Fix race condition in CarrierTextController

If WakefulnessLifcecycle dispatches to CarrierTextController after the
CarrierTextCallback has been cleared but the observer has not been
removed, there will be an NPE.

This change guards the callback against dispatching to a null object.

Test: build and unlock
Fixes: 142130321
Change-Id: I5da46a0d5c8308870f2b67ae4622daf8e2d53b2f

1 files changed, 4 insertions, 2 deletions

diff --git a/packages/SystemUI/src/com/android/keyguard/CarrierTextController.java b/packages/SystemUI/src/com/android/keyguard/CarrierTextController.java
index a97ec6442e14..ef9538dbef38 100644
--- a/packages/SystemUI/src/com/android/keyguard/CarrierTextController.java
+++ b/packages/SystemUI/src/com/android/keyguard/CarrierTextController.java
@@ -35,6 +35,7 @@ import android.telephony.TelephonyManager;
 import android.text.TextUtils;
 import android.util.Log;
 
+import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 
 import com.android.internal.telephony.IccCardConstants;
@@ -66,6 +67,7 @@ public class CarrierTextController {
     private WifiManager mWifiManager;
     private boolean[] mSimErrorState;
     private final int mSimSlotsNumber;
+    @Nullable // Check for nullability before dispatching
     private CarrierTextCallback mCarrierTextCallback;
     private Context mContext;
     private CharSequence mSeparator;
@@ -74,12 +76,12 @@ public class CarrierTextController {
             new WakefulnessLifecycle.Observer() {
                 @Override
                 public void onFinishedWakingUp() {
-                    mCarrierTextCallback.finishedWakingUp();
+                    if (mCarrierTextCallback != null) mCarrierTextCallback.finishedWakingUp();
                 }
 
                 @Override
                 public void onStartedGoingToSleep() {
-                    mCarrierTextCallback.startedGoingToSleep();
+                    if (mCarrierTextCallback != null) mCarrierTextCallback.startedGoingToSleep();
                 }
             };