Reset stopwatches with bad data on first load

Bug: 34742962
Test: Manually create

There was a time when it was possible for a stopwatch with
negative elapsed time could be recorded. This bad data can
cause formatting exceptions in the new code. To avoid these
exceptions, the stopwatch is reset if it loaded in this bad state.

Change-Id: I5cdd287c96bd87a82876b7a8cb3643313045f667

2 files changed, 16 insertions, 5 deletions

diff --git a/src/com/android/deskclock/data/StopwatchDAO.java b/src/com/android/deskclock/data/StopwatchDAO.java
index 823ab63fd..541390148 100644
--- a/src/com/android/deskclock/data/StopwatchDAO.java
+++ b/src/com/android/deskclock/data/StopwatchDAO.java
@@ -61,7 +61,14 @@ final class StopwatchDAO {
         final long lastStartTime = prefs.getLong(LAST_START_TIME, Stopwatch.UNUSED);
         final long lastWallClockTime = prefs.getLong(LAST_WALL_CLOCK_TIME, Stopwatch.UNUSED);
         final long accumulatedTime = prefs.getLong(ACCUMULATED_TIME, 0);
-        return new Stopwatch(state, lastStartTime, lastWallClockTime, accumulatedTime);
+        Stopwatch s = new Stopwatch(state, lastStartTime, lastWallClockTime, accumulatedTime);
+
+        // If the stopwatch reports an illegal (negative) amount of time, remove the bad data.
+        if (s.getTotalTime() < 0) {
+            s = s.reset();
+            setStopwatch(prefs, s);
+        }
+        return s;
     }
 
     /**
diff --git a/src/com/android/deskclock/data/Timer.java b/src/com/android/deskclock/data/Timer.java
index 816d58786..71716a375 100644
--- a/src/com/android/deskclock/data/Timer.java
+++ b/src/com/android/deskclock/data/Timer.java
@@ -139,14 +139,18 @@ public final class Timer {
 
     /**
      * @return the total amount of time remaining up to this moment; expired and missed timers will
-     * return a negative amount
+     *      return a negative amount
      */
     public long getRemainingTime() {
-        if (mState == RUNNING || mState == EXPIRED || mState == MISSED) {
-            return mRemainingTime - (now() - mLastStartTime);
+        if (mState == PAUSED || mState == RESET) {
+            return mRemainingTime;
         }
 
-        return mRemainingTime;
+        // In practice, "now" can be any value due to device reboots. When the real-time clock
+        // is reset, there is no more guarantee that "now" falls after the last start time. To
+        // ensure the timer is monotonically decreasing, normalize negative time segments to 0,
+        final long timeSinceStart = now() - mLastStartTime;
+        return mRemainingTime - Math.max(0, timeSinceStart);
     }
 
     /**