int getItemCount() {
            return getCount();
        }

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

        public Cursor getItem(int position) {
            if (mDataValid && mCursor != null) {
                mCursor.moveToPosition(position);
                return mCursor;
            } else {
                return null;
            }
        }

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

        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
                notifyDataSetInvalidated();
            }
            return oldCursor;
        }

        public void changeCursor(Cursor cursor) {
            Cursor old = swapCursor(cursor);
            if (old != null) {
                old.close();
            }
        }

        public CharSequence convertToString(Cursor cursor) {
            return cursor == null ? "" : cursor.toString();
        }

        public Cursor runQueryOnBackgroundThread(CharSequence constraint) {
            if (mFilterQueryProvider != null) {
                return mFilterQueryProvider.runQuery(constraint);
            }
            return mCursor;
        }


        public FilterQueryProvider getFilterQueryProvider() {
            return mFilterQueryProvider;
        }

        public void setFilterQueryProvider(FilterQueryProvider filterQueryProvider) {
            mFilterQueryProvider = filterQueryProvider;
        }

        protected void onContentChanged() {
            if (mAutoRequery && mCursor != null && !mCursor.isClosed()) {
                if (false) Log.v("Cursor", "Auto requerying " + mCursor + " due to update");
                mDataValid = mCursor.requery();
            }
        }

        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;
                notifyDataSetInvalidated();
            }
        }


        private final DataSetObservable mDataSetObservable = new DataSetObservable();

        public void registerDataSetObserver(DataSetObserver observer) {
            mDataSetObservable.registerObserver(observer);
        }

        public void unregisterDataSetObserver(DataSetObserver observer) {
            mDataSetObservable.unregisterObserver(observer);
        }

        public void notifyDataSetInvalidated() {
            mDataSetObservable.notifyInvalidated();
        }
    }

Answer 8

我使用RecyclerViewCursorAdapter作为后端制作了SortedList，扩展了RecyclerView.Adapter

可以与SQLiteCursor和Loaders一起使用

Answer 9

只是另一个答案，因为我不喜欢被接受的那个（imo没有直观的用法）。

以下是我自己的实现，它与SimpleCursorAdapter非常相似（并且部分受到启发）：

public class RecyclerViewSimpleCursorAdapter extends RecyclerView.Adapter {
    private int mLayout;
    private Cursor mCursor;
    private String[] mFrom;
    private int[] mTo;

    private boolean mAutoRequery;
    private ContentObserver mContentObserver;

    /**
     * Standard constructor.
     *
     * @param layout resource identifier of a layout file that defines the views for this list item. The layout file should include at least those named views defined in "to"
     * @param c      The database cursor. Can be null if the cursor is not available yet.
     * @param from   A list of column names representing the data to bind to the UI. Can be null if the cursor is not available yet.
     * @param to     The views that should display column in the "from" parameter. These should all be TextViews and ImageViews. The first N views in this list are given the values of the first N columns in the from parameter. Can be null if the cursor is not available yet.
     */
    public RecyclerViewSimpleCursorAdapter(int layout, Cursor c, String[] from, int[] to, boolean autoRequery) {
        mLayout = layout;
        mCursor = c;
        mFrom = from;
        mTo = to;
        mAutoRequery = autoRequery;

        if (mAutoRequery) {
            initializeContentObserver();
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new RecyclerView.ViewHolder(
                LayoutInflater.from(parent.getContext())
                        .inflate(mLayout, parent, false)
        ) {
        };
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        mCursor.moveToPosition(position);

        if (mFrom == null || mTo == null)
            return;

        for (int i = 0; i < mFrom.length && i < mTo.length; i++) {
            String from = mFrom[i];
            int columnIndex = mCursor.getColumnIndex(from);
            String value = mCursor.getString(columnIndex);
            View view = holder.itemView.findViewById(mTo[i]);

            if (view instanceof TextView) {
                ((TextView) view).setText(value);
            } else if (view instanceof ImageView) {
                try {
                    ((ImageView) view).setImageResource(Integer.parseInt(value));
                } catch (NumberFormatException nfe) {
                    ((ImageView) view).setImageURI(Uri.parse(value));
                }
            } else {
                throw new IllegalStateException(view.getClass().getName() + " is not a view that can be bound by this RecyclerViewSimpleCursorAdapter");
            }
        }
    }

