improve performance of adapter implementations by caching index, use data uri where possible in ViewKeyActivity

OpenPGP-Keychain/res/menu/key_list_secret_multi.xml

@@ -3,7 +3,7 @@
 
     <item
         android:id="@+id/menu_key_list_public_multi_delete"
-        android:icon="@android:drawable/ic_menu_delete"
+        android:icon="@drawable/ic_action_discard"
         android:title="@string/menu_delete_key"/>
 
 </menu>

OpenPGP-Keychain/res/values/strings.xml

@@ -183,10 +183,10 @@
     <string name="enter_passphrase_twice">Enter the passphrase twice.</string>
     <string name="select_encryption_key">Select at least one encryption key.</string>
     <string name="select_encryption_or_signature_key">Select at least one encryption key or a signature key.</string>
-    <string name="specify_file_to_encrypt_to">Please specify which file to encrypt to.\nWARNING! File will be overwritten if it exists.</string>
+    <string name="specify_file_to_encrypt_to">Please specify which file to encrypt to.\nWARNING: File will be overwritten if it exists.</string>
-    <string name="specify_file_to_decrypt_to">Please specify which file to decrypt to.\nWARNING! File will be overwritten if it exists.</string>
+    <string name="specify_file_to_decrypt_to">Please specify which file to decrypt to.\nWARNING: File will be overwritten if it exists.</string>
-    <string name="specify_file_to_export_to">Please specify which file to export to.\nWARNING! File will be overwritten if it exists.</string>
+    <string name="specify_file_to_export_to">Please specify which file to export to.\nWARNING: File will be overwritten if it exists.</string>
-    <string name="specify_file_to_export_secret_keys_to">Please specify which file to export to.\nWARNING! You are about to export SECRET keys.\nWARNING! File will be overwritten if it exists.</string>
+    <string name="specify_file_to_export_secret_keys_to">Please specify which file to export to.\nWARNING: You are about to export SECRET keys.\nWARNING: File will be overwritten if it exists.</string>
     <string name="key_deletion_confirmation">Do you really want to delete the key \'%s\'?\nYou can\'t undo this!</string>
     <string name="key_deletion_confirmation_multi">Do you really want to delete all selected keys?\nYou can\'t undo this!</string>
     <string name="secret_key_deletion_confirmation">Do you really want to delete the SECRET key \'%s\'?\nYou can\'t undo this!</string>

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/pgp/PgpKeyHelper.java

@@ -447,7 +447,7 @@ public class PgpKeyHelper {
         }
 
         default: {
-            algorithmStr = "???";
+            algorithmStr = "Unknown";
             break;
         }
         }
@@ -510,7 +510,7 @@ public class PgpKeyHelper {
     }
 
     /**
-     * TODO: what is the difference to the other function?
+     * TODO: documentation
      * 
      * @param keyId
      * @return

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/KeyListPublicFragment.java

@@ -94,7 +94,7 @@ public class KeyListPublicFragment extends Fragment implements AdapterView.OnIte
             public void onClick(View v) {
                 Intent intentImportFromFile = new Intent(getActivity(), ImportKeysActivity.class);
                 intentImportFromFile.setAction(ImportKeysActivity.ACTION_IMPORT_KEY_FROM_FILE);
-                startActivityForResult(intentImportFromFile, Id.request.import_from_qr_code);
+                startActivityForResult(intentImportFromFile, 0);
             }
         });
 

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/KeyListSecretActivity.java

@@ -68,8 +68,9 @@ public class KeyListSecretActivity extends DrawerActivity {
 
             return true;
         case R.id.menu_key_list_secret_import:
-            Intent intentImport = new Intent(this, ImportKeysActivity.class);
+            Intent intentImportFromFile = new Intent(this, ImportKeysActivity.class);
-            startActivityForResult(intentImport, Id.request.import_from_qr_code);
+            intentImportFromFile.setAction(ImportKeysActivity.ACTION_IMPORT_KEY_FROM_FILE);
+            startActivityForResult(intentImportFromFile, 0);
 
             return true;
         default:

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/ViewKeyActivity.java

@@ -77,8 +77,6 @@ public class ViewKeyActivity extends SherlockFragmentActivity implements CreateN
 
     private Uri mDataUri;
 
