Delete messages by swiping and add snackbar for undoing deletion.

app/src/main/java/com/github/gotify/messages/ListMessageAdapter.java

@@ -5,10 +5,10 @@
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
-import android.widget.BaseAdapter;
 import android.widget.ImageButton;
 import android.widget.ImageView;
 import android.widget.TextView;
+import androidx.annotation.NonNull;
 import androidx.recyclerview.widget.RecyclerView;
 import butterknife.BindView;
 import butterknife.ButterKnife;
@@ -25,7 +25,7 @@
 import io.noties.markwon.movement.MovementMethodPlugin;
 import java.util.List;
 
-public class ListMessageAdapter extends BaseAdapter {
+public class ListMessageAdapter extends RecyclerView.Adapter<ListMessageAdapter.ViewHolder> {
 
     private Context content;
     private Picasso picasso;
@@ -56,34 +56,25 @@ public class ListMessageAdapter extends BaseAdapter {
                         .build();
     }
 
-    void items(List<MessageWithImage> items) {
-        this.items = items;
+    public MessageWithImage getItem(int position) {
+        return items.get(position);
     }
 
-    @Override
-    public int getCount() {
-        return items.size();
+    void items(List<MessageWithImage> items) {
+        this.items = items;
     }
 
+    @NonNull
     @Override
-    public MessageWithImage getItem(int position) {
-        return items.get(position);
-    }
+    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
+        View view = LayoutInflater.from(content).inflate(R.layout.message_item, parent, false);
 
-    @Override
-    public long getItemId(int position) {
-        return getItem(position).message.getId();
+        ViewHolder holder = new ViewHolder(view);
+        return holder;
     }
 
     @Override
-    public View getView(int position, View convertView, ViewGroup parent) {
-        final View view;
-        if (convertView == null) {
-            view = LayoutInflater.from(content).inflate(R.layout.message_item, parent, false);
-        } else {
-            view = convertView;
-        }
-        ViewHolder holder = new ViewHolder(view);
+    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
         final MessageWithImage message = items.get(position);
         if (Extras.useMarkdown(message.message)) {
             holder.message.setAutoLinkMask(0);
@@ -102,8 +93,17 @@ public View getView(int position, View convertView, ViewGroup parent) {
                         ? Utils.dateToRelative(message.message.getDate())
                         : "?");
         holder.delete.setOnClickListener((ignored) -> delete.delete(message.message));
+    }
 
-        return view;
+    @Override
+    public int getItemCount() {
+        return items.size();
+    }
+
+    @Override
+    public long getItemId(int position) {
+        MessageWithImage currentItem = items.get(position);
+        return currentItem.message.getId();
     }
 
     static class ViewHolder extends RecyclerView.ViewHolder {

app/src/main/java/com/github/gotify/messages/MessagesActivity.java

@@ -6,23 +6,31 @@
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.graphics.Canvas;
+import android.graphics.drawable.ColorDrawable;
+import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
-import android.widget.AbsListView;
 import android.widget.ImageButton;
-import android.widget.ListView;
 import android.widget.TextView;
 import android.widget.ViewFlipper;
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.appcompat.app.AlertDialog;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
+import androidx.core.content.ContextCompat;
+import androidx.core.graphics.drawable.DrawableCompat;
 import androidx.core.view.GravityCompat;
 import androidx.drawerlayout.widget.DrawerLayout;
+import androidx.recyclerview.widget.DividerItemDecoration;
+import androidx.recyclerview.widget.ItemTouchHelper;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
 import butterknife.BindView;
 import butterknife.ButterKnife;
@@ -66,7 +74,7 @@
 import static java.util.Collections.emptyList;
 
 public class MessagesActivity extends AppCompatActivity
-        implements NavigationView.OnNavigationItemSelectedListener, AbsListView.OnScrollListener {
+        implements NavigationView.OnNavigationItemSelectedListener {
 
     private BroadcastReceiver receiver =
             new BroadcastReceiver() {
@@ -90,7 +98,7 @@ public void onReceive(Context context, Intent intent) {
     NavigationView navigationView;
 
     @BindView(R.id.messages_view)
-    ListView messagesView;
+    RecyclerView messagesView;
 
     @BindView(R.id.swipe_refresh)
     SwipeRefreshLayout swipeRefreshLayout;
@@ -137,9 +145,21 @@ protected void onCreate(Bundle savedInstanceState) {
 
         messages = new MessageFacade(client.createService(MessageApi.class), appsHolder);
 
-        messagesView.setOnScrollListener(this);
-        messagesView.setAdapter(
-                new ListMessageAdapter(this, settings, picasso, emptyList(), this::delete));
+        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
+        DividerItemDecoration dividerItemDecoration =
+                new DividerItemDecoration(
+                        messagesView.getContext(), layoutManager.getOrientation());
+        ListMessageAdapter adapter =
+                new ListMessageAdapter(this, settings, picasso, emptyList(), this::delete);
+
+        messagesView.addItemDecoration(dividerItemDecoration);
+        messagesView.setHasFixedSize(true);
+        messagesView.setLayoutManager(layoutManager);
+        messagesView.addOnScrollListener(new MessageListOnScrollListener());
+        messagesView.setAdapter(adapter);
+
+        ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new SwipeToDeleteCallback(adapter));
+        itemTouchHelper.attachToRecyclerView(messagesView);
 
         swipeRefreshLayout.setOnRefreshListener(this::onRefresh);
         drawer.addDrawerListener(
@@ -341,18 +361,118 @@ protected void onDestroy() {
         picasso.shutdown();
     }
 
-    @Override
-    public void onScrollStateChanged(AbsListView view, int scrollState) {}
+    private class SwipeToDeleteCallback extends ItemTouchHelper.SimpleCallback {
+        private ListMessageAdapter adapter;
+        private Drawable icon;
+        private final ColorDrawable background;
 
