Better text filter for ChooseFolder (folder is displayed if search term is found anywhere in the folder name, not just at the beginning)

Heavily based on a patch provided by Marcus.Wolschon

Fixes issue 2098

src/com/fsck/k9/activity/ChooseFolder.java

@@ -9,6 +9,7 @@ import android.view.View;
 import android.view.Window;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
+import android.widget.Filter;
 import android.widget.ListView;
 import android.widget.TextView;
 import com.fsck.k9.*;
@@ -26,7 +27,7 @@ public class ChooseFolder extends K9ListActivity
     String mSelectFolder;
     Account mAccount;
     MessageReference mMessageReference;
-    ArrayAdapter<String> adapter;
+    ArrayAdapter<String> mAdapter;
     private ChooseFolderHandler mHandler = new ChooseFolderHandler();
     String heldInbox = null;
     boolean hideCurrentFolder = true;
@@ -49,7 +50,6 @@ public class ChooseFolder extends K9ListActivity
 
         requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
         getListView().setFastScrollEnabled(true);
-        getListView().setTextFilterEnabled(true);
         getListView().setItemsCanFocus(false);
         getListView().setChoiceMode(ListView.CHOICE_MODE_NONE);
         Intent intent = getIntent();
@@ -73,13 +73,25 @@ public class ChooseFolder extends K9ListActivity
         if (mFolder == null)
             mFolder = "";
 
-        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
+        mAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1)
+        {
+            private Filter myFilter = null;
 
-        setListAdapter(adapter);
+            @Override
+            public Filter getFilter()
+            {
+                if (myFilter == null)
+                {
+                    myFilter = new FolderListFilter<String>(this);
+                }
+                return myFilter;
+            }
+        };
+
+        setListAdapter(mAdapter);
 
 
-        MessagingController.getInstance(getApplication()).listFolders(mAccount,
-                false, mListener);
+        MessagingController.getInstance(getApplication()).listFolders(mAccount, false, mListener);
 
 
         this.getListView().setOnItemClickListener(new AdapterView.OnItemClickListener()
@@ -120,7 +132,14 @@ public class ChooseFolder extends K9ListActivity
                     setProgressBarIndeterminateVisibility(msg.arg1 != 0);
                     break;
                 case MSG_DATA_CHANGED:
-                    adapter.notifyDataSetChanged();
+                    mAdapter.notifyDataSetChanged();
+
+                    /*
+                     * Only enable the text filter after the list has been
+                     * populated to avoid possible race conditions because our
+                     * FolderListFilter isn't really thread-safe.
+                     */
+                    getListView().setTextFilterEnabled(true);
                     break;
                 case MSG_SET_SELECTED_FOLDER:
                     getListView().setSelection(msg.arg1);
@@ -261,20 +280,20 @@ public class ChooseFolder extends K9ListActivity
                     return aName.compareToIgnoreCase(bName);
                 }
             });
-            adapter.setNotifyOnChange(false);
-            adapter.clear();
+            mAdapter.setNotifyOnChange(false);
+            mAdapter.clear();
             int selectedFolder = -1;
             int position = 0;
             for (String name : localFolders)
             {
                 if (K9.INBOX.equalsIgnoreCase(name))
                 {
-                    adapter.add(getString(R.string.special_mailbox_name_inbox));
+                    mAdapter.add(getString(R.string.special_mailbox_name_inbox));
                     heldInbox = name;
                 }
                 else
                 {
-                    adapter.add(name);
+                    mAdapter.add(name);
                 }
 
                 if (mSelectFolder != null)

src/com/fsck/k9/activity/FolderListFilter.java

@@ -0,0 +1,138 @@
+package com.fsck.k9.activity;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import android.util.Log;
+import android.widget.ArrayAdapter;
+import android.widget.Filter;
+
+import com.fsck.k9.K9;
+
+/**
+ * Filter to search for occurences of the search-expression in any place of the
+ * folder-name instead of doing jsut a prefix-search.
+ *
+ * @author Marcus@Wolschon.biz
+ */
+public class FolderListFilter<T> extends Filter
+{
+    /**
+     * ArrayAdapter that contains the list of folders displayed in the
+     * ListView.
+     * This object is modified by {@link #publishResults} to reflect the
+     * changes due to the filtering performed by {@link #performFiltering}.
+     * This in turn will change the folders displayed in the ListView.
+     */
+    private ArrayAdapter<T> mFolders;
+
+    /**
+     * All folders.
+     */
+    private ArrayList<T> mOriginalValues = null;
+
+    /**
+     * Create a filter for a list of folders.
+     *
+     * @param folderNames
+     */
+    public FolderListFilter(final ArrayAdapter<T> folderNames)
+    {
+        this.mFolders = folderNames;
+    }
+
+    /**
+     * Do the actual search.
+     * {@inheritDoc}
+     *
+     * @see #publishResults(CharSequence, FilterResults)
+     */
+    @Override
+    protected FilterResults performFiltering(CharSequence searchTerm)
+    {
+        FilterResults results = new FilterResults();
+
+        // Copy the values from mFolders to mOriginalValues if this is the
+        // first time this method is called.
+        if (mOriginalValues == null)
+        {
+            int count = mFolders.getCount();
+            mOriginalValues = new ArrayList<T>(count);
+            for (int i = 0; i < count; i++)
+            {
+                mOriginalValues.add(mFolders.getItem(i));
+            }
+        }
+
+        if ((searchTerm == null) || (searchTerm.length() == 0))
+        {
+            ArrayList<T> list = new ArrayList<T>(mOriginalValues);
+            results.values = list;
+            results.count = list.size();
+        }
+        else
+        {
+            final String searchTermString = searchTerm.toString().toLowerCase();
+            final String[] words = searchTermString.split(" ");
+            final int wordCount = words.length;
+
+            final ArrayList<T> values = mOriginalValues;
+            final int count = values.size();
+
+            final ArrayList<T> newValues = new ArrayList<T>();
+
+            for (int i = 0; i < count; i++)
+            {
+                final T value = values.get(i);
+                final String valueText = value.toString().toLowerCase();
+
+                for (int k = 0; k < wordCount; k++)
+                {
+                    if (valueText.contains(words[k]))
+                    {
+                        newValues.add(value);
+                        break;
+                    }
+                }
+            }
+
+            results.values = newValues;
+            results.count = newValues.size();
+        }
+
+        return results;
+    }
+
+    /**
+     * Publish the results to the user-interface.
+     * {@inheritDoc}
+     */
+    @SuppressWarnings("unchecked")
+    @Override
+    protected void publishResults(CharSequence constraint, FilterResults results)
+    {
+        // Don't notify for every change
+        mFolders.setNotifyOnChange(false);
+
+        //noinspection unchecked
+        final List<T> folders = (List<T>) results.values;
+        mFolders.clear();
+        if (folders != null)
+        {
+            for (T folder : folders)
+            {
+                if (folder != null)
+                {
+                    mFolders.add(folder);
+                }
+            }
+        }
+        else
+        {
+            Log.w(K9.LOG_TAG, "FolderListFilter.publishResults - null search-result ");
+        }
+
+        // Send notification that the data set changed now
+        mFolders.notifyDataSetChanged();
+    }
+}