-    private PGPPublicKey mPublicKey;
-
     private TextView mName;
     private TextView mEmail;
     private TextView mComment;
@@ -200,36 +198,16 @@ public class ViewKeyActivity extends SherlockFragmentActivity implements CreateN
     }
 
     private void loadData(Uri dataUri) {
-        // TODO: don't use pubkey object, use database!!!
-
-        PGPPublicKeyRing ring = (PGPPublicKeyRing) ProviderHelper.getPGPKeyRing(this, dataUri);
-        mPublicKey = ring.getPublicKey();
-
-        mKeyId.setText(PgpKeyHelper.shortifyFingerprint(PgpKeyHelper
-                .convertFingerprintToHex(mPublicKey.getFingerprint())));
-
-        String fingerprint = PgpKeyHelper.convertFingerprintToHex(mPublicKey.getFingerprint());
-        fingerprint = fingerprint.replace("  ", "\n");
-        mFingerprint.setText(fingerprint);
-
-        // TODO: get image with getUserAttributes() on key and then PGPUserAttributeSubpacketVector
-
-        Date expiryDate = PgpKeyHelper.getExpiryDate(mPublicKey);
-        if (expiryDate == null) {
-            mExpiry.setText(R.string.none);
-        } else {
-            mExpiry.setText(DateFormat.getDateFormat(getApplicationContext()).format(expiryDate));
-        }
-
-        mCreation.setText(DateFormat.getDateFormat(getApplicationContext()).format(
-                PgpKeyHelper.getCreationDate(mPublicKey)));
-        mAlgorithm.setText(PgpKeyHelper.getAlgorithmInfo(mPublicKey));
-
         mActionEncrypt.setOnClickListener(new OnClickListener() {
 
             @Override
             public void onClick(View v) {
-                long[] encryptionKeyIds = new long[] { mPublicKey.getKeyID() };
+                // TODO: don't get object here!!! solve this differently!
+                PGPPublicKeyRing ring = (PGPPublicKeyRing) ProviderHelper.getPGPKeyRing(
+                        ViewKeyActivity.this, mDataUri);
+                PGPPublicKey publicKey = ring.getPublicKey();
+
+                long[] encryptionKeyIds = new long[] { publicKey.getKeyID() };
                 Intent intent = new Intent(ViewKeyActivity.this, EncryptActivity.class);
                 intent.setAction(EncryptActivity.ACTION_ENCRYPT);
                 intent.putExtra(EncryptActivity.EXTRA_ENCRYPTION_KEY_IDS, encryptionKeyIds);
@@ -262,6 +240,9 @@ public class ViewKeyActivity extends SherlockFragmentActivity implements CreateN
 
     static final String[] KEYRING_PROJECTION = new String[] { KeyRings._ID, KeyRings.MASTER_KEY_ID,
             UserIds.USER_ID };
+    static final int KEYRING_INDEX_ID = 0;
+    static final int KEYRING_INDEX_MASTER_KEY_ID = 1;
+    static final int KEYRING_INDEX_USER_ID = 2;
 
     static final String[] USER_IDS_PROJECTION = new String[] { UserIds._ID, UserIds.USER_ID,
             UserIds.RANK, };
@@ -271,8 +252,18 @@ public class ViewKeyActivity extends SherlockFragmentActivity implements CreateN
 
     static final String[] KEYS_PROJECTION = new String[] { Keys._ID, Keys.KEY_ID,
             Keys.IS_MASTER_KEY, Keys.ALGORITHM, Keys.KEY_SIZE, Keys.CAN_CERTIFY, Keys.CAN_SIGN,
-            Keys.CAN_ENCRYPT, };
+            Keys.CAN_ENCRYPT, Keys.CREATION, Keys.EXPIRY };
     static final String KEYS_SORT_ORDER = Keys.RANK + " ASC";
+    static final int KEYS_INDEX_ID = 0;
+    static final int KEYS_INDEX_KEY_ID = 1;
+    static final int KEYS_INDEX_IS_MASTER_KEY = 2;
+    static final int KEYS_INDEX_ALGORITHM = 3;
+    static final int KEYS_INDEX_KEY_SIZE = 4;
+    static final int KEYS_INDEX_CAN_CERTIFY = 5;
+    static final int KEYS_INDEX_CAN_SIGN = 6;
+    static final int KEYS_INDEX_CAN_ENCRYPT = 7;
+    static final int KEYS_INDEX_CREATION = 8;
+    static final int KEYS_INDEX_EXPIRY = 9;
 
