android - 将 recyclerview 与数据库一起使用

Question

目前没有 RecyclerView.Adapter 的默认实现可用。

可能随着正式发布，谷歌会添加它。

由于目前不支持CursorAdapterwith RecyclerView，我们如何将 aRecyclerView与数据库一起使用？有什么建议么 ？

Answer 1

如果您正在使用 a 运行查询，CursorLoader并且您想要RecyclerView而不是ListView.

你可以试试我的CursorRecyclerViewAdapter：CursorAdapter in RecyclerView

Answer 2

我的解决方案是在我的 recyclerView.Adapter 实现中保留一个 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 3

由于您的问题是“如何RecyclerView与数据库一起使用”，并且您并没有具体说明您是否需要 SQLite 或其他任何东西，所以RecyclerView我将为您提供一个高度优化的解决方案。我将使用Realm作为数据库，让您在RecyclerView. 它也具有异步查询支持，而无需使用Loadersor AsyncTask。

为什么是境界？

步骤1

为 Realm 添加 gradle 依赖，最新版本的依赖在这里

第2步

例如，创建您的模型类，让我们说一些简单的事情，比如Data它有 2 个字段、一个要在行内显示的字符串RecyclerView和一个时间戳，该时间戳将用作 itemId 以允许RecyclerView为项目设置动画。请注意，我在下面进行了扩展RealmObject，因此您的Data类将存储为表，并且您的所有属性都将存储为该表的列Data。在我的情况下，我已将数据文本标记为主键，因为我不希望多次添加字符串。但如果您更喜欢重复，则将时间戳设为@PrimaryKey。您可以拥有一个没有主键的表，但如果您在创建该行后尝试更新该行，则会导致问题。在撰写此答案时，Realm 不支持复合主键。

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

为单行应如何出现在RecyclerView. 我们内部单行项的布局Adapter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，FrameLayout即使我有一个TextView内部，我也将 a 保留为 root。我计划在此布局中添加更多项目，因此现在使其灵活:)

对于好奇的人来说，这就是当前单个项目的外观。

第4步

创建你的RecyclerView.Adapter实现。在这种情况下，数据源对象是一个称为RealmResultsLIVE的特殊对象ArrayList，换句话说，当从表中添加或删除项目时，此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删除发生的位置，但我没有调用notifyItemInserted，或者notifyItemRangeChanged因为没有直接的方法知道项目被插入到数据库中的哪个位置，因为 Realm 条目没有以有序的方式存储。RealmResults每当从数据库中添加、修改或删除新项目时，对象都会自动更新，因此我们在notifyDataSetChanged添加和插入批量条目时调用。此时，您可能担心动画不会被触发，因为您正在调用notifyDataSetChanged代替notifyXXX方法。这正是我让该getItemId方法从结果对象返回每一行的时间戳的原因。notifyDataSetChanged如果您调用setHasStableIds(true)然后覆盖，则动画分两步实现getItemId提供除了职位以外的东西。

第 5 步

让我们添加RecyclerView到我们的ActivityorFragment中。就我而言，我使用的是Activity. 包含 的布局文件RecyclerView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" />

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

第 6 步

构造RecyclerViewin 代码并提供它需要的数据。在里面创建和初始化一个 Realm 对象，然后在里面onCreate关闭它，onDestroy就像关闭一个SQLiteOpenHelper实例一样。在最简单的情况下，您的onCreate内部Activity将看起来像这样。该initUi方法是所有魔术发生的地方。我在里面打开了一个 Realm 实例onCreate。

@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，这些对象按它们的变量名排序，称为数据，以异步方式。这给了我一个RealmResults在主线程上有 0 个项目的对象，我在Adapter. 我添加了一个RealmChangeListener当数据从我调用的后台线程完成加载时得到通知notifyDataSetChanged的Adapter. 我还调用setHasStableIds了 true 以让RecyclerView.Adapter实现跟踪添加、删除或修改的项目。onDestroyfor myActivity关闭 Realm实例

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

此方法initUi可以在onCreate您的Activity或onCreateView或onViewCreated您的Fragment. 请注意以下事项。

第 7 步

砰！没有, ,动画的RecyclerView异步加载中有来自数据库的数据。此处显示的 GIF 图像有点滞后，但是当您添加或删除项目时会出现动画。 CursorLoaderCursorAdapterSQLiteOpenHelper

Answer 4

您可以自己实现所有必需的方法。我最近通过从 CursorAdapter 复制粘贴代码进行了自己的实现。

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 5

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

可以与SQLiteCursor和Loaders一起使用

Answer 6

只是另一个答案，因为我不喜欢接受的答案（imo没有直观的用法）。

以下是我自己的实现，与（部分受启发）非常相似SimpleCursorAdapter：

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;
    }
}

您可以针对其他特定用途对其进行修改，但使用游标时它的工作方式与以前SimpleCursorAdapter一样，仅使用RecyclerView.

Answer 7

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);

添加数据到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 8

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viewholder构造函数以修改视图并更改onBindViewholder中的游标位置。

如果您使用游标加载器，请调用 setCursor 方法onLoadfinished()并传入 nullonLoadReset()

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);
    }
}    

}

Answer 9

最后，我们为数据库/网络实现了 RecyclerView.Adapter。

它通过 Android架构组件实现：

Room 数据库： SQLite 数据库之上的数据库层，负责处理您过去使用SQLiteOpenHelper. 用作底层 SQLite 数据库访问点的数据库持有者。Room 数据库使用 DAO 向 SQLite 数据库发出查询。

ViewModel：向 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 重新创建后仍然存在。

LiveData：可以观察到的数据持有者类。始终保存/缓存最新版本的数据。当数据发生变化时通知其观察者。LiveData 具有生命周期意识。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，因为它在观察时知道相关的生命周期状态变化。

Answer 10

下面是我为 recyclerview 实现的 cursoradapter。它支持 OnItemClickListener、OnLongItemClickListener、OnfooterClickListener、Sections 和 footer。不支持, Header, onHeaderClickListner, fast scroller, sticky header 或 sticky section。

只需扩展此适配器并创建您自己的适配器。覆盖提供的方法。并从 OnCursorLoadFinished 方法传递光标。如果适配器已经创建，则 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 11

您可以使用 SQLite 数据库来存储详细信息。访问数据很容易。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 12

您只需按照以下步骤操作：

• 在 recyclerview.adapter中，创建一个初始化为空值的 ArrayList 或 Iterator。
• 创建一个类似 ex swapcursor 的方法，例如swapdata(Arraylist<T> data). 在内部，您为数组列表、迭代器或系统可以使用绑定视图中的整数位置迭代的任何结构提供一个新值。此方法的值在onloaderfinished(). 然后在分配后立即调用notifydatachange()；这些将要求RecyclerView使用 ArrayList 的新数据重绘所有列表。

在您使用 loadercalback 的活动或片段中，创建一个将光标转换为数组列表或迭代器的方法，具体取决于适配器中选择的数据结构。

这样，您始终可以使用 loadercalback 而不会阻塞主线程。