Prevent NPE's in calls to database utility methods

* Before the Email/Exchange split, EmailProvider was guaranteed not to return a null
  cursor; this is no longer true
* We now throw a new RuntimeException (ProviderUnavailableException) when calling
  commonly-used utility methods (e.g. restoreXWithId) and the cursor as returned from
  EmailProvider is null (which implies that the provider isn't available).

Change-Id: I152d13bff0129c23586cd570d23c87d69cfce372

emailcommon/src/com/android/emailcommon/provider/EmailContent.java

@@ -138,7 +138,7 @@ public abstract class EmailContent {
             Class<T> klass, Uri contentUri, String[] contentProjection, long id) {
         Uri u = ContentUris.withAppendedId(contentUri, id);
         Cursor c = context.getContentResolver().query(u, contentProjection, null, null, null);
-
+        if (c == null) throw new ProviderUnavailableException();
         try {
             if (c.moveToFirst()) {
                 return (T)getContent(c, klass);
@@ -322,6 +322,11 @@ public abstract class EmailContent {
             return values;
         }
 
+        /**
+         * Given a cursor, restore a Body from it
+         * @param cursor a cursor which must NOT be null
+         * @return the Body as restored from the cursor
+         */
         private static Body restoreBodyWithCursor(Cursor cursor) {
             try {
                 if (cursor.moveToFirst()) {
@@ -338,6 +343,7 @@ public abstract class EmailContent {
             Uri u = ContentUris.withAppendedId(Body.CONTENT_URI, id);
             Cursor c = context.getContentResolver().query(u, Body.CONTENT_PROJECTION,
                     null, null, null);
+            if (c == null) throw new ProviderUnavailableException();
             return restoreBodyWithCursor(c);
         }
 
@@ -345,6 +351,7 @@ public abstract class EmailContent {
             Cursor c = context.getContentResolver().query(Body.CONTENT_URI,
                     Body.CONTENT_PROJECTION, Body.MESSAGE_KEY + "=?",
                     new String[] {Long.toString(messageId)}, null);
+            if (c == null) throw new ProviderUnavailableException();
             return restoreBodyWithCursor(c);
         }
 
@@ -387,6 +394,7 @@ public abstract class EmailContent {
                 String[] projection) {
             Cursor c = context.getContentResolver().query(Body.CONTENT_URI, projection,
                     Body.MESSAGE_KEY + "=?", new String[] {Long.toString(messageId)}, null);
+            if (c == null) throw new ProviderUnavailableException();
             try {
                 if (c.moveToFirst()) {
                     return c.getString(COMMON_PROJECTION_COLUMN_TEXT);
@@ -2429,8 +2437,7 @@ public abstract class EmailContent {
                     Mailbox.PATH_AND_ACCOUNT_SELECTION,
                     new String[] { path, Long.toString(accountId) },
                     null);
-// TODO for mblank; uncomment when you submit CL Iab059f9a68eecd797914a6229f1ff9c03d0f0800
-//            if (c == null) throw new ProviderUnavailableException();
+            if (c == null) throw new ProviderUnavailableException();
             try {
                 Mailbox mailbox = null;
                 if (c.moveToFirst()) {

emailcommon/src/com/android/emailcommon/provider/ProviderUnavailableException.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.emailcommon.provider;
+
+public class ProviderUnavailableException extends RuntimeException {
+    private static final long serialVersionUID = 1L;
+}

emailcommon/src/com/android/emailcommon/utility/Utility.java

@@ -28,6 +28,7 @@ import com.android.emailcommon.provider.EmailContent.Mailbox;
 import com.android.emailcommon.provider.EmailContent.MailboxColumns;
 import com.android.emailcommon.provider.EmailContent.Message;
 import com.android.emailcommon.provider.EmailContent.MessageColumns;
+import com.android.emailcommon.provider.ProviderUnavailableException;
 
 import android.app.Activity;
 import android.content.ContentResolver;
@@ -42,8 +43,6 @@ import android.os.AsyncTask;
 import android.os.Environment;
 import android.os.Handler;
 import android.os.Looper;
-import android.os.Parcel;
-import android.os.Parcelable;
 import android.os.StrictMode;
 import android.provider.OpenableColumns;
 import android.text.Spannable;
@@ -53,7 +52,6 @@ import android.text.TextUtils;
 import android.text.style.StyleSpan;
 import android.util.Base64;
 import android.util.Log;
-import android.widget.AbsListView;
 import android.widget.ListView;
 import android.widget.TextView;
 import android.widget.Toast;
@@ -325,6 +323,7 @@ public class Utility {
         ContentResolver resolver = context.getContentResolver();
         Cursor c = resolver.query(HostAuth.CONTENT_URI, HostAuth.ID_PROJECTION,
                 HOSTAUTH_WHERE_CREDENTIALS, new String[] { hostName, userLogin }, null);
+        if (c == null) throw new ProviderUnavailableException();
         try {
             while (c.moveToNext()) {
                 long hostAuthId = c.getLong(HostAuth.ID_PROJECTION_COLUMN);