    @Override
    public int getItemCount() {
        return mCursor  != null ? mCursor.getCount() : 0;
    }

    private void initializeContentObserver() {
        mContentObserver = new ContentObserver(new Handler()) {
            @Override
            public boolean deliverSelfNotifications() {
                return true;
            }

            @Override
            public void onChange(boolean selfChange) {
                notifyDataSetChanged();
            }
        };
        mCursor.registerContentObserver(mContentObserver);
    }

    /**
     * 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 oldCursor = mCursor;
        if (mAutoRequery) {
            if (mCursor != null) {
                mCursor.unregisterContentObserver(mContentObserver);
            }

            mContentObserver = new ContentObserver(new Handler()) {
                @Override
                public boolean deliverSelfNotifications() {
                    return true;
                }

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

            mCursor = cursor;
            if (mCursor != null) {
                mCursor.registerContentObserver(mContentObserver);
            }
        }

        notifyDataSetChanged();

        if (oldCursor != null && oldCursor != mCursor) {
            oldCursor.close();
        }
    }

    /**
     * Change the cursor and change the column-to-view mappings at the same time.
     *
     * @param cursor The database cursor. Can be null if the cursor is not available yet.
     * @param from A list of column names representing the data to bind to the UI. Can be null if the cursor is not available yet.
     * @param to The views that should display column in the "from" parameter. These should all be TextViews or ImageViews. The first N views in this list are given the values of the first N columns in the from parameter. Can be null if the cursor is not available yet.
     */
    public void changeCursorAndColumns(Cursor cursor, String[] from, int[] to) {
        mFrom = from;
        mTo = to;
        changeCursor(cursor);
    }

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

您可以修改它以用于其他特定用途，但是使用光标它就像SimpleCursorAdapter一样，只有RecyclerView。

Answer 10

从数据库中检索数据并存储在列表中后，可能应该是这样的：

    dbHelper = new BooksDbAdapter(this);
    dbHelper.open();
    //Clean all data
    dbHelper.deleteAllZist();
    //Add some data
    dbHelper.insertSomeRecords();
    List<String> mylist = dbHelper.getArrayColumn(3);

将数据添加到recyclerview

list = new ArrayList<DataObject>();
 Integer i=0;
    for (String lst : mylist) {
        list.add(i++, new DataObject(lst,
                "The RecyclerView widget is a more advanced and flexible 
               version of ListView."));
    }

    recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
    recyclerView.setHasFixedSize(true);
    myRecAdapter = new RecyclerviewAdapter(list, Zist1ChapterActivity.this);

Answer 11

下面是我对recyclerview的cursoradapter的实现。它支持OnItemClickListener，OnLongItemClickListener，OnfooterClickListener，Sections和footer。不支持，Header，onHeaderClickListner，快速滚动条，粘贴标题或粘性部分。

只需扩展此适配器并创建自己的适配器。覆盖提供的方法。并从OnCursorLoadFinished方法传递光标。如果已经创建了适配器，那么swapCursor（）

package com.tracker.paisa;

import android.database.Cursor;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.util.SparseBooleanArray;
import android.view.ViewGroup;
import java.util.ArrayList;
import java.util.List;


/**
 * @author Rahul Upadhyay (https://github.com/devDroidRaul)
 * Supports footer
 * Onitemclicklistener, OnItemLongClickListener, OnFooterClickListener
 * Supports Sections.
 *
 * Does Not support,Header, OnHeaderClickListener, FastScroller, StickySection (this can b done with item decor)
 * Pull requests are welcome for improvements.
 *
 * Override this to give logic to place subheaders between items.
 * public abstract boolean onPlaceSubheaderBetweenItems(int position);
 *
 * create seperate viewHolders for item, subheaders and footer. and return required views.
 *
 * @Override below methods for individual item type.
 * public abstract VH onCreateItemViewHolder(ViewGroup parent, int viewType);
 * public abstract SH onCreateSubheaderViewHolder(ViewGroup parent, int viewType);
 * public abstract FH onCreateFooterViewHolder(ViewGroup parent, int viewType);
 *
 * Bind your views with data here.
 * @Override below methods to bind data to individual item types.
 * public abstract void onBindSubHeaderViewHolder(SH holder, Cursor cursor);
 * public abstract void onBindItemViewHolder(VH holder, Cursor cursor);
 * public abstract void onBindFooterViewHolder(FH holder, int itemPosition);
 *
 * Item type -1,-2,-3 are reserved, kindly do not pass them in getItemViewType.
 */

