Correct ActionBar subtitle on locale change

app/src/main/java/com/zegoggles/smssync/activity/MainActivity.java

@@ -23,6 +23,7 @@
 import android.provider.Telephony.Sms;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
+import android.support.annotation.StringRes;
 import android.support.v4.app.ActivityCompat;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentManager;
@@ -116,13 +117,14 @@ public class MainActivity extends ThemeActivity implements
     private static final int REQUEST_PERMISSIONS_BACKUP_SERVICE = 6;
 
     public static final String EXTRA_PERMISSIONS = "permissions";
-    private static final String SCREEN_TITLE = "title";
+    private static final String SCREEN_TITLE_RES = "titleRes";
 
     private Preferences preferences;
     private AuthPreferences authPreferences;
     private OAuth2Client oauth2Client;
     private Intent fallbackAuthIntent;
     private Intent changeDefaultPackageIntent;
+    private PreferenceTitles preferenceTitles;
 
     @Override
     public void onCreate(Bundle bundle) {
@@ -136,7 +138,7 @@ public void onCreate(Bundle bundle) {
         oauth2Client = new OAuth2Client(authPreferences.getOAuth2ClientId());
         fallbackAuthIntent = new Intent(this, OAuth2WebAuthActivity.class).setData(oauth2Client.requestUrl());
         changeDefaultPackageIntent = new Intent(ACTION_CHANGE_DEFAULT).putExtra(EXTRA_PACKAGE_NAME, getPackageName());
-
+        preferenceTitles = new PreferenceTitles(getResources(), R.xml.preferences);
         preferences = new Preferences(this);
         if (bundle == null) {
             showFragment(new MainSettings(), null);
@@ -237,8 +239,11 @@ public boolean onPreferenceStartFragment(PreferenceFragmentCompat caller, Prefer
         if (LOCAL_LOGV) {
             Log.v(TAG, "onPreferenceStartFragment(" + preference + ")");
         }
-        final Fragment fragment = Fragment.instantiate(this, preference.getFragment(),
-                new BundleBuilder().putString(SCREEN_TITLE, String.valueOf(preference.getTitle())).build());
+        final Fragment fragment = Fragment.instantiate(
+            this,
+            preference.getFragment(),
+            new BundleBuilder().putInt(SCREEN_TITLE_RES, preferenceTitles.getTitleRes(preference.getKey())).build());
+
         showFragment(fragment, preference.getKey());
         return true;
     }
@@ -318,13 +323,13 @@ public boolean onPreferenceStartScreen(PreferenceFragmentCompat caller, Preferen
         onBackStackChanged();
     }
 
-    private @Nullable CharSequence getCurrentTitle() {
+    private @StringRes int getCurrentTitle() {
         final int entryCount = getSupportFragmentManager().getBackStackEntryCount();
         if (entryCount == 0) {
-            return null;
+            return 0;
         } else {
             final BackStackEntry entry = getSupportFragmentManager().getBackStackEntryAt(entryCount - 1);
-            return entry.getBreadCrumbTitle();
+            return entry.getBreadCrumbTitleRes();
         }
     }
 
@@ -409,7 +414,7 @@ private void showFragment(@NonNull Fragment fragment, @Nullable String rootKey)
             .replace(R.id.preferences_container, fragment, rootKey);
         if (rootKey != null) {
             tx.addToBackStack(null);
-            tx.setBreadCrumbTitle(args.getString(SCREEN_TITLE));
+            tx.setBreadCrumbTitle(args.getInt(SCREEN_TITLE_RES));
         }
         tx.commit();
     }

app/src/main/java/com/zegoggles/smssync/activity/PreferenceTitles.java

@@ -0,0 +1,57 @@
+package com.zegoggles.smssync.activity;
+
+import android.content.res.Resources;
+import android.content.res.XmlResourceParser;
+import android.support.annotation.NonNull;
+import android.support.annotation.StringRes;
+import android.support.annotation.XmlRes;
+import org.xmlpull.v1.XmlPullParser;
+import org.xmlpull.v1.XmlPullParserException;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Standard Android preferences don't expose the title resource id. Reparse preferences XML,
+ * key title resources by preference key.
+ */
+class PreferenceTitles {
+    private static final String NS = "http://schemas.android.com/apk/res/android";
+    private static final String PREFERENCE_SCREEN = "PreferenceScreen";
+    private Map<String, Integer> titleResources = new HashMap<String, Integer>();
+
+    PreferenceTitles(@NonNull Resources resources, @XmlRes int preferenceRes) {
+        final XmlResourceParser parser = resources.getXml(preferenceRes);
+        try {
+            while (true) {
+                int type;
+                do {
+                    type = parser.next();
+                } while (type != XmlPullParser.START_TAG && type != XmlPullParser.END_DOCUMENT);
+
+                if (type == XmlPullParser.END_DOCUMENT) {
+                    break;
+                } else if (PREFERENCE_SCREEN.equals(parser.getName()) && parser.getAttributeCount() > 0) {
+                    final @StringRes int titleRes = parser.getAttributeResourceValue(NS, "title", 0);
+                    final String key = parser.getAttributeValue(NS, "key");
+                    if (titleRes > 0 && key != null) {
+                        titleResources.put(key, titleRes);
+                    }
+                }
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        } catch (XmlPullParserException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * @return the string resource id or 0 if not found
+     */
+    @StringRes int getTitleRes(String preferenceKey) {
+        final Integer res = titleResources.get(preferenceKey);
+        return res == null ? 0 : res;
+    }
+}

app/src/test/java/com/zegoggles/smssync/activity/PreferenceTitlesTest.java

@@ -0,0 +1,32 @@
+package com.zegoggles.smssync.activity;
+
+import com.zegoggles.smssync.R;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+
+import static com.google.common.truth.Truth.assertThat;
+
+@RunWith(RobolectricTestRunner.class)
+public class PreferenceTitlesTest {
+    private PreferenceTitles subject;
+
+    @Before
+    public void setUp() throws Exception {
+        subject = new PreferenceTitles(RuntimeEnvironment.application.getResources(), R.xml.preferences);
+    }
+
+    @Test public void testParseValidKey() {
+        final int res = subject.getTitleRes("com.zegoggles.smssync.activity.fragments.AutoBackupSettings");
+        assertThat(res).isGreaterThan(0);
+        String resolved = RuntimeEnvironment.application.getString(res);
+        assertThat(resolved).isEqualTo("Auto backup settings");
+    }
+
+    @Test public void testInvalidKeyReturnsZero() {
+        final int res = subject.getTitleRes("foo.bar.not.found");
+        assertThat(res).isEqualTo(0);
+    }
+}