BT device picker: don't rescan after rotating the device

The Bluetooth device picker was restarting the device scan after
the screen is rotated. Fix this by only starting the scan when the
savedInstanceState Bundle passed to onCreate() is null.

Also removes "No Bluetooth devices were found nearby" from list if
the user switches to a different app and then switches back to
the device picker.

Bug: 5249380
Change-Id: I8959c850649eb713fb930ee0a8a7bcb73ca7c1aa

src/com/android/settings/ProgressCategory.java

@@ -45,13 +45,13 @@ public class ProgressCategory extends ProgressCategoryBase {
         textView.setVisibility(noDeviceFound ? View.INVISIBLE : View.VISIBLE);
         progressBar.setVisibility(mProgress ? View.VISIBLE : View.INVISIBLE);
 
-        if (mProgress) {
+        if (mProgress || !noDeviceFound) {
             if (mNoDeviceFoundAdded) {
                 removePreference(mNoDeviceFoundPreference);
                 mNoDeviceFoundAdded = false;
             }
         } else {
-            if (noDeviceFound && !mNoDeviceFoundAdded) {
+            if (!mNoDeviceFoundAdded) {
                 if (mNoDeviceFoundPreference == null) {
                     mNoDeviceFoundPreference = new Preference(getContext());
                     mNoDeviceFoundPreference.setLayoutResource(R.layout.preference_empty_list);
@@ -70,4 +70,3 @@ public class ProgressCategory extends ProgressCategoryBase {
         notifyChanged();
     }
 }
-

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

@@ -33,6 +33,7 @@ public final class DevicePickerFragment extends DeviceListPreferenceFragment {
     private boolean mNeedAuth;
     private String mLaunchPackage;
     private String mLaunchClass;
+    private boolean mStartScanOnResume;
 
     @Override
     void addPreferencesForActivity() {
@@ -50,13 +51,17 @@ public final class DevicePickerFragment extends DeviceListPreferenceFragment {
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         getActivity().setTitle(getString(R.string.device_picker));
+        mStartScanOnResume = (savedInstanceState == null);  // don't start scan after rotation
     }
 
     @Override
     public void onResume() {
         super.onResume();
         addCachedDevices();
+        if (mStartScanOnResume) {
             mLocalAdapter.startScanning(true);
+            mStartScanOnResume = false;
+        }
     }
 
     @Override