public abstract class RecyclerViewCursorAdapter<SH extends RecyclerView.ViewHolder, VH extends RecyclerView.ViewHolder, FH extends RecyclerView.ViewHolder>
        extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    public static final String TAG = RecyclerViewCursorAdapter.class.getSimpleName();

    private static final int TYPE_SECTION_HEADER = -1;

    private static final int TYPE_MAIN_HEADER = -2;
    private static final int TYPE_FOOTER = -3;

   // private int headerLayout=0,viewLayout=0;
    boolean createHeader;

    private List<Integer> subheaderPositions = new ArrayList<>();

    private Cursor mCursor;
    private boolean mDataValid,footerRequired=false;
    private int mRowIDColumn;
    private SparseBooleanArray mSelectedItemsIds;



   // public RecyclerViewCursorAdapter() { }

    //constructor
    public RecyclerViewCursorAdapter(Cursor c,boolean footerRequired) {
        setHasStableIds(true);
        swapCursor(c);
        this.footerRequired = footerRequired;

        this.mSelectedItemsIds = new SparseBooleanArray();
    }



    // interface for listning click on recycler view;
    public interface OnItemClickedListener{
        void OnItemClick(int id, Object data);

        void onItemLongClick(int id);
    }

    OnItemClickedListener onItemClickedListener;

    public void setOnItemClickedListener(OnItemClickedListener onItemClickedListener) {
        this.onItemClickedListener = onItemClickedListener;
    }

    public interface OnFooterClickedListener{
        void onFooterClick(Object data);
    }

    OnFooterClickedListener onFooterClickedListener;
    public void setOnFooterClickedListener( OnFooterClickedListener onFooterClickedListener){
        this.onFooterClickedListener = onFooterClickedListener;
    }

    public interface OnHeaderClickedListener{
        void onHeaderClick(Object data);
    }

    OnHeaderClickedListener onHeaderClickedListener;
    public void setOnHeaderClickedListener( OnHeaderClickedListener onHeaderClickedListener){
        this.onHeaderClickedListener = onHeaderClickedListener;
    }

    private void initSubheaderPositions() {
        subheaderPositions.clear();

        if(getItemSize() != 0) {
            //TODO:Handle This please.
            //subheaderPositions.add(0);
        } else {
            return;
        }

        for(int i = 1; i < getItemSize(); i++) {
            if(onPlaceSubheaderBetweenItems(i - 1)) {
                subheaderPositions.add(i + subheaderPositions.size());
            }
        }
    }

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {

            initSubheaderPositions();



    }

    /**
     * Called when adapter needs to know whether to place subheader between two neighboring
     * items.
     *
     * @return true if you want to place subheader between two neighboring
     * items.
     */
    public abstract boolean onPlaceSubheaderBetweenItems(int position);

    public abstract VH onCreateItemViewHolder(ViewGroup parent, int viewType);

    public abstract SH onCreateSubheaderViewHolder(ViewGroup parent, int viewType);

    public abstract FH onCreateFooterViewHolder(ViewGroup parent, int viewType);

    public abstract void onBindSubHeaderViewHolder(SH holder, Cursor cursor);

    public abstract void onBindItemViewHolder(VH holder, Cursor cursor);

    public abstract void onBindFooterViewHolder(FH holder, int itemPosition);






    public abstract int getItemSize();

    /**
     * Return the view type of the item at position for the purposes
     * of view recycling.
     * Don't return -1. It's reserved for subheader view type.
     */
    public int getViewType(int position) {
        return 0;
    }

