Hide wifi card sometimes.

When there is a connected wifi, we now hide the wifi slice card.

However, if we initially shows this card but later wifi is connected
while the card is visible, we keep showing this card to avoid janky
animation. The card will be gone if user nagivates to a different UI and
comes back.

- Create a new slice ContextualWifiSlice for homepage use case, all
  special logic for homepage are added here.
- Change reference for WIFI_SLICE to CONTEXTUAL_WIFI_SLICE where make
  sense.

Change-Id: Ibd87f88058f357aabef0f7d68a5bf48350d75b06
Fixes: 121040746
Test: robotests

src/com/android/settings/wifi/slice/ContextualWifiSlice.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.wifi.slice;
+
+import android.content.Context;
+import android.net.Uri;
+import android.net.wifi.WifiSsid;
+import android.text.TextUtils;
+import android.util.Log;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.slice.Slice;
+
+import com.android.settings.slices.CustomSliceRegistry;
+import com.android.settings.slices.CustomSliceable;
+
+/**
+ * {@link CustomSliceable} for Wi-Fi, used by contextual homepage.
+ */
+public class ContextualWifiSlice extends WifiSlice {
+
+    private static final String TAG = "ContextualWifiSlice";
+    @VisibleForTesting
+    boolean mPreviouslyDisplayed;
+
+    public ContextualWifiSlice(Context context) {
+        super(context);
+    }
+
+    @Override
+    public Uri getUri() {
+        return CustomSliceRegistry.CONTEXTUAL_WIFI_SLICE_URI;
+    }
+
+    @Override
+    public Slice getSlice() {
+        if (!mPreviouslyDisplayed && !TextUtils.equals(getActiveSSID(), WifiSsid.NONE)) {
+            Log.d(TAG, "Wifi is connected, no point showing any suggestion.");
+            return null;
+        }
+        // Set mPreviouslyDisplayed to true - we will show *something* on the screen. So we should
+        // keep showing this card to keep UI stable, even if wifi connects to a network later.
+        mPreviouslyDisplayed = true;
+
+        return super.getSlice();
+    }
+}