     public Loader<Cursor> onCreateLoader(int id, Bundle args) {
         switch (id) {
@@ -310,7 +301,9 @@ public class ViewKeyActivity extends SherlockFragmentActivity implements CreateN
         switch (loader.getId()) {
         case LOADER_ID_KEYRING:
             if (data.moveToFirst()) {
-                String[] mainUserId = PgpKeyHelper.splitUserId(data.getString(2));
+                // get name, email, and comment from USER_ID
+                String[] mainUserId = PgpKeyHelper.splitUserId(data
+                        .getString(KEYRING_INDEX_USER_ID));
                 setTitle(mainUserId[0]);
                 mName.setText(mainUserId[0]);
                 mEmail.setText(mainUserId[1]);
@@ -322,6 +315,50 @@ public class ViewKeyActivity extends SherlockFragmentActivity implements CreateN
             mUserIdsAdapter.swapCursor(data);
             break;
         case LOADER_ID_KEYS:
+            // the first key here is our master key
+            if (data.moveToFirst()) {
+                // get key id from MASTER_KEY_ID
+                String keyId = "0x"
+                        + PgpKeyHelper.convertKeyIdToHex(data.getLong(KEYS_INDEX_KEY_ID));
+                mKeyId.setText(keyId);
+
+                if (data.isNull(KEYS_INDEX_CREATION)) {
+                    mCreation.setText(R.string.none);
+                } else {
+                    Date creationDate = new Date(data.getLong(KEYS_INDEX_CREATION) * 1000);
+
+                    mCreation.setText(DateFormat.getDateFormat(getApplicationContext()).format(
+                            creationDate));
+                }
+
+                if (data.isNull(KEYS_INDEX_EXPIRY)) {
+                    mExpiry.setText(R.string.none);
+                } else {
+                    Date expiryDate = new Date(data.getLong(KEYS_INDEX_EXPIRY) * 1000);
+
+                    mExpiry.setText(DateFormat.getDateFormat(getApplicationContext()).format(
+                            expiryDate));
+                }
+
+                String algorithmStr = PgpKeyHelper.getAlgorithmInfo(
+                        data.getInt(KEYS_INDEX_ALGORITHM), data.getInt(KEYS_INDEX_KEY_SIZE));
+                mAlgorithm.setText(algorithmStr);
+
+                // TODO: Don't get key object here!!!
+                // put fingerprint in database?
+                PGPPublicKeyRing ring = (PGPPublicKeyRing) ProviderHelper.getPGPKeyRing(this,
+                        mDataUri);
+                PGPPublicKey publicKey = ring.getPublicKey();
+
+                String fingerprint = PgpKeyHelper.convertFingerprintToHex(publicKey
+                        .getFingerprint());
+                fingerprint = fingerprint.replace("  ", "\n");
+                mFingerprint.setText(fingerprint);
+
+                // TODO: get image with getUserAttributes() on key and then
+                // PGPUserAttributeSubpacketVector
+            }
+
             mKeysAdapter.swapCursor(data);
             break;
 

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/adapter/KeyListPublicAdapter.java

@@ -43,6 +43,7 @@ import android.widget.TextView;
 public class KeyListPublicAdapter extends CursorAdapter implements StickyListHeadersAdapter {
     private LayoutInflater mInflater;
     private int mSectionColumnIndex;
+    private int mIndexUserId;
 
     @SuppressLint("UseSparseArrays")
     private HashMap<Integer, Boolean> mSelection = new HashMap<Integer, Boolean>();
@@ -52,6 +53,26 @@ public class KeyListPublicAdapter extends CursorAdapter implements StickyListHea
 
         mInflater = LayoutInflater.from(context);
         mSectionColumnIndex = sectionColumnIndex;
+        initIndex(c);
+    }
+    
+    @Override
+    public Cursor swapCursor(Cursor newCursor) {
+        initIndex(newCursor);
+
+        return super.swapCursor(newCursor);
+    }
+
+    /**
+     * Get column indexes for performance reasons just once in constructor and swapCursor. For a
+     * performance comparison see http://stackoverflow.com/a/17999582
+     * 
+     * @param cursor
+     */
+    private void initIndex(Cursor cursor) {
+        if (cursor != null) {
+            mIndexUserId = cursor.getColumnIndexOrThrow(UserIds.USER_ID);
+        }
     }
 