    @Override
    public final int getItemViewType(int position) {

        if(isSubheaderOnPosition(position)) {
            return TYPE_SECTION_HEADER;
        } if(footerRequired && getCursor().getPosition()==(getCursor().getCount()-1)){
            return TYPE_FOOTER;
        }else {
            return getViewType(position);
        }
    }

    public boolean isFooterAdded(){
        return footerRequired;
    }
    @Override
    public final RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        Log.d("RVCA-OCVH","create viewholder");
        if(viewType == TYPE_SECTION_HEADER) {
            return onCreateSubheaderViewHolder(parent, viewType);
        } if(footerRequired&&viewType == TYPE_FOOTER){
            return onCreateFooterViewHolder(parent, viewType);
        }else {
            return onCreateItemViewHolder(parent, viewType);
        }
    }

    @SuppressWarnings("unchecked")
    @Override
    public final void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        Log.d("RVCA-OBVH","bind viewholder");
        Log.d("RVCA-OBVH","subheader position:"+isSubheaderOnPosition(position));
        if(isSubheaderOnPosition(position)) {
            if (!mDataValid) {
                throw new IllegalStateException("Cannot bind viewholder when cursor is in invalid state.");
            }
            if (!mCursor.moveToPosition(getItemPositionForViewHolder(position))) {
                throw new IllegalStateException("Could not move cursor to position " + getItemPositionForViewHolder(position) + " when trying to bind viewholder");
            }

            onBindSubHeaderViewHolder((SH)holder, mCursor);
        }if(footerRequired && position==getItemCount()-1){
            Log.d("RVCA-OBVH","bind footerHolder");
            onBindFooterViewHolder((FH) holder,position);

        } else {
            if (!mDataValid) {
                throw new IllegalStateException("Cannot bind viewholder when cursor is in invalid state.");
            }
            if (!mCursor.moveToPosition(getItemPositionForViewHolder(position))) {
                throw new IllegalStateException("Could not move cursor to position " + getItemPositionForViewHolder(position) + " when trying to bind viewholder");
            }
            // if(!mCursor.isAfterLast()) {
            //   mCursor.moveToPosition(position);
            onBindItemViewHolder((VH)holder, mCursor);

        }
    }

    @Override
    public final int getItemCount() {
        return getItemSize() + subheaderPositions.size()+(footerRequired?1:0);
    }

    public void notifyDataChanged() {
        initSubheaderPositions();
        notifyDataSetChanged();
    }

    public void notifyItemInsertedAtPosition(int itemPosition) {
        if (itemPosition == 0) {
            if (getItemCount() == 1 || onPlaceSubheaderBetweenItems(itemPosition)) {
                subheaderPositions.add(0, 0);
                increaseSubheaderPositions(1, 2);
                notifyItemRangeInserted(0, 2);
            } else {
                increaseSubheaderPositions(1, 1);
                notifyItemInserted(1);
            }
        } else if (itemPosition == getItemSize() - 1) {
            if (onPlaceSubheaderBetweenItems(itemPosition - 1)) {
                subheaderPositions.add(getItemCount() - 1);
                notifyItemRangeInserted(getItemCount() - 1, 2);
            } else {
                notifyItemInserted(getItemPositionInRecyclerView(itemPosition));
            }
        } else {
            if (onPlaceSubheaderBetweenItems(itemPosition - 1) && onPlaceSubheaderBetweenItems(itemPosition)) {
                final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition - 1);
                final int countOfSubheadersBeforePosition = getCountOfSubheadersBeforePosition(itemPositionInRv);
                subheaderPositions.add(countOfSubheadersBeforePosition, itemPositionInRv + 1);
                increaseSubheaderPositions(countOfSubheadersBeforePosition + 1, 2);
                notifyItemRangeInserted(itemPositionInRv + 1, 2);
            } else if (onPlaceSubheaderBetweenItems(itemPosition)){
                final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition - 1);
                increaseSubheaderPositions(getCountOfSubheadersBeforePosition(itemPositionInRv), 1);
                notifyItemInserted(itemPositionInRv + 1);
            } else if (onPlaceSubheaderBetweenItems(itemPosition - 1)) {
                final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
                increaseSubheaderPositions(getCountOfSubheadersBeforePosition(itemPositionInRv), 1);
                notifyItemInserted(itemPositionInRv);
            } else {
                final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
                increaseSubheaderPositions(getCountOfSubheadersBeforePosition(itemPositionInRv), 1);
                notifyItemInserted(itemPositionInRv);
            }
        }
    }

