actually use iterator interface for ParcelableFileCache in activities

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/ImportKeysActivity.java

@@ -39,6 +39,7 @@ import android.view.ViewGroup;
 import org.sufficientlysecure.keychain.Constants;
 import org.sufficientlysecure.keychain.R;
 import org.sufficientlysecure.keychain.api.OpenKeychainIntents;
+import org.sufficientlysecure.keychain.ui.ImportKeysListFragment.IteratorWithSize;
 import org.sufficientlysecure.keychain.ui.util.FormattingUtils;
 import org.sufficientlysecure.keychain.ui.util.KeyFormattingUtils;
 import org.sufficientlysecure.keychain.util.Preferences;
@@ -481,15 +482,17 @@ public class ImportKeysActivity extends ActionBarActivity {
             Bundle data = new Bundle();
 
             // get DATA from selected key entries
-            ArrayList<ParcelableKeyRing> selectedEntries = mListFragment.getSelectedData();
+            IteratorWithSize<ParcelableKeyRing> selectedEntries = mListFragment.getSelectedData();
 
-            // instead of given the entries by Intent extra, cache them into a file
-            // to prevent Java Binder problems on heavy imports
+            // instead of giving the entries by Intent extra, cache them into a
+            // file to prevent Java Binder problems on heavy imports
             // read FileImportCache for more info.
             try {
+                // We parcel this iteratively into a file - anything we can
+                // display here, we should be able to import.
                 ParcelableFileCache<ParcelableKeyRing> cache =
                         new ParcelableFileCache<ParcelableKeyRing>(this, "key_import.pcl");
-                cache.writeCache(selectedEntries.size(), selectedEntries.iterator());
+                cache.writeCache(selectedEntries.getSize(), selectedEntries);
 
                 intent.putExtra(KeychainIntentService.EXTRA_DATA, data);
 

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/ImportKeysListFragment.java

@@ -48,6 +48,7 @@ import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 
 public class ImportKeysListFragment extends ListFragment implements
@@ -74,12 +75,42 @@ public class ImportKeysListFragment extends ListFragment implements
         return mAdapter.getData();
     }
 
-    public ArrayList<ParcelableKeyRing> getSelectedData() {
-        ArrayList<ParcelableKeyRing> result = new ArrayList<ParcelableKeyRing>();
-        for (ImportKeysListEntry entry : getSelectedEntries()) {
-            result.add(mCachedKeyData.get(entry.hashCode()));
-        }
-        return result;
+    // Tuples would make this easier...
+    public static interface IteratorWithSize<E> extends Iterator<E> {
+        int getSize();
+    }
+
+    /** Returns an Iterator (with size) of the selected data items.
+     * This iterator is sort of a tradeoff, it's slightly more complex than an
+     * ArrayList would have been, but we save some memory by just returning
+     * relevant elements on demand.
+     */
+    public IteratorWithSize<ParcelableKeyRing> getSelectedData() {
+        final ArrayList<ImportKeysListEntry> entries = getSelectedEntries();
+        final Iterator<ImportKeysListEntry> it = entries.iterator();
+        return new IteratorWithSize<ParcelableKeyRing>() {
+
+            @Override
+            public int getSize() {
+                return entries.size();
+            }
+
+            @Override
+            public boolean hasNext() {
+                return it.hasNext();
+            }
+
+            @Override
+            public ParcelableKeyRing next() {
+                // throws NoSuchElementException if it doesn't exist, but that's not our problem
+                return mCachedKeyData.get(it.next().hashCode());
+            }
+
+            @Override
+            public void remove() {
+                it.remove();
+            }
+        };
     }
 
     public ArrayList<ImportKeysListEntry> getSelectedEntries() {

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/adapter/ImportKeysAdapter.java

@@ -41,7 +41,6 @@ import org.sufficientlysecure.keychain.ui.util.KeyFormattingUtils;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
@@ -91,17 +90,13 @@ public class ImportKeysAdapter extends ArrayAdapter<ImportKeysListEntry> {
     }
 
     public ArrayList<ImportKeysListEntry> getSelectedEntries() {
-        ArrayList<ImportKeysListEntry> selectedData = new ArrayList<ImportKeysListEntry>();
-        // Nothing to select, nvm.
-        if (mData == null) {
-            return selectedData;
-        }
+        ArrayList<ImportKeysListEntry> result = new ArrayList<ImportKeysListEntry>();
         for (ImportKeysListEntry entry : mData) {
             if (entry.isSelected()) {
-                selectedData.add(entry);
+                result.add(entry);
             }
         }
-        return selectedData;
+        return result;
     }
 
     @Override

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/ParcelableFileCache.java

@@ -55,6 +55,10 @@ public class ParcelableFileCache<E extends Parcelable> {
         mFilename = filename;
     }
 
+    /** This method returns the number of entries as valid for the iterator
+     * received by the latest readCache operation. Yes, it is slightly
+     * peculiar.
+     */
     public int getNumEntries() {
         return mNumEntries;
     }
@@ -107,7 +111,7 @@ public class ParcelableFileCache<E extends Parcelable> {
             throw new IOException(e);
         }
 
-        // yes this is slightly sloppy data flow. WE WOULDN'T NEED THIS WITH TUPLE RETURN TYPES
+        // yes this is sloppy data flow. WE WOULDN'T NEED THIS WITH TUPLE RETURN TYPES
         mNumEntries = ois.readInt();
 
         return new Iterator<E>() {