     /**
@@ -62,14 +83,12 @@ public class KeyListPublicAdapter extends CursorAdapter implements StickyListHea
      */
     @Override
     public void bindView(View view, Context context, Cursor cursor) {
-        int userIdIndex = cursor.getColumnIndex(UserIds.USER_ID);
-
         TextView mainUserId = (TextView) view.findViewById(R.id.mainUserId);
         mainUserId.setText(R.string.unknown_user_id);
         TextView mainUserIdRest = (TextView) view.findViewById(R.id.mainUserIdRest);
         mainUserIdRest.setText("");
 
-        String userId = cursor.getString(userIdIndex);
+        String userId = cursor.getString(mIndexUserId);
         if (userId != null) {
             String[] userIdSplit = PgpKeyHelper.splitUserId(userId);
 

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/adapter/KeyListSecretAdapter.java

@@ -37,6 +37,8 @@ import android.widget.TextView;
 public class KeyListSecretAdapter extends CursorAdapter {
     private LayoutInflater mInflater;
 
+    private int mIndexUserId;
+
     @SuppressLint("UseSparseArrays")
     private HashMap<Integer, Boolean> mSelection = new HashMap<Integer, Boolean>();
 
@@ -44,18 +46,36 @@ public class KeyListSecretAdapter extends CursorAdapter {
         super(context, c, flags);
 
         mInflater = LayoutInflater.from(context);
+        initIndex(c);
+    }
+
+    @Override
+    public Cursor swapCursor(Cursor newCursor) {
+        initIndex(newCursor);
+
+        return super.swapCursor(newCursor);
+    }
+
+    /**
+     * Get column indexes for performance reasons just once in constructor and swapCursor. For a
+     * performance comparison see http://stackoverflow.com/a/17999582
+     * 
+     * @param cursor
+     */
+    private void initIndex(Cursor cursor) {
+        if (cursor != null) {
+            mIndexUserId = cursor.getColumnIndexOrThrow(UserIds.USER_ID);
+        }
     }
 
     @Override
     public void bindView(View view, Context context, Cursor cursor) {
-        int userIdIndex = cursor.getColumnIndex(UserIds.USER_ID);
-
         TextView mainUserId = (TextView) view.findViewById(R.id.mainUserId);
         mainUserId.setText(R.string.unknown_user_id);
         TextView mainUserIdRest = (TextView) view.findViewById(R.id.mainUserIdRest);
         mainUserIdRest.setText("");
 
-        String userId = cursor.getString(userIdIndex);
+        String userId = cursor.getString(mIndexUserId);
         if (userId != null) {
             String[] userIdSplit = PgpKeyHelper.splitUserId(userId);
 

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/adapter/SelectKeyCursorAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012-2013 Dominik Schürmann <dominik@dominikschuermann.de>
+ * Copyright (C) 2012-2014 Dominik Schürmann <dominik@dominikschuermann.de>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -40,6 +40,11 @@ public class SelectKeyCursorAdapter extends CursorAdapter {
     private LayoutInflater mInflater;
     private ListView mListView;
 
+    private int mIndexUserId;
+    private int mIndexMasterKeyId;
+    private int mIndexProjectionValid;
+    private int mIndexProjectionAvailable;
+
     public final static String PROJECTION_ROW_AVAILABLE = "available";
     public final static String PROJECTION_ROW_VALID = "valid";
 
@@ -50,21 +55,45 @@ public class SelectKeyCursorAdapter extends CursorAdapter {
         mInflater = LayoutInflater.from(context);
         mListView = listView;
         mKeyType = keyType;
+
+        initIndex(c);
+    }
+
+    @Override
+    public Cursor swapCursor(Cursor newCursor) {
+        initIndex(newCursor);
+
+        return super.swapCursor(newCursor);
+    }
+
+    /**
+     * Get column indexes for performance reasons just once in constructor and swapCursor. For a
+     * performance comparison see http://stackoverflow.com/a/17999582
+     * 
+     * @param cursor
+     */
+    private void initIndex(Cursor cursor) {
+        if (cursor != null) {
+            mIndexUserId = cursor.getColumnIndexOrThrow(UserIds.USER_ID);
+            mIndexMasterKeyId = cursor.getColumnIndexOrThrow(KeyRings.MASTER_KEY_ID);
+            mIndexProjectionValid = cursor.getColumnIndexOrThrow(PROJECTION_ROW_VALID);
+            mIndexProjectionAvailable = cursor.getColumnIndexOrThrow(PROJECTION_ROW_AVAILABLE);
+        }
     }
 
     public String getUserId(int position) {
         mCursor.moveToPosition(position);
-        return mCursor.getString(mCursor.getColumnIndex(UserIds.USER_ID));
+        return mCursor.getString(mIndexUserId);
     }
 
     public long getMasterKeyId(int position) {
         mCursor.moveToPosition(position);
-        return mCursor.getLong(mCursor.getColumnIndex(KeyRings.MASTER_KEY_ID));
+        return mCursor.getLong(mIndexMasterKeyId);
     }
 
