More doc and comments

Author: iPaulPro

app/src/main/java/co/paulburke/android/itemtouchhelperdemo/RecyclerListAdapter.java

@@ -34,24 +34,36 @@
 import co.paulburke.android.itemtouchhelperdemo.helper.ItemTouchHelperViewHolder;
 
 /**
+ * Simple RecyclerView.Adapter that implements {@link ItemTouchHelperAdapter} to respond to move and
+ * dismiss events from a {@link android.support.v7.widget.helper.ItemTouchHelper}.
+ *
  * @author Paul Burke (ipaulpro)
  */
 public class RecyclerListAdapter extends RecyclerView.Adapter<RecyclerListAdapter.ItemViewHolder>
         implements ItemTouchHelperAdapter {
 
+    /**
+     * Listener for manual initiation of a drag.
+     */
+    public interface OnStartDragListener {
+
+        /**
+         * Called when a view is requesting a start of a drag.
+         *
+         * @param viewHolder The holder of the view to drag.
+         */
+        void onStartDrag(RecyclerView.ViewHolder viewHolder);
+    }
+
     private static final String[] STRINGS = new String[]{
             "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"
     };
 
-    public interface OnDragStartListener {
-        void onDragStarted(RecyclerView.ViewHolder viewHolder);
-    }
-
     private final List<String> mItems = new ArrayList<>();
 
-    private final OnDragStartListener mDragStartListener;
+    private final OnStartDragListener mDragStartListener;
 
-    public RecyclerListAdapter(OnDragStartListener dragStartListener) {
+    public RecyclerListAdapter(OnStartDragListener dragStartListener) {
         mDragStartListener = dragStartListener;
         mItems.addAll(Arrays.asList(STRINGS));
     }
@@ -67,11 +79,12 @@ public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
     public void onBindViewHolder(final ItemViewHolder holder, int position) {
         holder.textView.setText(mItems.get(position));
 
+        // Start a drag whenever the handle view it touched
         holder.handleView.setOnTouchListener(new View.OnTouchListener() {
             @Override
             public boolean onTouch(View v, MotionEvent event) {
                 if (MotionEventCompat.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
-                    mDragStartListener.onDragStarted(holder);
+                    mDragStartListener.onStartDrag(holder);
                 }
                 return false;
             }
@@ -96,6 +109,10 @@ public int getItemCount() {
         return mItems.size();
     }
 
+    /**
+     * Simple example of a view holder that implements {@link ItemTouchHelperViewHolder} and has a
+     * "handle" view that initiates a drag event when touched.
+     */
     public static class ItemViewHolder extends RecyclerView.ViewHolder implements
             ItemTouchHelperViewHolder {
 

app/src/main/java/co/paulburke/android/itemtouchhelperdemo/RecyclerListFragment.java

@@ -31,7 +31,7 @@
 /**
  * @author Paul Burke (ipaulpro)
  */
-public class RecyclerListFragment extends Fragment implements RecyclerListAdapter.OnDragStartListener {
+public class RecyclerListFragment extends Fragment implements RecyclerListAdapter.OnStartDragListener {
 
     private ItemTouchHelper mItemTouchHelper;
 
@@ -61,7 +61,7 @@ public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
     }
 
     @Override
-    public void onDragStarted(RecyclerView.ViewHolder viewHolder) {
+    public void onStartDrag(RecyclerView.ViewHolder viewHolder) {
         mItemTouchHelper.startDrag(viewHolder);
     }
 }

app/src/main/java/co/paulburke/android/itemtouchhelperdemo/helper/SimpleItemTouchHelperCallback.java

@@ -19,6 +19,7 @@
 import android.graphics.Canvas;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.helper.ItemTouchHelper;
+import android.view.View;
 
 /**
  * An implementation of {@link ItemTouchHelper.Callback} that enables basic drag & drop and
@@ -32,6 +33,8 @@
  */
 public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {
 
+    public static final float ALPHA_FULL = 1.0f;
+
     private final ItemTouchHelperAdapter mAdapter;
 
     public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter) {
@@ -50,6 +53,7 @@ public boolean isItemViewSwipeEnabled() {
 
     @Override
     public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
+        // Enable drag and swipe in both directions
         final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
         final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;
         return makeMovementFlags(dragFlags, swipeFlags);
@@ -61,29 +65,33 @@ public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder source,
             return false;
         }
 
+        // Notify the adapter of the move
         mAdapter.onItemMove(source.getAdapterPosition(), target.getAdapterPosition());
         return true;
     }
 
     @Override
     public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
+        // Notify the adapter of the dismissal
         mAdapter.onItemDismiss(viewHolder.getAdapterPosition());
     }
 
     @Override
     public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
         super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
 
+        // Fade out the view as it is swiped out of the parent's bounds
         if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
-            final float itemWidth = (float) viewHolder.itemView.getWidth();
-            final float alpha = 1.0f - Math.abs(dX) / itemWidth;
-            viewHolder.itemView.setAlpha(alpha);
+            View itemView = viewHolder.itemView;
+            final float alpha = ALPHA_FULL - Math.abs(dX) / (float) itemView.getWidth();
+            itemView.setAlpha(alpha);
         }
     }
 
     @Override
     public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
         if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
+            // Let the view holder know that this item is being moved or dragged
             ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
             itemViewHolder.onItemSelected();
         }
@@ -95,8 +103,9 @@ public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionStat
     public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
         super.clearView(recyclerView, viewHolder);
 
-        viewHolder.itemView.setAlpha(1.0f);
+        viewHolder.itemView.setAlpha(ALPHA_FULL);
 
+        // Tell the view holder it's time to restore the idle state
         ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
         itemViewHolder.onItemClear();
     }