    public void notifyItemChangedAtPosition(int itemPosition) {
        final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);
        notifyItemChanged(itemPositionInRv);
    }

    public void notifyItemRemovedAtPosition(int itemPosition) {

        final int itemPositionInRv = getItemPositionInRecyclerView(itemPosition);

        for (int i = 1; i < subheaderPositions.size(); i++) {
            final int subheaderPosition = subheaderPositions.get(i);
            if (subheaderPosition > itemPositionInRv) {
                final int previousSubheaderPosition = subheaderPositions.get(i - 1);
                if (subheaderPosition - previousSubheaderPosition == 2) {
                    subheaderPositions.remove(subheaderPositions.indexOf(previousSubheaderPosition));
                    decreaseSubheaderPositions(subheaderPositions.indexOf(subheaderPosition), 2);
                    notifyItemRangeRemoved(itemPositionInRv - 1, 2);
                } else {
                    decreaseSubheaderPositions(subheaderPositions.indexOf(subheaderPosition), 1);
                    notifyItemRemoved(itemPositionInRv);
                }
                return;
            }
        }

        final int lastSubheaderPosition = subheaderPositions.get(subheaderPositions.size() - 1);
        if (itemPositionInRv - lastSubheaderPosition == 1 && getItemCount() == itemPosition + subheaderPositions.size()) {
            subheaderPositions.remove(subheaderPositions.size() - 1);
            notifyItemRangeRemoved(itemPositionInRv - 1, 2);
        } else {
            notifyItemRemoved(itemPositionInRv);
        }
    }

    public void setGridLayoutManager(final GridLayoutManager gridLayoutManager) {
        gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
            @Override
            public int getSpanSize(int position) {
                if(subheaderPositions.contains(position)) {
                    return gridLayoutManager.getSpanCount();
                } else {
                    return 1;
                }
            }
        });
    }

    public boolean isSubheaderOnPosition(int position) {
        return subheaderPositions.contains(position);
    }

    public int getCountOfSubheadersBeforePosition(int position) {
        int count = 0;
        for(int subheaderPosition : subheaderPositions) {
            if(subheaderPosition < position) {
                count++;
            }
        }
        return count;
    }

    public int getItemPositionInRecyclerView(int position) {
        int countOfItems = 0;
        for (int i = 1; i < subheaderPositions.size(); i++) {
            final int previousSubheaderPosition = subheaderPositions.get(i - 1);
            final int nextSubheaderPosition = subheaderPositions.get(i);
            countOfItems += nextSubheaderPosition - previousSubheaderPosition - 1;
            if (countOfItems > position) {
                return position + i;
            }
        }
        return position + subheaderPositions.size();
    }

    public int getItemPositionForViewHolder(int viewHolderPosition) {
        return viewHolderPosition - getCountOfSubheadersBeforePosition(viewHolderPosition);
    }

    private void decreaseSubheaderPositions(int startSubheaderPosition, int decreaseNum) {
        for (int i = startSubheaderPosition; i < subheaderPositions.size(); i++) {
            final int subheaderPosition = subheaderPositions.get(i);
            subheaderPositions.set(i, subheaderPosition - decreaseNum);
        }
    }

    private void increaseSubheaderPositions(int startSubheaderPosition, int increaseNum) {
        for (int i = startSubheaderPosition; i < subheaderPositions.size(); i++) {
            final int subheaderPosition = subheaderPositions.get(i);
            subheaderPositions.set(i, subheaderPosition + increaseNum);
        }
    }

    private List<Integer> getSubheaderPositions() {
        return subheaderPositions;
    }

    public int getSubheaderCount() {
        return subheaderPositions.size();
    }

    public void swapCursor(Cursor newCursor) {
        Log.d("RVCA-SC","swap cursor");
        if (newCursor == mCursor) {
            Log.d("RVCA-SC","same cursor doing nothing");
            return;
        }

        if (newCursor != null) {
            Log.d("RVCA-SC","swap cursor not null");
            mCursor = newCursor;
            mRowIDColumn = mCursor.getColumnIndexOrThrow("_id");
            mDataValid = true;

