Update display logic for no shared data.

When there is no shared data, instead of showing an empty list view,
the developer option's summary is updated.

Additionally, for the two shared data screens, added the back button to
the action bar so that it matches the other screens in the Settings app.

Also, implemented PreferenceControllerMixin for the
SharedDataPreferenceController so that the dev option shows up in
settings search.

Bug: 153079829
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SharedDataPreferenceControllerTest
Test: manual (visual)
Change-Id: I6ec5c35fc262dc27a383af8e2593be5b349ee85f

src/com/android/settings/development/storage/BlobInfoListView.java

@@ -16,6 +16,7 @@
 
 package com.android.settings.development.storage;
 
+import android.app.ActionBar;
 import android.app.ListActivity;
 import android.app.blob.BlobInfo;
 import android.app.blob.BlobStoreManager;
@@ -30,7 +31,6 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ArrayAdapter;
 import android.widget.ListView;
-import android.widget.TextView;
 import android.widget.Toast;
 
 import androidx.appcompat.app.AlertDialog;
@@ -41,7 +41,6 @@ import com.android.settings.R;
 import java.io.IOException;
 import java.util.List;
 
-// TODO: have this class extend DashboardFragment for consistency
 public class BlobInfoListView extends ListActivity {
     private static final String TAG = "BlobInfoListView";
 
@@ -60,6 +59,17 @@ public class BlobInfoListView extends ListActivity {
 
         mAdapter = new BlobListAdapter(this);
         setListAdapter(mAdapter);
+
+        final ActionBar actionBar = getActionBar();
+        if (actionBar != null) {
+            actionBar.setDisplayHomeAsUpEnabled(true);
+        }
+    }
+
+    @Override
+    public boolean onNavigateUp() {
+        finish();
+        return true;
     }
 
     @Override
@@ -91,14 +101,6 @@ public class BlobInfoListView extends ListActivity {
         }
     }
 
-    private View getEmptyView() {
-        final View emptyView = mInflater.inflate(R.layout.shared_data_empty_list_view,
-                (ViewGroup) getListView().getRootView());
-        final TextView emptyText = emptyView.findViewById(R.id.empty_view_text);
-        emptyText.setText(R.string.shared_data_no_blobs_text);
-        return emptyView;
-    }
-
     private void showDeleteBlobDialog(BlobInfo blob) {
         final AlertDialog dialog = new AlertDialog.Builder(mContext)
                 .setMessage(R.string.shared_data_no_accessors_dialog_text)
@@ -139,7 +141,7 @@ public class BlobInfoListView extends ListActivity {
         void updateList(List<BlobInfo> blobs) {
             clear();
             if (blobs.isEmpty()) {
-                getListView().setEmptyView(getEmptyView());
+                finish();
             } else {
                 addAll(blobs);
             }

src/com/android/settings/development/storage/LeaseInfoListView.java

@@ -16,6 +16,7 @@
 
 package com.android.settings.development.storage;
 
+import android.app.ActionBar;
 import android.app.ListActivity;
 import android.app.blob.BlobInfo;
 import android.app.blob.BlobStoreManager;
@@ -44,7 +45,6 @@ import com.android.settings.R;
 import java.io.IOException;
 import java.util.List;
 
-// TODO: have this class extend DashboardFragment for consistency
 public class LeaseInfoListView extends ListActivity {
     private static final String TAG = "LeaseInfoListView";
 
@@ -74,6 +74,17 @@ public class LeaseInfoListView extends ListActivity {
         getListView().addHeaderView(getHeaderView());
         getListView().addFooterView(getFooterView());
         getListView().setClickable(false);
+
+        final ActionBar actionBar = getActionBar();
+        if (actionBar != null) {
+            actionBar.setDisplayHomeAsUpEnabled(true);
+        }
+    }
+
+    @Override
+    public boolean onNavigateUp() {
+        finish();
+        return true;
     }
 
     private LinearLayout getHeaderView() {

src/com/android/settings/development/storage/SharedDataPreferenceController.java

@@ -18,13 +18,20 @@ package com.android.settings.development.storage;
 
 import android.app.blob.BlobStoreManager;
 import android.content.Context;
+import android.os.UserHandle;
+import android.util.Log;
 
 import androidx.preference.Preference;
 
+import com.android.settings.R;
+import com.android.settings.core.PreferenceControllerMixin;
 import com.android.settingslib.development.DeveloperOptionsPreferenceController;
 
-public class SharedDataPreferenceController extends DeveloperOptionsPreferenceController {
+import java.io.IOException;
 
+public class SharedDataPreferenceController extends DeveloperOptionsPreferenceController
+        implements PreferenceControllerMixin {
+    private static final String TAG = "SharedDataPrefCtrl";
     private static final String SHARED_DATA = "shared_data";
 
     private BlobStoreManager mBlobStoreManager;
@@ -39,14 +46,18 @@ public class SharedDataPreferenceController extends DeveloperOptionsPreferenceCo
         return SHARED_DATA;
     }
 
-    @Override
-    public boolean isAvailable() {
-        return mBlobStoreManager != null;
-    }
-
     @Override
     public void updateState(Preference preference) {
-        preference.setEnabled(mBlobStoreManager != null);
-        // TODO: update summary to indicate why this preference isn't available
+        try {
+            final boolean showPref = mBlobStoreManager != null
+                    && !mBlobStoreManager.queryBlobsForUser(UserHandle.CURRENT).isEmpty();
+            preference.setEnabled(showPref);
+            preference.setSummary(showPref ? R.string.shared_data_summary
+                                           : R.string.shared_data_no_blobs_text);
+        } catch (IOException e) {
+            Log.e(TAG, "Unable to fetch blobs for current user: " + e.getMessage());
+            preference.setEnabled(false);
+            preference.setSummary(R.string.shared_data_no_blobs_text);
+        }
     }
 }