Improved the way posts are retrieved on LatestPostsFragment

app/src/main/java/org/communiquons/android/comunic/client/data/asynctasks/SafeAsyncTask.java

@@ -50,6 +50,15 @@ public abstract class SafeAsyncTask<Params, Progress, Result>
         this.onPostExecuteListener = onPostExecuteListener;
     }
 
+    /**
+     * Check whether the a OnPostExecuteListener has been set or not
+     *
+     * @return TRUE if it has been set / FALSE else
+     */
+    public boolean hasOnPostExecuteListener(){
+        return this.onPostExecuteListener != null;
+    }
+
     @Override
     protected void onPostExecute(Result result) {
         super.onPostExecute(result);

app/src/main/java/org/communiquons/android/comunic/client/ui/asynctasks/GetLatestPostsTask.java

@@ -0,0 +1,34 @@
+package org.communiquons.android.comunic.client.ui.asynctasks;
+
+import android.content.Context;
+
+import org.communiquons.android.comunic.client.data.arrays.PostsList;
+import org.communiquons.android.comunic.client.data.asynctasks.SafeAsyncTask;
+import org.communiquons.android.comunic.client.data.helpers.GetUsersHelper;
+import org.communiquons.android.comunic.client.data.helpers.PostsHelper;
+
+/**
+ * Get latest posts task
+ *
+ * @author Pierre HUBERT
+ */
+public class GetLatestPostsTask extends SafeAsyncTask<Integer, Void, PostsList> {
+
+    public GetLatestPostsTask(Context context) {
+        super(context);
+    }
+
+    @Override
+    protected PostsList doInBackground(Integer... integers) {
+
+        //Get the list of posts
+        int from  = integers[0] == 0 ? -1 : integers[0];
+        PostsList list = new PostsHelper(getContext()).get_latest(from);
+        if(list == null) return null;
+
+        list.setUsersInfo(new GetUsersHelper(getContext()).getMultiple(list.getUsersId()));
+        if(!list.hasUsersInfo()) return null;
+
+        return list;
+    }
+}

app/src/main/java/org/communiquons/android/comunic/client/ui/fragments/LatestPostsFragment.java

@@ -16,10 +16,12 @@ import android.widget.Toast;
 
 import org.communiquons.android.comunic.client.R;
 import org.communiquons.android.comunic.client.data.arrays.PostsList;
+import org.communiquons.android.comunic.client.data.asynctasks.SafeAsyncTask;
 import org.communiquons.android.comunic.client.data.helpers.GetUsersHelper;
 import org.communiquons.android.comunic.client.data.helpers.PostsHelper;
 import org.communiquons.android.comunic.client.data.models.UserInfo;
 import org.communiquons.android.comunic.client.ui.activities.MainActivity;
+import org.communiquons.android.comunic.client.ui.asynctasks.GetLatestPostsTask;
 import org.communiquons.android.comunic.client.ui.listeners.OnPostListFragmentsUpdateListener;
 
 /**
@@ -37,27 +39,21 @@ public class LatestPostsFragment extends Fragment
      */
     private static final String TAG = "LatestPostsFragment";
 
-    /**
-     * Posts helper
-     */
-    PostsHelper mPostsHelper;
-
-    /**
-     * User information helper
-     */
-    GetUsersHelper mUserHelper;
-
     /**
      * The list of posts
      */
     PostsList mPostsList;
 
-
     /**
      * Fragment that displays the list of posts
      */
     private PostsListFragment mPostsListFragment;
 
+    /**
+     * Load posts task
+     */
+    private GetLatestPostsTask mGetLatestPostsTask;
+
     /**
      * Loading progress bar
      */
@@ -68,21 +64,6 @@ public class LatestPostsFragment extends Fragment
      */
     TextView mNoPostNotice;
 
-    /**
-     * Posts load lock
-     */
-    private boolean mLoadPostsLock = false;
-
-    @Override
-    public void onStart() {
-        super.onStart();
-
-        //Create posts helper
-        mPostsHelper = new PostsHelper(getActivity());
-
-        //Create user helper
-        mUserHelper = new GetUsersHelper(getActivity());
-    }
 
     @Nullable
     @Override
@@ -110,6 +91,45 @@ public class LatestPostsFragment extends Fragment
         //Refresh the list of posts of the user
         if(mPostsList == null)
             refresh_posts_list();
+        else {
+            mPostsListFragment = null;
+            show_posts_list();
+        }
+    }
+
+    @Override
+    public void onStop() {
+        super.onStop();
+
+        unset_all_load_tasks();
+    }
+
+    @Override
+    public void onSaveInstanceState(@NonNull Bundle outState) {
+        super.onSaveInstanceState(outState);
+        unset_all_load_tasks();
+    }
+
+    /**
+     * Unset all pending load tasks
+     */
+    private void unset_all_load_tasks(){
+        if(mGetLatestPostsTask != null)
+            mGetLatestPostsTask.setOnPostExecuteListener(null);
+    }
+
+    /**
+     * Check whether are being loaded now or not
+     *
+     * @return TRUE if some posts are loading / FALSE else
+     */
+    private boolean is_loading_posts() {
+
+        return mGetLatestPostsTask != null &&
+                mGetLatestPostsTask.hasOnPostExecuteListener() &&
+                !mGetLatestPostsTask.isCancelled() &&
+                mGetLatestPostsTask.getStatus() != AsyncTask.Status.FINISHED;
+
     }
 
     /**
@@ -122,29 +142,15 @@ public class LatestPostsFragment extends Fragment
         toggleNoPostNoticeVisibility(false);
 
