Adds item fading with swipe

Author: iPaulPro

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

@@ -50,6 +50,7 @@ public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
     @Override
     public void onBindViewHolder(final ItemViewHolder holder, int position) {
         holder.textView.setText(mItems.get(position));
+
         holder.handleView.setOnTouchListener(new View.OnTouchListener() {
             @Override
             public boolean onTouch(View v, MotionEvent event) {

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

@@ -1,31 +1,39 @@
 package co.paulburke.android.itemtouchhelperdemo.helper;
 
 import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.helper.ItemTouchHelper;
 
 /**
- * Interface to notify a {@link RecyclerView.Adapter} of moving and dismissal event from a {@link
- * android.support.v7.widget.helper.ItemTouchHelper.Callback}.
+ * Interface to listen for a move or dismissal event from a {@link ItemTouchHelper.Callback}.
  *
  * @author Paul Burke (ipaulpro)
  */
 public interface ItemTouchHelperAdapter {
 
     /**
      * Called when an item has been dragged far enough to trigger a move. This is called every time
-     * an item is shifted, and not at the end of a "drop" event.
+     * an item is shifted, and <strong>not</strong> at the end of a "drop" event.<br/>
+     * <br/>
+     * Implementations should call {@link RecyclerView.Adapter#notifyItemMoved(int, int)} after
+     * adjusting the underlying data to reflect this move.
      *
      * @param fromPosition The start position of the moved item.
-     * @param toPosition   Then end position of the moved item.
+     * @param toPosition   Then resolved position of the moved item.
+     *
      * @see RecyclerView#getAdapterPositionFor(RecyclerView.ViewHolder)
      * @see RecyclerView.ViewHolder#getAdapterPosition()
      */
     void onItemMove(int fromPosition, int toPosition);
 
 
     /**
-     * Called when an item has been dismissed by a swipe.
+     * Called when an item has been dismissed by a swipe.<br/>
+     * <br/>
+     * Implementations should call {@link RecyclerView.Adapter#notifyItemRemoved(int)} after
+     * adjusting the underlying data to reflect this removal.
      *
      * @param position The position of the item dismissed.
+     *
      * @see RecyclerView#getAdapterPositionFor(RecyclerView.ViewHolder)
      * @see RecyclerView.ViewHolder#getAdapterPosition()
      */

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

@@ -1,13 +1,14 @@
 package co.paulburke.android.itemtouchhelperdemo.helper;
 
+import android.graphics.Canvas;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.helper.ItemTouchHelper;
 
 /**
  * An implementation of {@link ItemTouchHelper.Callback} that enables basic drag & drop and
  * swipe-to-dismiss. Drag events are automatically started by an item long-press.<br/>
  * </br/>
- * Expects the <code>RecyclerView.Adapter</code> to react to {@link
+ * Expects the <code>RecyclerView.Adapter</code> to listen for {@link
  * ItemTouchHelperAdapter} callbacks and the <code>RecyclerView.ViewHolder</code> to implement
  * {@link ItemTouchHelperViewHolder}.
  *
@@ -53,6 +54,17 @@ public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
         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);
+
+        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);
+        }
+    }
+
     @Override
     public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
         if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
@@ -67,6 +79,8 @@ 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);
+
         ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
         itemViewHolder.onItemClear();
     }