Update ListView sample to utilize ParseQueryPager

ParseUI-Widget-Sample/src/main/java/com/parse/ui/widget/sample/ListActivity.java

@@ -1,23 +1,29 @@
 package com.parse.ui.widget.sample;
 
+import android.database.DataSetObserver;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.v7.app.AppCompatActivity;
-import android.util.Log;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.BaseAdapter;
 import android.widget.ListView;
-import android.widget.Toast;
+import android.widget.ProgressBar;
+import android.widget.TextView;
 
+import com.parse.FindCallback;
 import com.parse.ParseException;
 import com.parse.ParseObject;
 import com.parse.ParseQuery;
-import com.parse.ParseQueryAdapter;
+import com.parse.widget.util.ParseQueryPager;
 
 import java.util.List;
 
+import bolts.CancellationTokenSource;
 
-public class ListActivity extends AppCompatActivity {
 
-  private static final String TAG = "ListActivity";
+public class ListActivity extends AppCompatActivity {
 
   @Override
   protected void onCreate(@Nullable Bundle savedInstanceState) {
@@ -26,32 +32,205 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
 
     ListView listView = (ListView) findViewById(R.id.list);
 
-    ParseQueryAdapter<ParseObject> adapter = new ParseQueryAdapter<>(this,
-        new ParseQueryAdapter.QueryFactory<ParseObject>() {
-          @Override
-          public ParseQuery<ParseObject> create() {
-            return ParseQuery.getQuery("Contact")
-                .orderByAscending("name")
-                .setCachePolicy(ParseQuery.CachePolicy.CACHE_THEN_NETWORK);
+    MyAdapter<ParseObject> adapter = new MyAdapter<>(createPager());
+    listView.setAdapter(adapter);
+  }
+
+  private ParseQueryPager<ParseObject> createPager() {
+    ParseQuery<ParseObject> query = ParseQuery.getQuery("TestObject");
+    query.orderByAscending("name");
+    query.setCachePolicy(ParseQuery.CachePolicy.CACHE_THEN_NETWORK);
+    return new ParseQueryPager<>(query, 25);
+  }
+
+  public static class MyAdapter<T extends ParseObject> extends BaseAdapter {
+
+    public static final int TYPE_ITEM = 0;
+    public static final int TYPE_NEXT = 1;
+
+    private static class ItemViewHolder extends ViewHolder {
+      TextView textView;
+
+      public ItemViewHolder(View itemView) {
+        super(itemView);
+        textView = (TextView) itemView;
+      }
+    }
+
+    private static class NextViewHolder extends ViewHolder {
+      TextView textView;
+      ProgressBar progressBar;
+
+      public NextViewHolder(View itemView) {
+        super(itemView);
+        textView = (TextView) itemView.findViewById(android.R.id.text1);
+        progressBar = (ProgressBar) itemView.findViewById(android.R.id.progress);
+      }
+
+      public void setLoading(boolean loading) {
+        if (loading) {
+          textView.setVisibility(View.INVISIBLE);
+          progressBar.setVisibility(View.VISIBLE);
+          progressBar.setIndeterminate(true);
+        } else {
+          textView.setVisibility(View.VISIBLE);
+          progressBar.setVisibility(View.INVISIBLE);
+          progressBar.setIndeterminate(false);
+        }
+      }
+    }
+
+    private final Object lock = new Object();
+    private ParseQueryPager<T> pager;
+    private CancellationTokenSource cts;
+
+    public MyAdapter(ParseQueryPager<T> pager) {
+      swap(pager);
+    }
+
+    public ParseQueryPager<T> getPager() {
+      synchronized (lock) {
+        return pager;
+      }
+    }
+
+    public void swap(ParseQueryPager<T> pager) {
+      synchronized (lock) {
+        if (cts != null) {
+          cts.cancel();
+        }
+        this.pager = pager;
+        this.cts = new CancellationTokenSource();
+      }
+    }
+
+    private void loadNextPage() {
+      final ParseQueryPager<T> pager;
+      final CancellationTokenSource cts;
+
+      synchronized (lock) {
+        pager = this.pager;
+        cts = this.cts;
+      }
+
+      // Utilizing callbacks to support CACHE_THEN_NETWORK
+      pager.loadNextPage(new FindCallback<T>() {
+        @Override
+        public void done(List<T> results, ParseException e) {
+          if (results == null && e == null) { // cancelled
+            return;
+          }
+
+          if (e != null) {
+            notifyDataSetChanged();
+            return;
           }
-        }, android.R.layout.simple_list_item_1);
-    adapter.setTextKey("name");
-    adapter.addOnQueryLoadListener(new ParseQueryAdapter.OnQueryLoadListener<ParseObject>() {
-      @Override
-      public void onLoading() {