-    @Override
-    public void onScroll(
-            AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
-        if (firstVisibleItem + visibleItemCount > totalItemCount - 15
-                && totalItemCount != 0
-                && messages.canLoadMore(appId)) {
-            if (!isLoadMore) {
-                isLoadMore = true;
-                new LoadMore().execute(appId);
+        public SwipeToDeleteCallback(ListMessageAdapter adapter) {
+            super(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT);
+            this.adapter = adapter;
+
+            int backgroundColorId =
+                    ContextCompat.getColor(MessagesActivity.this, R.color.swipeBackground);
+            int iconColorId = ContextCompat.getColor(MessagesActivity.this, R.color.swipeIcon);
+
+            Drawable drawable =
+                    ContextCompat.getDrawable(MessagesActivity.this, R.drawable.ic_delete);
+            if (drawable != null) {
+                icon = DrawableCompat.wrap(drawable.mutate());
+                DrawableCompat.setTint(icon, iconColorId);
+            }
+
+            background = new ColorDrawable(backgroundColorId);
+        }
+
+        @Override
+        public boolean onMove(
+                @NonNull RecyclerView recyclerView,
+                @NonNull RecyclerView.ViewHolder viewHolder,
+                @NonNull RecyclerView.ViewHolder target) {
+            return false;
+        }
+
+        @Override
+        public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
+            int position = viewHolder.getAdapterPosition();
+            Message message = adapter.getItem(position).message;
+            MessagesActivity.this.delete(message);
+        }
+
+        @Override
+        public void onChildDraw(
+                @NonNull Canvas c,
+                @NonNull RecyclerView recyclerView,
+                @NonNull RecyclerView.ViewHolder viewHolder,
+                float dX,
+                float dY,
+                int actionState,
+                boolean isCurrentlyActive) {
+            View itemView = viewHolder.itemView;
+
+            int iconHeight = itemView.getHeight() / 3;
+            double scale = iconHeight / (double) icon.getIntrinsicHeight();
+            int iconWidth = (int) (icon.getIntrinsicWidth() * scale);
+
+            int iconMarginLeftRight = 50;
+            int iconMarginTopBottom = (itemView.getHeight() - iconHeight) / 2;
+            int iconTop = itemView.getTop() + iconMarginTopBottom;
+            int iconBottom = itemView.getBottom() - iconMarginTopBottom;
+
+            if (dX > 0) {
+                // Swiping to the right
+                int iconLeft = itemView.getLeft() + iconMarginLeftRight;
+                int iconRight = itemView.getLeft() + iconMarginLeftRight + iconWidth;
+                icon.setBounds(iconLeft, iconTop, iconRight, iconBottom);
+
+                background.setBounds(
+                        itemView.getLeft(),
+                        itemView.getTop(),
+                        itemView.getLeft() + ((int) dX),
+                        itemView.getBottom());
+            } else if (dX < 0) {
+                // Swiping to the left
+                int iconLeft = itemView.getRight() - iconMarginLeftRight - iconWidth;
+                int iconRight = itemView.getRight() - iconMarginLeftRight;
+                icon.setBounds(iconLeft, iconTop, iconRight, iconBottom);
+
+                background.setBounds(
+                        itemView.getRight() + ((int) dX),
+                        itemView.getTop(),
+                        itemView.getRight(),
+                        itemView.getBottom());
+            } else {
+                // View is unswiped
+                icon.setBounds(0, 0, 0, 0);
+                background.setBounds(0, 0, 0, 0);
+            }
+
+            background.draw(c);
+            icon.draw(c);
+
+            super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
+        }
+    }
+
+    private class MessageListOnScrollListener extends RecyclerView.OnScrollListener {
+        @Override
+        public void onScrollStateChanged(RecyclerView view, int scrollState) {}
+
+        @Override
+        public void onScrolled(RecyclerView view, int dx, int dy) {
+            LinearLayoutManager linearLayoutManager = (LinearLayoutManager) view.getLayoutManager();
+            if (linearLayoutManager != null) {
+                int lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
+                int totalItemCount = view.getAdapter().getItemCount();
+
+                if (lastVisibleItem > totalItemCount - 15
+                        && totalItemCount != 0
+                        && messages.canLoadMore(appId)) {
+                    if (!isLoadMore) {
+                        isLoadMore = true;
+                        new LoadMore().execute(appId);
+                    }
+                }
             }
         }
     }

app/src/main/res/layout/activity_messages.xml

@@ -30,13 +30,13 @@
                     android:layout_width="match_parent"
                     android:layout_height="match_parent" >
 
-                    <ListView
+                    <androidx.recyclerview.widget.RecyclerView
                         android:id="@+id/messages_view"
                         android:layout_width="match_parent"
                         android:layout_height="match_parent"
                         android:scrollbars="vertical"
                         app:layout_behavior="@string/appbar_scrolling_view_behavior">
-                    </ListView>
+                    </androidx.recyclerview.widget.RecyclerView>
 
                     <androidx.constraintlayout.widget.ConstraintLayout
                         android:id="@+id/no_messages"

app/src/main/res/layout/message_item.xml

@@ -4,7 +4,8 @@
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical"
-    android:padding="10dp">
+    android:padding="10dp"
+    android:background="?android:colorBackground">
 
     <TextView
         android:id="@+id/message_date"

app/src/main/res/values/colors.xml

@@ -4,4 +4,6 @@
     <color name="colorPrimaryDark">#3867d6</color>
     <color name="colorAccent">#1c49b4</color>
     <color name="icons">#434343</color>
+    <color name="swipeBackground">#E91E1E</color>
+    <color name="swipeIcon">#FFFFFF</color>
 </resources>