     @Override
     public void bindView(View view, Context context, Cursor cursor) {
-        boolean valid = cursor.getInt(cursor.getColumnIndex(PROJECTION_ROW_VALID)) > 0;
+        boolean valid = cursor.getInt(mIndexProjectionValid) > 0;
 
         TextView mainUserId = (TextView) view.findViewById(R.id.mainUserId);
         mainUserId.setText(R.string.unknown_user_id);
@@ -75,7 +104,7 @@ public class SelectKeyCursorAdapter extends CursorAdapter {
         TextView status = (TextView) view.findViewById(R.id.status);
         status.setText(R.string.unknown_status);
 
-        String userId = cursor.getString(cursor.getColumnIndex(UserIds.USER_ID));
+        String userId = cursor.getString(mIndexUserId);
         if (userId != null) {
             String[] userIdSplit = PgpKeyHelper.splitUserId(userId);
 
@@ -85,7 +114,7 @@ public class SelectKeyCursorAdapter extends CursorAdapter {
             mainUserId.setText(userIdSplit[0]);
         }
 
-        long masterKeyId = cursor.getLong(cursor.getColumnIndex(KeyRings.MASTER_KEY_ID));
+        long masterKeyId = cursor.getLong(mIndexMasterKeyId);
         keyId.setText(PgpKeyHelper.convertKeyIdToHex(masterKeyId));
 
         if (mainUserIdRest.getText().length() == 0) {
@@ -99,7 +128,7 @@ public class SelectKeyCursorAdapter extends CursorAdapter {
                 status.setText(R.string.can_sign);
             }
         } else {
-            if (cursor.getInt(cursor.getColumnIndex(PROJECTION_ROW_AVAILABLE)) > 0) {
+            if (cursor.getInt(mIndexProjectionAvailable) > 0) {
                 // has some CAN_ENCRYPT keys, but col(ROW_VALID) = 0, so must be revoked or
                 // expired
                 status.setText(R.string.expired);

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/adapter/ViewKeyKeysAdapter.java

@@ -33,19 +33,52 @@ import android.widget.TextView;
 public class ViewKeyKeysAdapter extends CursorAdapter {
     private LayoutInflater mInflater;
 
+    private int mIndexKeyId;
+    private int mIndexAlgorithm;
+    private int mIndexKeySize;
+    private int mIndexIsMasterKey;
+    private int mIndexCanCertify;
+    private int mIndexCanEncrypt;
+    private int mIndexCanSign;
+
     public ViewKeyKeysAdapter(Context context, Cursor c, int flags) {
         super(context, c, flags);
 
         mInflater = LayoutInflater.from(context);
+
+        initIndex(c);
+    }
+
+    @Override
+    public Cursor swapCursor(Cursor newCursor) {
+        initIndex(newCursor);
+
+        return super.swapCursor(newCursor);
+    }
+
+    /**
+     * Get column indexes for performance reasons just once in constructor and swapCursor. For a
+     * performance comparison see http://stackoverflow.com/a/17999582
+     * 
+     * @param cursor
+     */
+    private void initIndex(Cursor cursor) {
+        if (cursor != null) {
+            mIndexKeyId = cursor.getColumnIndexOrThrow(Keys.KEY_ID);
+            mIndexAlgorithm = cursor.getColumnIndexOrThrow(Keys.ALGORITHM);
+            mIndexKeySize = cursor.getColumnIndexOrThrow(Keys.KEY_SIZE);
+            mIndexIsMasterKey = cursor.getColumnIndexOrThrow(Keys.IS_MASTER_KEY);
+            mIndexCanCertify = cursor.getColumnIndexOrThrow(Keys.CAN_CERTIFY);
+            mIndexCanEncrypt = cursor.getColumnIndexOrThrow(Keys.CAN_ENCRYPT);
+            mIndexCanSign = cursor.getColumnIndexOrThrow(Keys.CAN_SIGN);
+        }
     }
 
