configure reset_account menu item from fragment, thus getting rid of one expensive db call

Author: mtotschnig

src/org/totschnig/myexpenses/activity/MyExpenses.java

@@ -259,8 +259,6 @@ public boolean onPrepareOptionsMenu(Menu menu) {
     super.onPrepareOptionsMenu(menu);
     //I would prefer to use setEnabled, but the disabled state unfortunately is not visually reflected
     //in the actionbar
-    menu.findItem(R.id.RESET_ACCOUNT_COMMAND)
-      .setVisible(mCurrentAccount.getSize() > 0);
     menu.findItem(R.id.INSERT_TRANSFER_COMMAND)
       .setVisible(Account.countPerCurrency(mCurrentAccount.currency) > 1);
     menu.findItem(R.id.NEW_FROM_TEMPLATE_COMMAND)

src/org/totschnig/myexpenses/fragment/TransactionList.java

@@ -14,6 +14,7 @@
 
 import com.actionbarsherlock.app.SherlockFragment;
 import com.actionbarsherlock.app.SherlockFragmentActivity;
+import com.actionbarsherlock.view.Menu;
 
 import android.content.ContentResolver;
 import android.content.Intent;
@@ -49,6 +50,7 @@ public class TransactionList extends SherlockFragment implements LoaderManager.L
   private Account mAccount;
   private TextView balanceTv;
   private View bottomLine;
+  private boolean hasItems;
 
   public static TransactionList newInstance(long accountId) {
 
@@ -61,6 +63,7 @@ public static TransactionList newInstance(long accountId) {
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
+      setHasOptionsMenu(true);
       accountId = getArguments().getLong("account_id");
       mAccount = Account.getInstanceFromDb(getArguments().getLong("account_id"));
       tObserver = new TransactionsObserver(new Handler());
@@ -87,6 +90,11 @@ public void onDestroy() {
         // Do Nothing.  Observer has already been unregistered.
     }
   }
+  @Override
+  public void onPrepareOptionsMenu(Menu menu) {
+    if (isVisible())
+      menu.findItem(R.id.RESET_ACCOUNT_COMMAND).setVisible(hasItems);
+  }
 
   @Override  
   public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
@@ -214,11 +222,17 @@ public Loader<Cursor> onCreateLoader(int arg0, Bundle arg1) {
   @Override
   public void onLoadFinished(Loader<Cursor> arg0, Cursor c) {
     mAdapter.swapCursor(c);
+    hasItems = c.getCount()>0;
+    if (isVisible())
+      getSherlockActivity().supportInvalidateOptionsMenu();
   }
 
   @Override
   public void onLoaderReset(Loader<Cursor> arg0) {
     mAdapter.swapCursor(null);
+    hasItems = false;
+    if (isVisible())
+      getSherlockActivity().supportInvalidateOptionsMenu();
   }
   class TransactionsObserver extends ContentObserver {
     public TransactionsObserver(Handler handler) {