Fix bluetooth settings force close

This CL include following change:

- Add null check of cacedBluetoothDevice, cachedBluetooth could be null
  if the input BluetoothDevice can't found in
  CachedBluetoothDeviceManager.
- Move addPreference() and removePreference() to update() method,
  because update() will be called to update UI when recevice Bluetooth
  device change event.
- Add test case to test CachedBluetoothDevice null check.

Bug: 149068434
Test: make -j42 RunSettingsRoboTests
Change-Id: I90016bf1175925821b0d9b634c62cf796289a734

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

@@ -20,6 +20,7 @@ import android.bluetooth.BluetoothDevice;
 import android.content.Context;
 import android.util.Log;
 
+import androidx.annotation.VisibleForTesting;
 import androidx.preference.Preference;
 
 import com.android.settings.connecteddevice.DevicePreferenceCallback;
@@ -38,24 +39,25 @@ public class SavedBluetoothDeviceUpdater extends BluetoothDeviceUpdater
 
     private static final String PREF_KEY = "saved_bt";
 
+    @VisibleForTesting
+    BluetoothAdapter mBluetoothAdapter;
+
     public SavedBluetoothDeviceUpdater(Context context, DashboardFragment fragment,
             DevicePreferenceCallback devicePreferenceCallback) {
         super(context, fragment, devicePreferenceCallback);
+
+        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
     }
 
     @Override
     public void forceUpdate() {
-        if (BluetoothAdapter.getDefaultAdapter().isEnabled()) {
+        if (mBluetoothAdapter.isEnabled()) {
             final CachedBluetoothDeviceManager cachedManager =
                     mLocalManager.getCachedDeviceManager();
-            for (BluetoothDevice device
-                    : BluetoothAdapter.getDefaultAdapter().getMostRecentlyConnectedDevices()) {
+            for (BluetoothDevice device : mBluetoothAdapter.getMostRecentlyConnectedDevices()) {
                 final CachedBluetoothDevice cachedDevice = cachedManager.findDevice(device);
-                if (isFilterMatched(cachedDevice)) {
-                    // Add the preference if it is new one
-                    addPreference(cachedDevice, BluetoothDevicePreference.SortType.TYPE_NO_SORT);
-                } else {
-                    removePreference(cachedDevice);
+                if (cachedDevice != null) {
+                    update(cachedDevice);
                 }
             }
         } else {
@@ -63,6 +65,16 @@ public class SavedBluetoothDeviceUpdater extends BluetoothDeviceUpdater
         }
     }
 
+    @Override
+    public void update(CachedBluetoothDevice cachedDevice) {
+        if (isFilterMatched(cachedDevice)) {
+            // Add the preference if it is new one
+            addPreference(cachedDevice, BluetoothDevicePreference.SortType.TYPE_NO_SORT);
+        } else {
+            removePreference(cachedDevice);
+        }
+    }
+
     @Override
     public boolean isFilterMatched(CachedBluetoothDevice cachedDevice) {
         final BluetoothDevice device = cachedDevice.getDevice();