Populate ViewPager with Loader

src/i2p/bote/ViewEmailActivity.java

@@ -3,21 +3,33 @@ package i2p.bote;
 import java.util.ArrayList;
 import java.util.List;
 
+import i2p.bote.email.Email;
+import i2p.bote.fileencryption.PasswordException;
 import i2p.bote.folder.EmailFolder;
+import i2p.bote.folder.FolderListener;
+import i2p.bote.util.BetterAsyncTaskLoader;
 import i2p.bote.util.BoteHelper;
+import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.app.FragmentStatePagerAdapter;
+import android.support.v4.app.LoaderManager;
+import android.support.v4.content.Loader;
 import android.support.v4.view.ViewPager;
 import android.support.v7.app.ActionBarActivity;
 
-public class ViewEmailActivity extends ActionBarActivity {
+public class ViewEmailActivity extends ActionBarActivity implements
+        LoaderManager.LoaderCallbacks<List<String>> {
     public static final String FOLDER_NAME = "folder_name";
     public static final String MESSAGE_ID = "message_id";
 
+    private static final int MESSAGE_ID_LIST_LOADER = 1;
+
     private EmailFolder mFolder;
+    // The messageId of the currently-viewed Email
+    private String mMessageId;
     private ViewPager mPager;
     private ViewEmailPagerAdapter mPagerAdapter;
 
@@ -30,21 +42,22 @@ public class ViewEmailActivity extends ActionBarActivity {
         String folderName = i.getStringExtra(FOLDER_NAME);
         mFolder = BoteHelper.getMailFolder(
                 folderName == null ? "inbox" : folderName);
-        String messageId = i.getStringExtra(MESSAGE_ID);
+        mMessageId = i.getStringExtra(MESSAGE_ID);
 
         // Instantiate the ViewPager and PagerAdapter
         mPager = (ViewPager) findViewById(R.id.pager);
         mPagerAdapter = new ViewEmailPagerAdapter(getSupportFragmentManager());
         mPager.setAdapter(mPagerAdapter);
+        mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
+            
+            @Override
+            public void onPageSelected(int position) {
+                mMessageId = mPagerAdapter.getMessageId(position);
+            }
+        });
 
-        // Start with a "fake" list of messageIds containing only
-        // the selected messageId, so the UI starts up quickly
-        List<String> messageIds = new ArrayList<String>();
-        messageIds.add(messageId);
-        mPagerAdapter.setData(messageIds);
-
-        // Now fire off a Loader to fetch the real list
-        // TODO: Implement
+        // Fire off a Loader to fetch the list of Emails
+        getSupportLoaderManager().initLoader(MESSAGE_ID_LIST_LOADER, null, this);
     }
 
     private class ViewEmailPagerAdapter extends FragmentStatePagerAdapter {
@@ -59,25 +72,27 @@ public class ViewEmailActivity extends ActionBarActivity {
             notifyDataSetChanged();
         }
 
+        public int getPosition(String messageId) {
+            if (mIds == null)
+                return 0;
+            else
+                return mIds.indexOf(messageId);
+        }
+
+        public String getMessageId(int position) {
+            if (mIds == null)
+                return null;
+            else
+                return mIds.get(position);
+        }
+
         @Override
         public Fragment getItem(int position) {
             if (mIds == null)
                 return null;
-
-            return ViewEmailFragment.newInstance(
-                    mFolder.getName(), mIds.get(position));
-        }
-
-        @Override
-        public int getItemPosition(Object item) {
-            ViewEmailFragment f = (ViewEmailFragment) item;
-            String messageId = f.getMessageId();
-            int position = mIds.indexOf(messageId);
-
-            if (position >= 0)
-                return position;
             else
-                return POSITION_NONE;
+                return ViewEmailFragment.newInstance(
+                        mFolder.getName(), mIds.get(position));
         }
 
         @Override
@@ -88,4 +103,68 @@ public class ViewEmailActivity extends ActionBarActivity {
                 return mIds.size();
         }
     }
+
+    // LoaderManager.LoaderCallbacks<List<String>>
+
+    public Loader<List<String>> onCreateLoader(int id, Bundle args) {
+        return new MessageIdListLoader(this, mFolder);
+    }
+
+    private static class MessageIdListLoader extends BetterAsyncTaskLoader<List<String>> implements
+    FolderListener {
+        private EmailFolder mFolder;
+
+        public MessageIdListLoader(Context context, EmailFolder folder) {
+            super(context);
+            mFolder = folder;
+        }
+
+        @Override
+        public List<String> loadInBackground() {
+            List<String> messageIds = null;
+            try {
+                List<Email> emails = BoteHelper.getEmails(mFolder, null, true);
+                messageIds = new ArrayList<String>();
+                for (Email email : emails)
+                    messageIds.add(email.getMessageID());
+            } catch (PasswordException pe) {
+                // TODO: Handle this error properly (get user to log in)
+            }
+            return messageIds;
+        }
+
+        protected void onStartMonitoring() {
+            mFolder.addFolderListener(this);
+        }
+
+        protected void onStopMonitoring() {
+            mFolder.removeFolderListener(this);
+        }
+
+        protected void releaseResources(List<String> data) {
+        }
+
+        // FolderListener
+
+        @Override
+        public void elementAdded() {
+            onContentChanged();
+        }
+
+        @Override
+        public void elementRemoved() {
+            onContentChanged();
+        }
+    }
+
+    public void onLoadFinished(Loader<List<String>> loader,
+            List<String> data) {
+        mPagerAdapter.setData(data);
+        mPager.setCurrentItem(
+                mPagerAdapter.getPosition(mMessageId));
+    }
+
+    public void onLoaderReset(Loader<List<String>> loader) {
+        mPagerAdapter.setData(null);
+    }
 }