Use FooterPreference in xml explicitly

- Removed the FooterPreferenceMixin from the BluetoothDetailsMacAddressController.
 - Added the common api addFooterPreference.

Fixes: 139104386
Test: manual test
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.bluetooth
Change-Id: Iab40fa4c5be674290b1dc6d372c84609ccc2ea49

src/com/android/settings/bluetooth/BluetoothDetailsMacAddressController.java

@@ -25,13 +25,13 @@ import com.android.settings.R;
 import com.android.settingslib.bluetooth.CachedBluetoothDevice;
 import com.android.settingslib.core.lifecycle.Lifecycle;
 import com.android.settingslib.widget.FooterPreference;
-import com.android.settingslib.widget.FooterPreferenceMixinCompat;
 
 /**
  * This class adds the device MAC address to a footer.
  */
 public class BluetoothDetailsMacAddressController extends BluetoothDetailsController {
-    FooterPreferenceMixinCompat mFooterPreferenceMixin;
+    public static final String KEY_DEVICE_DETAILS_FOOTER = "device_details_footer";
+
     FooterPreference mFooterPreference;
 
     public BluetoothDetailsMacAddressController(Context context,
@@ -39,12 +39,11 @@ public class BluetoothDetailsMacAddressController extends BluetoothDetailsContro
             CachedBluetoothDevice device,
             Lifecycle lifecycle) {
         super(context, fragment, device, lifecycle);
-        mFooterPreferenceMixin = new FooterPreferenceMixinCompat(fragment, lifecycle);
     }
 
     @Override
     protected void init(PreferenceScreen screen) {
-        mFooterPreference = mFooterPreferenceMixin.createFooterPreference();
+        mFooterPreference = screen.findPreference(KEY_DEVICE_DETAILS_FOOTER);
         mFooterPreference.setTitle(mContext.getString(
                 R.string.bluetooth_device_mac_address, mCachedDevice.getAddress()));
     }
@@ -57,9 +56,6 @@ public class BluetoothDetailsMacAddressController extends BluetoothDetailsContro
 
     @Override
     public String getPreferenceKey() {
-        if (mFooterPreference == null) {
-            return null;
-        }
-        return mFooterPreference.getKey();
+        return KEY_DEVICE_DETAILS_FOOTER;
     }
 }