From 8bb09238bb466feb7e9146ec9efd683684cfbf93 Mon Sep 17 00:00:00 2001
From: tom hsu <tomhsu@google.com>
Date: Tue, 13 Jun 2023 17:00:57 +0800
Subject: [PATCH] [Settings] Avoid NPE when user enter WifiCallingSettings back
 and forth

Bug: 277833102
Test: Manual test
Change-Id: Ifd3272ddf8b8a27fc7772d860653df2c33a3df7b
---
 .../calling/WifiCallingSettingsForSub.java    | 28 +++++--------------
 1 file changed, 7 insertions(+), 21 deletions(-)

diff --git a/src/com/android/settings/wifi/calling/WifiCallingSettingsForSub.java b/src/com/android/settings/wifi/calling/WifiCallingSettingsForSub.java
index 0c3d769f661..3890ddfcdde 100644
--- a/src/com/android/settings/wifi/calling/WifiCallingSettingsForSub.java
+++ b/src/com/android/settings/wifi/calling/WifiCallingSettingsForSub.java
@@ -94,7 +94,6 @@ public class WifiCallingSettingsForSub extends SettingsPreferenceFragment
     private ListWithEntrySummaryPreference mButtonWfcRoamingMode;
     private Preference mUpdateAddress;
 
-    private boolean mValidListener = false;
     private boolean mEditableWfcMode = true;
     private boolean mEditableWfcRoamingMode = true;
     private boolean mUseWfcHomeModeForRoaming = false;
@@ -104,7 +103,7 @@ public class WifiCallingSettingsForSub extends SettingsPreferenceFragment
     private ProvisioningManager mProvisioningManager;
     private TelephonyManager mTelephonyManager;
 
-    private final PhoneTelephonyCallback mTelephonyCallback = new PhoneTelephonyCallback();
+    private PhoneTelephonyCallback mTelephonyCallback;
 
     private class PhoneTelephonyCallback extends TelephonyCallback implements
             TelephonyCallback.CallStateListener {
@@ -418,27 +417,20 @@ public class WifiCallingSettingsForSub extends SettingsPreferenceFragment
     @Override
     public void onResume() {
         super.onResume();
-
         updateBody();
-
-        final Context context = getActivity();
-        if (queryImsState(mSubId).isWifiCallingSupported()) {
+        Context context = getActivity();
+        if (mTelephonyCallback == null && queryImsState(mSubId).isWifiCallingSupported()) {
+            mTelephonyCallback = new PhoneTelephonyCallback();
             getTelephonyManagerForSub(mSubId).registerTelephonyCallback(
                     context.getMainExecutor(), mTelephonyCallback);
-
             mSwitchBar.addOnSwitchChangeListener(this);
-
-            mValidListener = true;
         }
-
         context.registerReceiver(mIntentReceiver, mIntentFilter,
                 Context.RECEIVER_EXPORTED_UNAUDITED);
-
         final Intent intent = getActivity().getIntent();
         if (intent.getBooleanExtra(Phone.EXTRA_KEY_ALERT_SHOW, false)) {
             showAlert(intent);
         }
-
         // Register callback for provisioning changes.
         registerProvisioningChangedCallback();
     }
@@ -446,19 +438,13 @@ public class WifiCallingSettingsForSub extends SettingsPreferenceFragment
     @Override
     public void onPause() {
         super.onPause();
-
-        final Context context = getActivity();
-
-        if (mValidListener) {
-            mValidListener = false;
-
+        Context context = getActivity();
+        if (mTelephonyCallback != null) {
             getTelephonyManagerForSub(mSubId).unregisterTelephonyCallback(mTelephonyCallback);
-
+            mTelephonyCallback = null;
             mSwitchBar.removeOnSwitchChangeListener(this);
         }
-
         context.unregisterReceiver(mIntentReceiver);
-
         // Remove callback for provisioning changes.
         unregisterProvisioningChangedCallback();
     }