Fix crash on Wi-Fi Slice when it's continuously pinned and unpinned

It's because WifiTracker's initialization and onStop is on different
thread. Fine tune the thread logic in SliceBackgroundWorker.

Fixes: 118165942
Test: manual
Change-Id: Icc86b5df7ec3c6fd0e4a79a62ea0c84465e9528d

src/com/android/settings/slices/SettingsSliceProvider.java

@@ -52,6 +52,7 @@ import com.android.settings.wifi.calling.WifiCallingSliceHelper;
 import com.android.settingslib.SliceBroadcastRelay;
 import com.android.settingslib.utils.ThreadUtils;
 
+import java.io.IOException;
 import java.net.URISyntaxException;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -134,6 +135,7 @@ public class SettingsSliceProvider extends SliceProvider {
     final Set<Uri> mRegisteredUris = new ArraySet<>();
 
     final Map<Uri, SliceBackgroundWorker> mWorkerMap = new ArrayMap<>();
+    final Set<SliceBackgroundWorker> mLiveWorkers = new ArraySet<>();
 
     public SettingsSliceProvider() {
         super(READ_SEARCH_INDEXABLES);
@@ -169,7 +171,9 @@ public class SettingsSliceProvider extends SliceProvider {
             if (filter != null) {
                 registerIntentToUri(filter, sliceUri);
             }
-            startBackgroundWorker(sliceable);
+            ThreadUtils.postOnMainThread(() -> {
+                startBackgroundWorker(sliceable);
+            });
             return;
         }
 
@@ -198,7 +202,9 @@ public class SettingsSliceProvider extends SliceProvider {
             SliceBroadcastRelay.unregisterReceivers(getContext(), sliceUri);
             mRegisteredUris.remove(sliceUri);
         }
-        stopBackgroundWorker(sliceUri);
+        ThreadUtils.postOnMainThread(() -> {
+            stopBackgroundWorker(sliceUri);
+        });
         mSliceDataCache.remove(sliceUri);
     }
 
@@ -365,12 +371,15 @@ public class SettingsSliceProvider extends SliceProvider {
         }
 
         final Uri uri = sliceable.getUri();
-        Log.d(TAG, "Starting background worker for: " + uri);
         if (mWorkerMap.containsKey(uri)) {
             return;
         }
 
+        Log.d(TAG, "Starting background worker for: " + uri);
         mWorkerMap.put(uri, worker);
+        if (!mLiveWorkers.contains(worker)) {
+            mLiveWorkers.add(worker);
+        }
         worker.onSlicePinned();
     }
 
@@ -383,6 +392,20 @@ public class SettingsSliceProvider extends SliceProvider {
         }
     }
 
+    @Override
+    public void shutdown() {
+        for (SliceBackgroundWorker worker : mLiveWorkers) {
+            ThreadUtils.postOnMainThread(() -> {
+                try {
+                    worker.close();
+                } catch (IOException e) {
+                    Log.w(TAG, "Exception when shutting down worker", e);
+                }
+            });
+        }
+        mLiveWorkers.clear();
+    }
+
     private List<Uri> buildUrisFromKeys(List<String> keys, String authority) {
         final List<Uri> descendants = new ArrayList<>();
 

src/com/android/settings/slices/SliceBackgroundWorker.java

@@ -16,9 +16,11 @@
 
 package com.android.settings.slices;
 
+import android.annotation.MainThread;
 import android.content.ContentResolver;
 import android.net.Uri;
 
+import java.io.Closeable;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -32,7 +34,7 @@ import java.util.List;
  * {@link SliceBackgroundWorker} caches the results, uses the cache to compare if there is any data
  * changed, and then notifies the Slice {@link Uri} to update.
  */
-public abstract class SliceBackgroundWorker<E> {
+public abstract class SliceBackgroundWorker<E> implements Closeable {
 
     private final ContentResolver mContentResolver;
     private final Uri mUri;
@@ -48,12 +50,14 @@ public abstract class SliceBackgroundWorker<E> {
      * Called when the Slice is pinned. This is the place to register callbacks or initialize scan
      * tasks.
      */
+    @MainThread
     protected abstract void onSlicePinned();
 
     /**
      * Called when the Slice is unpinned. This is the place to unregister callbacks or perform any
      * final cleanup.
      */
+    @MainThread
     protected abstract void onSliceUnpinned();
 
     /**