     @Override
     public void bindView(View view, Context context, Cursor cursor) {
-        String keyIdStr = PgpKeyHelper.convertKeyIdToHex(cursor.getLong(cursor
+        String keyIdStr = "0x" + PgpKeyHelper.convertKeyIdToHex(cursor.getLong(mIndexKeyId));
-                .getColumnIndex(Keys.KEY_ID)));
+        String algorithmStr = PgpKeyHelper.getAlgorithmInfo(cursor.getInt(mIndexAlgorithm),
-        String algorithmStr = PgpKeyHelper.getAlgorithmInfo(
+                cursor.getInt(mIndexKeySize));
-                cursor.getInt(cursor.getColumnIndex(Keys.ALGORITHM)),
-                cursor.getInt(cursor.getColumnIndex(Keys.KEY_SIZE)));
 
         TextView keyId = (TextView) view.findViewById(R.id.keyId);
         keyId.setText(keyIdStr);
@@ -54,28 +87,28 @@ public class ViewKeyKeysAdapter extends CursorAdapter {
         keyDetails.setText("(" + algorithmStr + ")");
 
         ImageView masterKeyIcon = (ImageView) view.findViewById(R.id.ic_masterKey);
-        if (cursor.getInt(cursor.getColumnIndex(Keys.IS_MASTER_KEY)) != 1) {
+        if (cursor.getInt(mIndexIsMasterKey) != 1) {
             masterKeyIcon.setVisibility(View.INVISIBLE);
         } else {
             masterKeyIcon.setVisibility(View.VISIBLE);
         }
 
         ImageView certifyIcon = (ImageView) view.findViewById(R.id.ic_certifyKey);
-        if (cursor.getInt(cursor.getColumnIndex(Keys.CAN_CERTIFY)) != 1) {
+        if (cursor.getInt(mIndexCanCertify) != 1) {
             certifyIcon.setVisibility(View.GONE);
         } else {
             certifyIcon.setVisibility(View.VISIBLE);
         }
 
         ImageView encryptIcon = (ImageView) view.findViewById(R.id.ic_encryptKey);
-        if (cursor.getInt(cursor.getColumnIndex(Keys.CAN_ENCRYPT)) != 1) {
+        if (cursor.getInt(mIndexCanEncrypt) != 1) {
             encryptIcon.setVisibility(View.GONE);
         } else {
             encryptIcon.setVisibility(View.VISIBLE);
         }
 
         ImageView signIcon = (ImageView) view.findViewById(R.id.ic_signKey);
-        if (cursor.getInt(cursor.getColumnIndex(Keys.CAN_SIGN)) != 1) {
+        if (cursor.getInt(mIndexCanSign) != 1) {
             signIcon.setVisibility(View.GONE);
         } else {
             signIcon.setVisibility(View.VISIBLE);

OpenPGP-Keychain/src/org/sufficientlysecure/keychain/ui/adapter/ViewKeyUserIdsAdapter.java

@@ -31,17 +31,38 @@ import android.widget.TextView;
 public class ViewKeyUserIdsAdapter extends CursorAdapter {
     private LayoutInflater mInflater;
 
+    private int mIndexUserId;
+
     public ViewKeyUserIdsAdapter(Context context, Cursor c, int flags) {
         super(context, c, flags);
 
         mInflater = LayoutInflater.from(context);
+
+        initIndex(c);
+    }
+
+    @Override
+    public Cursor swapCursor(Cursor newCursor) {
+        initIndex(newCursor);
+
+        return super.swapCursor(newCursor);
+    }
+
+    /**
+     * Get column indexes for performance reasons just once in constructor and swapCursor. For a
+     * performance comparison see http://stackoverflow.com/a/17999582
+     * 
+     * @param cursor
+     */
+    private void initIndex(Cursor cursor) {
+        if (cursor != null) {
+            mIndexUserId = cursor.getColumnIndexOrThrow(UserIds.USER_ID);
+        }
     }
 
     @Override
     public void bindView(View view, Context context, Cursor cursor) {
-        int userIdIndex = cursor.getColumnIndex(UserIds.USER_ID);
+        String userIdStr = cursor.getString(mIndexUserId);
-
-        String userIdStr = cursor.getString(userIdIndex);
 
         TextView userId = (TextView) view.findViewById(R.id.userId);
         userId.setText(userIdStr);