Fix media output slice is empty even BT device is paired

Return the empty ListBuilder instead of return null in
getSlice().

Bug: 131140677
Test: make -j42 RunSettingsRobotests
Change-Id: I2b1a4bc0c6d2017ec85b2e9f8a5bfc08a0eba1b5

src/com/android/settings/media/MediaOutputSlice.java

@@ -70,21 +70,27 @@ public class MediaOutputSlice implements CustomSliceable {
 
     @Override
     public Slice getSlice() {
+        // Reload theme for switching dark mode on/off
+        mContext.getTheme().applyStyle(R.style.Theme_Settings_Home, true /* force */);
+
+        final ListBuilder listBuilder = new ListBuilder(mContext, getUri(), ListBuilder.INFINITY)
+                .setAccentColor(COLOR_NOT_TINTED);
+
         final BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
         if (!adapter.isEnabled()) {
             Log.d(TAG, "getSlice() Bluetooth is off");
-            return null;
+            return listBuilder.build();
         }
 
         if (getWorker() == null) {
             Log.d(TAG, "getSlice() Can not get worker through uri!");
-            return null;
+            return listBuilder.build();
         }
 
         final List<MediaDevice> devices = getMediaDevices();
 
         final MediaDevice connectedDevice = getWorker().getCurrentConnectedMediaDevice();
-        final ListBuilder listBuilder = buildActiveDeviceHeader(connectedDevice);
+        listBuilder.addRow(getActiveDeviceHeaderRow(connectedDevice));
 
         for (MediaDevice device : devices) {
             if (!TextUtils.equals(connectedDevice.getId(), device.getId())) {
@@ -95,7 +101,7 @@ public class MediaOutputSlice implements CustomSliceable {
         return listBuilder.build();
     }
 
-    private ListBuilder buildActiveDeviceHeader(MediaDevice device) {
+    private ListBuilder.RowBuilder getActiveDeviceHeaderRow(MediaDevice device) {
         final String title = device.getName();
         final IconCompat icon = getDeviceIconCompat(device);
 
@@ -104,16 +110,13 @@ public class MediaOutputSlice implements CustomSliceable {
         final SliceAction primarySliceAction = SliceAction.createDeeplink(broadcastAction, icon,
                 ListBuilder.ICON_IMAGE, title);
 
-        final ListBuilder listBuilder = new ListBuilder(mContext, MEDIA_OUTPUT_SLICE_URI,
-                ListBuilder.INFINITY)
-                .setAccentColor(COLOR_NOT_TINTED)
-                .addRow(new ListBuilder.RowBuilder()
-                        .setTitleItem(icon, ListBuilder.ICON_IMAGE)
-                        .setTitle(title)
-                        .setSubtitle(device.getSummary())
-                        .setPrimaryAction(primarySliceAction));
+        final ListBuilder.RowBuilder rowBuilder = new ListBuilder.RowBuilder()
+                .setTitleItem(icon, ListBuilder.ICON_IMAGE)
+                .setTitle(title)
+                .setSubtitle(device.getSummary())
+                .setPrimaryAction(primarySliceAction);
 
-        return listBuilder;
+        return rowBuilder;
     }
 
     private IconCompat getDeviceIconCompat(MediaDevice device) {

tests/robotests/src/com/android/settings/media/MediaOutputSliceTest.java

@@ -17,6 +17,9 @@
 
 package com.android.settings.media;
 
+import static android.app.slice.Slice.HINT_LIST_ITEM;
+import static android.app.slice.SliceItem.FORMAT_SLICE;
+
 import static com.android.settings.slices.CustomSliceRegistry.MEDIA_OUTPUT_SLICE_URI;
 
 import static com.google.common.truth.Truth.assertThat;
@@ -36,6 +39,7 @@ import androidx.slice.Slice;
 import androidx.slice.SliceMetadata;
 import androidx.slice.SliceProvider;
 import androidx.slice.core.SliceAction;
+import androidx.slice.core.SliceQuery;
 import androidx.slice.widget.SliceLiveData;
 
 import com.android.settings.testutils.shadow.ShadowBluetoothAdapter;
@@ -97,10 +101,27 @@ public class MediaOutputSliceTest {
     }
 
     @Test
-    public void getSlice_workerIsNull_shouldNotCrash() {
+    public void getSlice_workerIsNull_shouldReturnZeroRow() {
         mMediaOutputSlice.init(TEST_PACKAGE_NAME, null);
 
-        mMediaOutputSlice.getSlice();
+        final Slice slice = mMediaOutputSlice.getSlice();
+
+        final int rows = SliceQuery.findAll(slice, FORMAT_SLICE, HINT_LIST_ITEM,
+                null /* nonHints */).size();
+
+        assertThat(rows).isEqualTo(0);
+    }
+
+    @Test
+    public void getSlice_bluetoothIsDisable_shouldReturnZeroRow() {
+        mShadowBluetoothAdapter.setEnabled(false);
+
+        final Slice slice = mMediaOutputSlice.getSlice();
+
+        final int rows = SliceQuery.findAll(slice, FORMAT_SLICE, HINT_LIST_ITEM,
+                null /* nonHints */).size();
+
+        assertThat(rows).isEqualTo(0);
     }
 
     @Test