Drag and drop items in RecyclerView with GridLayoutManager

There is actually a better way to achieve this. You can use some of the RecyclerView's "companion" classes:

ItemTouchHelper, which is

a utility class to add swipe to dismiss and drag & drop support to RecyclerView.

and its ItemTouchHelper.Callback, which is

the contract between ItemTouchHelper and your application

// Create an `ItemTouchHelper` and attach it to the `RecyclerView`
ItemTouchHelper ith = new ItemTouchHelper(_ithCallback);
ith.attachToRecyclerView(rv);

// Extend the Callback class
ItemTouchHelper.Callback _ithCallback = new ItemTouchHelper.Callback() {
    //and in your imlpementaion of
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        // get the viewHolder's and target's positions in your adapter data, swap them
        Collections.swap(/*RecyclerView.Adapter's data collection*/, viewHolder.getAdapterPosition(), target.getAdapterPosition());
        // and notify the adapter that its dataset has changed
        _adapter.notifyItemMoved(viewHolder.getAdapterPosition(), target.getAdapterPosition());
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        //TODO    
    }

    //defines the enabled move directions in each state (idle, swiping, dragging). 
    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        return makeFlag(ItemTouchHelper.ACTION_STATE_DRAG,
                ItemTouchHelper.DOWN | ItemTouchHelper.UP | ItemTouchHelper.START | ItemTouchHelper.END);
    }
};

For more details check their documentation.

This is my solution with database reordering:

    ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP | ItemTouchHelper.DOWN, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
        @Override
        public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
            final int fromPosition = viewHolder.getAdapterPosition();
            final int toPosition = target.getAdapterPosition();
            if (fromPosition < toPosition) {
                for (int i = fromPosition; i < toPosition; i++) {
                    Collections.swap(mAdapter.getCapitolos(), i, i + 1);
                }
            } else {
                for (int i = fromPosition; i > toPosition; i--) {
                    Collections.swap(mAdapter.getCapitolos(), i, i - 1);
                }
            }
            mAdapter.notifyItemMoved(fromPosition, toPosition);
            return true;
        }

        @Override
        public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {
            MyViewHolder svH = (MyViewHolder ) viewHolder;
            int index = mAdapter.getCapitolos().indexOf(svH.currentItem);
            mAdapter.getCapitolos().remove(svH.currentItem);
            mAdapter.notifyItemRemoved(index);
            if (emptyView != null) {
                if (mAdapter.getCapitolos().size() > 0) {
                emptyView.setVisibility(TextView.GONE);
                } else {
                emptyView.setVisibility(TextView.VISIBLE);
                }
            }
        }

        @Override
        public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
            super.clearView(recyclerView, viewHolder);
            reorderData();
        }
    };

    ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleItemTouchCallback);
    itemTouchHelper.attachToRecyclerView(recList);

There is a support functions tahat make use of AsyncTask:

private void reorderData() {
    AsyncTask<String, Void, Spanned> task = new AsyncTask<String, Void, Spanned>() {
        @Override
        protected Spanned doInBackground(String... strings) {
            dbService.deleteAllData();
            for (int i = mAdapter.getCapitolos().size() - 1; i >= 0; i--) {
                Segnalibro s = mAdapter.getCapitolos().get(i);
                dbService.saveData(s.getIdCapitolo(), s.getVersetto());
            }
            return null;
        }

        @Override
        protected void onPostExecute(Spanned spanned) {
        }
    };
    task.execute();
}

Here, I've made a full sample in Kotlin (here), and, if you wish, you can enable swipe-to-dismiss on it . Here's the entire code of it:

build.gradle

implementation 'androidx.appcompat:appcompat:1.1.0-rc01'
implementation 'androidx.core:core-ktx:1.2.0-alpha02'
implementation 'androidx.constraintlayout:constraintlayout:2.0.0-beta2'
implementation 'com.google.android.material:material:1.1.0-alpha08'
implementation 'androidx.recyclerview:recyclerview:1.1.0-beta01'

grid_item.xml

<TextView
    android:id="@+id/textView" xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="100dp" android:gravity="center"/>

activity_main.xml

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView" tools:listitem="@layout/grid_item"  xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:orientation="vertical" app:spanCount="3" app:layoutManager="androidx.recyclerview.widget.GridLayoutManager"/>

manifest

<manifest package="com.sample.recyclerviewdraganddroptest" xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools">

    <application
        android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true"
        android:theme="@style/AppTheme.NoActionBar" tools:ignore="AllowBackup,GoogleAppIndexingWarning">
        <activity
            android:name=".MainActivity" android:label="@string/app_name" android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.kt

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val items = ArrayList<Int>(100)
        for (i in 0 until 100)
            items.add(i)
        recyclerView.adapter = object : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
            override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
                return object : RecyclerView.ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.grid_item, parent, false)) {}
            }

            override fun getItemCount() = items.size

            override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
                val data = items[position]
                holder.itemView.setBackgroundColor(if (data % 2 == 0) 0xffff0000.toInt() else 0xff00ff00.toInt())
                holder.itemView.textView.text = "item $data"
            }
        }
        val itemTouchHelper = ItemTouchHelper(object : ItemTouchHelper.Callback() {
            override fun isLongPressDragEnabled() = true
            override fun isItemViewSwipeEnabled() = false

            override fun getMovementFlags(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder): Int {
                val dragFlags = ItemTouchHelper.UP or ItemTouchHelper.DOWN or ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
                val swipeFlags = if (isItemViewSwipeEnabled) ItemTouchHelper.START or ItemTouchHelper.END else 0
                return makeMovementFlags(dragFlags, swipeFlags)
            }

            override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
                if (viewHolder.itemViewType != target.itemViewType)
                    return false
                val fromPosition = viewHolder.adapterPosition
                val toPosition = target.adapterPosition
                val item = items.removeAt(fromPosition)
                items.add(toPosition, item)
                recyclerView.adapter!!.notifyItemMoved(fromPosition, toPosition)
                return true
            }

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
                val position = viewHolder.adapterPosition
                items.remove(position)
                recyclerView.adapter!!.notifyItemRemoved(position)
            }

        })
        itemTouchHelper.attachToRecyclerView(recyclerView)
    }

}

Drag and drop items in RecyclerView with GridLayoutManager

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