Create a staleScanResults bit.

This bit is set to true during stop tracking and will not change until
fresh scan results come in. This bit is used to prevent
onAccessPointsChanged callbacks from being invoked until other new scan
results are processed.

This is necessary to fix a UI issue in WifiSettings during app
resumption where sticky broadcasts from other intents come in before
a new scan result is available, causing us to clear out all shown APs
since the ScanResults are stale and thus removed from the picker.

Bug: b/38212080
Test: runtest --path
frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java

Change-Id: I2f1fd84d1ab3461d9c8eac9511b90ba7533879c1

2 files changed, 48 insertions, 2 deletions

diff --git a/packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java b/packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java
index 40a59cf1ab82..fcc9090fc2f3 100644
--- a/packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java
+++ b/packages/SettingsLib/src/com/android/settingslib/wifi/WifiTracker.java
@@ -142,6 +142,7 @@ public class WifiTracker {
 
     @VisibleForTesting
     Scanner mScanner;
+    private boolean mStaleScanResults = false;
 
     public WifiTracker(Context context, WifiListener wifiListener,
             boolean includeSaved, boolean includeScans) {
@@ -330,7 +331,11 @@ public class WifiTracker {
      * Stop tracking wifi networks and scores.
      *
      * <p>This should always be called when done with a WifiTracker (if startTracking was called) to
-     * ensure proper cleanup and prevent any further callbacks from occuring.
+     * ensure proper cleanup and prevent any further callbacks from occurring.
+     *
+     * <p>Calling this method will set the {@link #mStaleScanResults} bit, which prevents
+     * {@link WifiListener#onAccessPointsChanged()} callbacks from being invoked (until the bit
+     * is unset on the next SCAN_RESULTS_AVAILABLE_ACTION).
      */
     @MainThread
     public void stopTracking() {
@@ -346,6 +351,7 @@ public class WifiTracker {
             mWorkHandler.removePendingMessages();
             mMainHandler.removePendingMessages();
         }
+        mStaleScanResults = true;
     }
 
     private void unregisterAndClearScoreCache() {
@@ -712,6 +718,11 @@ public class WifiTracker {
         @Override
         public void onReceive(Context context, Intent intent) {
             String action = intent.getAction();
+
+            if (WifiManager.SCAN_RESULTS_AVAILABLE_ACTION.equals(action)) {
+                mStaleScanResults = false;
+            }
+
             if (WifiManager.WIFI_STATE_CHANGED_ACTION.equals(action)) {
                 updateWifiState(intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE,
                         WifiManager.WIFI_STATE_UNKNOWN));
@@ -822,7 +833,9 @@ public class WifiTracker {
 
             switch (msg.what) {
                 case MSG_UPDATE_ACCESS_POINTS:
-                    updateAccessPointsLocked();
+                    if (!mStaleScanResults) {
+                        updateAccessPointsLocked();
+                    }
                     break;
                 case MSG_UPDATE_NETWORK_INFO:
                     updateNetworkInfo((NetworkInfo) msg.obj);
diff --git a/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java b/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java
index c52643243063..eb9a7f6d0843 100644
--- a/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java
+++ b/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java
@@ -28,6 +28,7 @@ import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -748,4 +749,36 @@ public class WifiTrackerTest {
 
         verifyNoMoreInteractions(mockWifiListener);
     }
+
+    @Test
+    public void stopTrackingShouldSetStaleBitWhichPreventsCallbacksUntilNextScanResult()
+            throws Exception {
+        WifiTracker tracker = createMockedWifiTracker();
+        startTracking(tracker);
+        tracker.stopTracking();
+
+        CountDownLatch latch1 = new CountDownLatch(1);
+        tracker.mMainHandler.post(() -> {
+                latch1.countDown();
+        });
+        assertTrue("Latch 1 timed out", latch1.await(LATCH_TIMEOUT, TimeUnit.MILLISECONDS));
+
+        startTracking(tracker);
+
+        tracker.mReceiver.onReceive(mContext, new Intent(WifiManager.WIFI_STATE_CHANGED_ACTION));
+        tracker.mReceiver.onReceive(
+                mContext, new Intent(WifiManager.CONFIGURED_NETWORKS_CHANGED_ACTION));
+        tracker.mReceiver.onReceive(
+                mContext, new Intent(WifiManager.LINK_CONFIGURATION_CHANGED_ACTION));
+
+        CountDownLatch latch2 = new CountDownLatch(1);
+        tracker.mMainHandler.post(() -> {
+            latch2.countDown();
+        });
+        assertTrue("Latch 2 timed out", latch2.await(LATCH_TIMEOUT, TimeUnit.MILLISECONDS));
+
+        verify(mockWifiListener, never()).onAccessPointsChanged();
+
+        sendScanResultsAndProcess(tracker); // verifies onAccessPointsChanged is invoked
+    }
 }