         //Get the list of latest posts
-        new AsyncTask<Void, Void, PostsList>(){
+        unset_all_load_tasks();
+        mGetLatestPostsTask = new GetLatestPostsTask(getActivity());
+        mGetLatestPostsTask.setOnPostExecuteListener(new SafeAsyncTask.OnPostExecuteListener<PostsList>() {
             @Override
-            protected PostsList doInBackground(Void... params) {
+            public void OnPostExecute(PostsList posts) {
-                PostsList postsList =  mPostsHelper.get_latest();
-
-                //Get user information, if possible
-                if(postsList != null)
-                    postsList.setUsersInfo(mUserHelper.getMultiple(postsList.getUsersId()));
-
-                return postsList;
-            }
-
-            @Override
-            protected void onPostExecute(PostsList posts) {
-
-                //Check if the activity still exists or not
-                if(getActivity() == null)
-                    return;
-
                 on_got_new_posts_list(posts);
             }
-        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+        });
-
+        mGetLatestPostsTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 0);
     }
 
     /**
@@ -168,14 +174,27 @@ public class LatestPostsFragment extends Fragment
         }
 
         //Save the list of posts
+        if (mPostsList == null)
             mPostsList = list;
+        else {
+            mPostsList.addAll(list);
+            assert mPostsList.getUsersInfo() != null;
+            mPostsList.getUsersInfo().putAll(list.getUsersInfo());
+        }
 
-        //Check if the posts list is empty
+        show_posts_list();
-        if(mPostsList.size() == 0)
+    }
-            toggleNoPostNoticeVisibility(true);
 
+    /**
+     * Show posts list
+     */
+    private void show_posts_list(){
+
+        //Hide loading bar
+        toggleLoadingBarVisibility(false);
+
+        if(mPostsListFragment == null){
 
-        //Append the new posts list
             //Apply the post fragment
             mPostsListFragment = new PostsListFragment();
             mPostsListFragment.setPostsList(mPostsList);
@@ -186,6 +205,43 @@ public class LatestPostsFragment extends Fragment
             transaction.replace(R.id.posts_list_target, mPostsListFragment);
             transaction.commit();
         }
+        else
+            //Append the new posts list
+            mPostsListFragment.show();
+
+        //Check if the posts list is empty
+        toggleNoPostNoticeVisibility(mPostsList.size() == 0);
+    }
+
+    @Override
+    public void onLoadMorePosts() {
+
+        //Check if post loading is already locked
+        if(is_loading_posts())
+            return;
+
+        if(mPostsList == null)
+            return;
+
+        if(mPostsList.size() == 0)
+            return;
+
+        //Display loading bar
+        toggleLoadingBarVisibility(true);
+
+        //Get the ID of the oldest post to start from
+        int start = mPostsList.get(mPostsList.size()-1).getId() - 1;
+
+        //Get older posts
+        mGetLatestPostsTask = new GetLatestPostsTask(getActivity());
+        mGetLatestPostsTask.setOnPostExecuteListener(new SafeAsyncTask.OnPostExecuteListener<PostsList>() {
+            @Override
+            public void OnPostExecute(PostsList posts) {
+                on_got_new_posts_list(posts);
+            }
+        });
+        mGetLatestPostsTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, start);
+    }
 
     /**
      * Toggle progress bar visibility
@@ -204,85 +260,4 @@ public class LatestPostsFragment extends Fragment
     private void toggleNoPostNoticeVisibility(boolean visible){
         mNoPostNotice.setVisibility(visible ? View.VISIBLE : View.GONE);
     }
-
-    @Override
-    public void onLoadMorePosts() {
-
-        //Check if post loading is already locked
-        if(mLoadPostsLock)
-            return;
-
-        if(mPostsList == null)
-            return;
-
-        if(mPostsList.size() == 0)
-            return;
-
-        //Display loading bar
-        mLoadPostsLock = true;
-        toggleLoadingBarVisibility(true);
-
-        //Get the ID of the oldest post to start from
-        final int start = mPostsList.get(mPostsList.size()-1).getId() - 1;
-
-        //Get older posts
-        new GetOlderPosts().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, start);
-    }
-
-    /**
-     * This class get and apply older posts
-     */
-    private class GetOlderPosts extends AsyncTask<Integer, Void, PostsList> {
-
-        @Override
-        protected PostsList doInBackground(Integer... id) {
-
-            //Get the list of older posts
-            PostsList postsList = mPostsHelper.get_latest(id[0]);
-
-            //Check for errors
-            if(postsList == null)
-                return null;
-
-            //Get information about the users
-            ArrayMap<Integer, UserInfo> usersInfo
-                    = mUserHelper.getMultiple(postsList.getUsersId());
-
-            //Check for errors
-            if(usersInfo == null)
-                return null;
-
-            assert postsList.getUsersInfo() != null;
-            postsList.getUsersInfo().putAll(usersInfo);
-
-            return postsList;
-        }
-
-        @Override
-        protected void onPostExecute(PostsList posts) {
-
-            //Check if the activity has been detached
-            if(getActivity() == null)
-                return;
-
-
-            //Unlock post loading
-            mLoadPostsLock = false;
-            toggleLoadingBarVisibility(false);
-
-            if(posts == null){
-                Toast.makeText(getActivity(), R.string.err_get_older_posts,
-                        Toast.LENGTH_SHORT).show();
-                return;
-            }
-
-            mPostsList.addAll(posts);
-            assert mPostsList.getUsersInfo() != null;
-            mPostsList.getUsersInfo().putAll(posts.getUsersInfo());
-
-            //Apply new posts list
-            mPostsListFragment.show();
-
-        }
-    }
 }