            // notify the observers about the new cursor
            notifyDataChanged();
        } else {
            Log.d("RVCA-SC","swap cursor null");
            notifyItemRangeRemoved(0, getItemCount());
            mCursor = null;
            mRowIDColumn = -1;
            mDataValid = false;
        }
    }

    public Cursor getCursor(){
        return mCursor ;
    }

    @Override
    public long getItemId(int position) {
        if (isSubheaderOnPosition(position))
            return position;
        else {
            int cursorPosition = getItemPositionForViewHolder(position);
            Cursor cursor = getCursor();
            if (hasOpenCursor() && cursor.moveToPosition(cursorPosition)) {
                return cursor.getLong(cursor.getColumnIndex("_id"));
            }
            return NO_CURSOR_POSITION;
        }
    }
    public static final int NO_CURSOR_POSITION = -99;

    protected boolean hasOpenCursor() {
        Cursor cursor = getCursor();
        if (cursor == null || cursor.isClosed()) {
            swapCursor(null);
            return false;
        }
        return true;
    }

    //Methods to do Selection

    public void toggleSelection(int position) {
        selectView(position, !mSelectedItemsIds.get(position));
    }


    //Remove selected selections
    public void removeSelection() {
        mSelectedItemsIds = new SparseBooleanArray();
        notifyDataSetChanged();
    }


    //Put or delete selected position into SparseBooleanArray
    public void selectView(int position, boolean value) {
        if (value)
            mSelectedItemsIds.put(position, value);
        else
            mSelectedItemsIds.delete(position);

        // notifyItemChangedAtPosition(position);
        notifyDataSetChanged();
    }

    //Get total selected count
    public int getSelectedCount() {
        return mSelectedItemsIds.size();
    }

    //Return all selected ids
    public SparseBooleanArray getSelectedIds() {
        return mSelectedItemsIds;
    }

    public void setSelectedItemIds(SparseBooleanArray selectedItemIds){
        this.mSelectedItemsIds=selectedItemIds;
    }


}

Answer 12

最简单的实现是在适配器中使用游标对象并将游标传递给视图构造函数，以便修改视图并更改onBindViewholder中的光标位置。

如果你使用游标Loader调用onLoadfinished()中的setCursor方法并在onLoadReset()中传递null

public class PetCursorRecyclerViewAdapter extends RecyclerView.Adapter<PetCursorRecyclerViewAdapter.ViewHolder> {
Cursor cursor = null;
Context context;

public PetCursorRecyclerViewAdapter(Context context) {
    this.context = context;

}

public void setCursor(Cursor cursor) {
    this.cursor = cursor;
    notifyDataSetChanged();
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(context).inflate(R.layout.catalog_item, parent, false);
    return new ViewHolder(v);
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    this.cursor.moveToPosition(position);
    holder.bindModel(this.cursor);
}

/*   getItemCount() returns the count of videos from the Cursor, or 0 if the
   Cursor is null (mimicking the behavior of CursorAdapter, which also treats
   a null Cursor as merely being one that has no rows)*/
@Override
public int getItemCount() {
    if (cursor == null) {
        return 0;
    } else {
        return cursor.getCount();
    }
}

public static class ViewHolder extends RecyclerView.ViewHolder {
    private TextView name_tv, breed_tv;

    public ViewHolder(View itemView) {
        super(itemView);
        name_tv = (TextView) itemView.findViewById(R.id.name_tv);
        breed_tv = (TextView) itemView.findViewById(R.id.breed_tv);
    }

    public void bindModel(Cursor cursor) {
        int name_index = cursor.getColumnIndexOrThrow(PetsContract.PetEntry.COLUMN_PET_NAME);
        int breed_index = cursor.getColumnIndexOrThrow(PetsContract.PetEntry.COLUMN_PET_BREED);
        name_tv.setText(cursor.getString(name_index));
        String breed = cursor.getString(breed_index);
        if (TextUtils.isEmpty(breed)) {
            breed = "Unknown Breed";
        }
        breed_tv.setText(breed);
    }
}    

}