Merge pull request #64 from lukas1994/bugfix

Fixed bug in ParseQueryAdapter throwing IndexOutOfBoundsException.

Author: lukas1994

ParseLoginUI/src/androidTest/java/com/parse/ParseQueryAdapterTest.java

@@ -516,6 +516,57 @@ public void onLoaded(List<Thing> objects, Exception e) {
     assertTrue(done.tryAcquire(10, TimeUnit.SECONDS));
   }
 
+  public void testLoadNextPageBeforeLoadObjects() throws Exception {
+    final ParseQueryAdapter<Thing> adapter = new ParseQueryAdapter<>(activity, Thing.class);
+    final Semaphore done = new Semaphore(0);
+    adapter.addOnQueryLoadListener(new OnQueryLoadListener<Thing>() {
+      @Override
+      public void onLoading() {
+      }
+
+      @Override
+      public void onLoaded(List<Thing> objects, Exception e) {
+        assertNull(e);
+        assertEquals(TOTAL_THINGS, objects.size());
+        done.release();
+      }
+    });
+
+    adapter.loadNextPage();
+
+    // Make sure we assert in callback is executed
+    assertTrue(done.tryAcquire(10, TimeUnit.SECONDS));
+  }
+
+  public void testIncomingQueryResultAfterClearing() throws Exception {
+    final ParseQueryAdapter<Thing> adapter = new ParseQueryAdapter<>(activity, Thing.class);
+    final int pageSize = 4;
+    adapter.setObjectsPerPage(pageSize);
+    final Semaphore done = new Semaphore(0);
+    final Capture<Integer> timesThrough = new Capture<>(0);
+    adapter.addOnQueryLoadListener(new OnQueryLoadListener<Thing>() {
+      @Override
+      public void onLoading() {}
+
+      @Override
+      public void onLoaded(List<Thing> objects, Exception e) {
+        switch (timesThrough.get()) {
+        case 0:
+          adapter.loadNextPage();
+          adapter.clear();
+        case 1:
+          done.release();
+        }
+        timesThrough.set(timesThrough.get()+1);
+      }
+    });
+
+    adapter.loadObjects();
+
+    // Make sure we assert in callback is executed
+    assertTrue(done.tryAcquire(10, TimeUnit.SECONDS));
+  }
+
   public void testLoadObjectsWithOverrideSetPageOnQuery() throws Exception {
     final int arbitraryLimit = 3;
     final ParseQueryAdapter<Thing> adapter =

ParseLoginUI/src/main/java/com/parse/ParseQueryAdapter.java

@@ -21,7 +21,6 @@
 
 package com.parse;
 
-import android.annotation.SuppressLint;
 import android.content.Context;
 import android.database.DataSetObserver;
 import android.graphics.drawable.Drawable;
@@ -36,9 +35,12 @@
 import com.parse.ParseQuery.CachePolicy;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.WeakHashMap;
+import java.util.concurrent.ConcurrentHashMap;
 
 import bolts.Capture;
 
@@ -142,6 +144,9 @@ public static interface OnQueryLoadListener<T extends ParseObject> {
 
   private List<T> objects = new ArrayList<>();
 
+  private Set<ParseQuery> runningQueries = Collections.newSetFromMap(new ConcurrentHashMap<ParseQuery, Boolean>());
+
+
   // Used to keep track of the pages of objects when using CACHE_THEN_NETWORK. When using this,
   // the data will be flattened and put into the objects list.
   private List<List<T>> objectPages = new ArrayList<>();
@@ -332,11 +337,19 @@ public void unregisterDataSetObserver(DataSetObserver observer) {
    */
   public void clear() {
     this.objectPages.clear();
+    cancelAllQueries();
     syncObjectsWithPages();
     this.notifyDataSetChanged();
     this.currentPage = 0;
   }
 
+  private void cancelAllQueries() {
+    for (ParseQuery q : runningQueries) {
+      q.cancel();
+    }
+    runningQueries.clear();
+  }
+
   /**
    * Clears the table and loads the first page of objects asynchronously. This method is called
    * automatically when this {@code Adapter} is attached to an {@code AdapterView}.
@@ -365,22 +378,36 @@ private void loadObjects(final int page, final boolean shouldClear) {
     // In the case of CACHE_THEN_NETWORK, two callbacks will be called. Using this flag to keep track,
     final Capture<Boolean> firstCallBack = new Capture<>(true);
 
+    runningQueries.add(query);
+
+    // TODO convert to Tasks and CancellationTokens
+    // (depends on https://github.com/ParsePlatform/Parse-SDK-Android/issues/6)
     query.findInBackground(new FindCallback<T>() {
-      @SuppressLint("ShowToast")
       @Override
       public void done(List<T> foundObjects, ParseException e) {
+        if (!runningQueries.contains(query)) {
+          return;
+        }
+        // In the case of CACHE_THEN_NETWORK, two callbacks will be called. We can only remove the
+        // query after the second callback.
+        if (query.getCachePolicy() != CachePolicy.CACHE_THEN_NETWORK ||
+                (query.getCachePolicy() == CachePolicy.CACHE_THEN_NETWORK && !firstCallBack.get())) {
+          runningQueries.remove(query);
+        }
         if ((!Parse.isLocalDatastoreEnabled() &&
-            query.getCachePolicy() == CachePolicy.CACHE_ONLY)
-            && (e != null) && e.getCode() == ParseException.CACHE_MISS) {
+                query.getCachePolicy() == CachePolicy.CACHE_ONLY)
+                && (e != null) && e.getCode() == ParseException.CACHE_MISS) {
           // no-op on cache miss
           return;
         }
 
-        if ((e != null)
-            && ((e.getCode() == ParseException.CONNECTION_FAILED) || (e.getCode() != ParseException.CACHE_MISS))) {
+        if ((e != null) && ((e.getCode() == ParseException.CONNECTION_FAILED) || (e.getCode() != ParseException.CACHE_MISS))) {
           hasNextPage = true;
         } else if (foundObjects != null) {
           if (shouldClear && firstCallBack.get()) {
+            runningQueries.remove(query);
+            cancelAllQueries();
+            runningQueries.add(query); // allow 2nd callback
             objectPages.clear();
             objectPages.add(new ArrayList<T>());
             currentPage = page;
@@ -432,7 +459,12 @@ private void syncObjectsWithPages() {
    * changed.
    */
   public void loadNextPage() {
-    this.loadObjects(currentPage + 1, false);
+    if (objects.size() == 0 && runningQueries.size() == 0) {
+      loadObjects(0, false);
+    }
+    else {
+      loadObjects(currentPage + 1, false);
+    }
   }
 
   /**