Implement onStartLoading() in DeviceListLoader

Fixes #4641
Closes #5682
// FREEBIE

src/org/thoughtcrime/securesms/DeviceListFragment.java

@@ -77,7 +77,7 @@ public class DeviceListFragment extends ListFragment
   @Override
   public void onActivityCreated(Bundle bundle) {
     super.onActivityCreated(bundle);
-    getLoaderManager().initLoader(0, null, this).forceLoad();
+    getLoaderManager().initLoader(0, null, this);
     getListView().setOnItemClickListener(this);
   }
 
@@ -142,8 +142,7 @@ public class DeviceListFragment extends ListFragment
                               new DialogInterface.OnClickListener() {
       @Override
       public void onClick(DialogInterface dialog, int which) {
-        getLoaderManager().getLoader(0).forceLoad();
-        getLoaderManager().initLoader(0, null, DeviceListFragment.this);
+        getLoaderManager().restartLoader(0, null, DeviceListFragment.this);
       }
     });
 

src/org/thoughtcrime/securesms/database/loaders/DeviceListLoader.java

@@ -1,9 +1,9 @@
 package org.thoughtcrime.securesms.database.loaders;
 
 import android.content.Context;
-import android.support.v4.content.AsyncTaskLoader;
 import android.util.Log;
 
+import org.thoughtcrime.securesms.util.AsyncLoader;
 import org.whispersystems.signalservice.api.SignalServiceAccountManager;
 import org.whispersystems.signalservice.api.messages.multidevice.DeviceInfo;
 import org.whispersystems.signalservice.api.push.SignalServiceAddress;
@@ -14,7 +14,7 @@ import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;
 
-public class DeviceListLoader extends AsyncTaskLoader<List<DeviceInfo>> {
+public class DeviceListLoader extends AsyncLoader<List<DeviceInfo>> {
 
   private static final String TAG = DeviceListLoader.class.getSimpleName();
 

src/org/thoughtcrime/securesms/util/AsyncLoader.java

@@ -0,0 +1,80 @@
+package org.thoughtcrime.securesms.util;
+
+/*
+ * Copyright (C) 2011 Alexander Blom
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import android.support.v4.content.AsyncTaskLoader;
+import android.content.Context;
+
+/**
+ * Loader which extends AsyncTaskLoaders and handles caveats
+ * as pointed out in http://code.google.com/p/android/issues/detail?id=14944.
+ *
+ * Based on CursorLoader.java in the Fragment compatibility package
+ *
+ * @author Alexander Blom (me@alexanderblom.se)
+ *
+ * @param <D> data type
+ */
+public abstract class AsyncLoader<D> extends AsyncTaskLoader<D> {
+  private D data;
+
+  public AsyncLoader(Context context) {
+    super(context);
+  }
+
+  @Override
+  public void deliverResult(D data) {
+    if (isReset()) {
+      // An async query came in while the loader is stopped
+      return;
+    }
+
+    this.data = data;
+
+    super.deliverResult(data);
+  }
+
+
+  @Override
+  protected void onStartLoading() {
+    if (data != null) {
+      deliverResult(data);
+    }
+
+    if (takeContentChanged() || data == null) {
+      forceLoad();
+    }
+  }
+
+  @Override
+  protected void onStopLoading() {
+    // Attempt to cancel the current load task if possible.
+    cancelLoad();
+  }
+
+  @Override
+  protected void onReset() {
+    super.onReset();
+
+    // Ensure the loader is stopped
+    onStopLoading();
+
+    data = null;
+  }
+
+
+}