-        Log.d(TAG, "loading");
-      }
-
-      @Override
-      public void onLoaded(List<ParseObject> objects, Exception e) {
-        Log.d(TAG, "loaded");
-        if (e != null
-            && e instanceof ParseException
-            && ((ParseException) e).getCode() != ParseException.CACHE_MISS) {
-          Toast.makeText(ListActivity.this, "Error: " + e.getMessage(), Toast.LENGTH_LONG).show();
+
+          notifyDataSetChanged();
         }
+      }, cts.getToken());
+      notifyDataSetChanged();
+    }
+
+    @Override
+    public int getCount() {
+      ParseQueryPager<T> pager = getPager();
+      return pager.getObjects().size() + (pager.hasNextPage() ? 1 : 0);
+    }
+
+    @Override
+    public T getItem(int position) {
+      List<T> objects = getPager().getObjects();
+      return position < objects.size() ? objects.get(position) : null;
+    }
+
+    @Override
+    public long getItemId(int position) {
+      return position;
+    }
+
+    @Override
+    public final View getView(int position, View convertView, ViewGroup parent) {
+      ViewHolder holder;
+      View view;
+      if (convertView == null) {
+        holder = onCreateViewHolder(parent, getItemViewType(position));
+        view = holder.itemView;
+        view.setTag(holder);
+      } else {
+        view = convertView;
+        holder = (ViewHolder) view.getTag();
       }
-    });
-    listView.setAdapter(adapter);
+      onBindViewHolder(holder, position);
+      return view;
+    }
+
+    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+      LayoutInflater inflater = LayoutInflater.from(parent.getContext());
+      switch (viewType) {
+        case TYPE_ITEM: {
+          View v = inflater.inflate(android.R.layout.simple_list_item_1, parent, false);
+          return new ItemViewHolder(v);
+        }
+        case TYPE_NEXT: {
+          View v = inflater.inflate(R.layout.load_more_list_item, parent, false);
+          v.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+              if (!getPager().isLoadingNextPage()) {
+                loadNextPage();
+              }
+            }
+          });
+          NextViewHolder vh = new NextViewHolder(v);
+          vh.textView.setText(R.string.load_more);
+          return vh;
+        }
+        default:
+          throw new IllegalStateException("Invalid view type: " + viewType);
+      }
+    }
+
+    public void onBindViewHolder(ViewHolder holder, int position) {
+      switch (getItemViewType(position)) {
+        case TYPE_ITEM: {
+          ParseObject item = getItem(position);
+
+          ItemViewHolder vh = (ItemViewHolder) holder;
+          vh.textView.setText(item.getString("name"));
+        }
+        break;
+        case TYPE_NEXT: {
+          NextViewHolder vh = (NextViewHolder) holder;
+          vh.setLoading(getPager().isLoadingNextPage());
+        }
+        break;
+      }
+    }
+
+    @Override
+    public int getViewTypeCount() {
+      return 2;
+    }
+
+    @Override
+    public int getItemViewType(int position) {
+      return position < getPager().getObjects().size() ? TYPE_ITEM : TYPE_NEXT;
+    }
+
+    @Override
+    public void registerDataSetObserver(DataSetObserver observer) {
+      super.registerDataSetObserver(observer);
+      // We use this method as a notification that the ListView is bound to the adapter.
+      loadNextPage();
+    }
+
+    public static class ViewHolder {
+      private View itemView;
+
+      public ViewHolder(View itemView) {
+        this.itemView = itemView;
+      }
+    }
   }
 }

ParseUI-Widget-Sample/src/main/res/layout/load_more_list_item.xml

@@ -0,0 +1,19 @@
+<?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="wrap_content"
+    android:paddingStart="?android:attr/listPreferredItemPaddingStart"
+    android:paddingEnd="?android:attr/listPreferredItemPaddingEnd"
+    android:minHeight="?android:attr/listPreferredItemHeightSmall" >
+    <TextView
+        android:id="@android:id/text1"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:textAppearance="?android:attr/textAppearanceListItemSmall"
+        android:layout_gravity="center_vertical" />
+    <ProgressBar
+        android:id="@android:id/progress"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"/>
+</FrameLayout>

ParseUI-Widget-Sample/src/main/res/values/strings.xml

@@ -1,4 +1,6 @@
 <resources>
     <string name="app_name">ParseUI-Widget Sample</string>
     <string name="list_name">ListView Sample</string>
+
+    <string name="load_more">Load more…</string>
 </resources>