AccountSettingsActivity: use loader

* use Loader for AccountSettingsActivity sync intervals (fixes Android 7 display "issues")
* SyncManager: allow prepare() to skip synchronization

app/src/main/java/at/bitfire/davdroid/syncadapter/CalendarSyncManager.java

@@ -61,8 +61,9 @@ public class CalendarSyncManager extends SyncManager {
     }
 
     @Override
-    protected void prepare() throws ContactsStorageException {
+    protected boolean prepare() throws ContactsStorageException {
         journal = new JournalEntryManager(httpClient, remote, localCalendar().getName());
+        return true;
     }
 
     @Override

app/src/main/java/at/bitfire/davdroid/syncadapter/ContactsSyncManager.java

@@ -75,7 +75,7 @@ public class ContactsSyncManager extends SyncManager {
     }
 
     @Override
-    protected void prepare() throws ContactsStorageException, CalendarStorageException {
+    protected boolean prepare() throws ContactsStorageException, CalendarStorageException {
         // prepare local address book
         localCollection = new LocalAddressBook(account, provider);
         LocalAddressBook localAddressBook = localAddressBook();
@@ -88,6 +88,8 @@ public class ContactsSyncManager extends SyncManager {
         localAddressBook.updateSettings(values);
 
         journal = new JournalEntryManager(httpClient, remote, info.url);
+
+        return true;
     }
 
     @Override

app/src/main/java/at/bitfire/davdroid/syncadapter/SyncManager.java

@@ -124,7 +124,10 @@ abstract public class SyncManager {
         String syncPhase = SYNC_PHASE_PREPARE;
         try {
             App.log.info("Sync phase: " + syncPhase);
-            prepare();
+            if (!prepare()) {
+                App.log.info("No reason to synchronize, aborting");
+                return;
+            }
 
             if (Thread.interrupted())
                 return;
@@ -219,7 +222,10 @@ abstract public class SyncManager {
     }
 
 
-    abstract protected void prepare() throws ContactsStorageException, CalendarStorageException;
+    /** Prepares synchronization (for instance, allocates necessary resources).
+     * @return whether actual synchronization is required / can be made. true = synchronization
+     *         shall be continued, false = synchronization can be skipped */
+    abstract protected boolean prepare() throws ContactsStorageException, CalendarStorageException;
 
     abstract protected void processSyncEntry(SyncEntry cEntry) throws IOException, ContactsStorageException, CalendarStorageException, InvalidCalendarException;
 

app/src/main/java/at/bitfire/davdroid/ui/AccountSettingsActivity.java

@@ -9,11 +9,17 @@
 package at.bitfire.davdroid.ui;
 
 import android.accounts.Account;
+import android.content.ContentResolver;
+import android.content.Context;
 import android.content.Intent;
+import android.content.SyncStatusObserver;
 import android.os.Bundle;
 import android.provider.CalendarContract;
 import android.provider.ContactsContract;
+import android.support.v4.app.LoaderManager;
 import android.support.v4.app.NavUtils;
+import android.support.v4.content.AsyncTaskLoader;
+import android.support.v4.content.Loader;
 import android.support.v7.app.AppCompatActivity;
 import android.support.v7.preference.EditTextPreference;
 import android.support.v7.preference.ListPreference;
@@ -23,10 +29,7 @@ import android.support.v7.preference.SwitchPreferenceCompat;
 import android.text.TextUtils;
 import android.view.MenuItem;
 
-import java.util.logging.Level;
-
 import at.bitfire.davdroid.AccountSettings;
-import at.bitfire.davdroid.App;
 import at.bitfire.davdroid.InvalidAccountException;
 import at.bitfire.davdroid.R;
 import at.bitfire.davdroid.ui.setup.DetectConfigurationFragment;
@@ -66,7 +69,7 @@ public class AccountSettingsActivity extends AppCompatActivity {
     }
 
 
-    public static class AccountSettingsFragment extends PreferenceFragmentCompat {
+    public static class AccountSettingsFragment extends PreferenceFragmentCompat implements LoaderManager.LoaderCallbacks<AccountSettings> {
         Account account;
 
         @Override
@@ -74,7 +77,8 @@ public class AccountSettingsActivity extends AppCompatActivity {
             super.onCreate(savedInstanceState);
 
             account = getArguments().getParcelable(EXTRA_ACCOUNT);
-            refresh();
+
+            getLoaderManager().initLoader(0, getArguments(), this);
         }
 
         @Override
@@ -82,13 +86,14 @@ public class AccountSettingsActivity extends AppCompatActivity {
             addPreferencesFromResource(R.xml.settings_account);
         }
 
-        public void refresh() {
+        @Override
-            final AccountSettings settings;
+        public Loader<AccountSettings> onCreateLoader(int id, Bundle args) {
+            return new AccountSettingsLoader(getContext(), (Account)args.getParcelable(EXTRA_ACCOUNT));
+        }
 
-            try {
+        @Override
-                settings = new AccountSettings(getActivity(), account);
+        public void onLoadFinished(Loader<AccountSettings> loader, final AccountSettings settings) {
-            } catch(InvalidAccountException e) {
+            if (settings == null) {
-                App.log.log(Level.INFO, "Account is invalid or doesn't exist (anymore)", e);
                 getActivity().finish();
                 return;
             }
@@ -100,7 +105,7 @@ public class AccountSettingsActivity extends AppCompatActivity {
                 public boolean onPreferenceChange(Preference preference, Object newValue) {
                     LoginCredentials credentials = newValue != null ? new LoginCredentials(account.name, (String) newValue) : null;
                     LoginCredentialsChangeFragment.newInstance(account, credentials).show(getFragmentManager(), null);
-                    refresh();
+                    getLoaderManager().restartLoader(0, getArguments(), AccountSettingsFragment.this);
                     return false;
                 }
             });
@@ -118,7 +123,7 @@ public class AccountSettingsActivity extends AppCompatActivity {
                     @Override
                     public boolean onPreferenceChange(Preference preference, Object newValue) {
                         settings.setSyncInterval(ContactsContract.AUTHORITY, Long.parseLong((String)newValue));
-                        refresh();
+                        getLoaderManager().restartLoader(0, getArguments(), AccountSettingsFragment.this);
                         return false;
                     }
                 });
@@ -139,7 +144,7 @@ public class AccountSettingsActivity extends AppCompatActivity {
                     @Override
                     public boolean onPreferenceChange(Preference preference, Object newValue) {
                         settings.setSyncInterval(CalendarContract.AUTHORITY, Long.parseLong((String)newValue));
-                        refresh();
+                        getLoaderManager().restartLoader(0, getArguments(), AccountSettingsFragment.this);
                         return false;
                     }
                 });
@@ -160,7 +165,7 @@ public class AccountSettingsActivity extends AppCompatActivity {
                     @Override
                     public boolean onPreferenceChange(Preference preference, Object newValue) {
                         settings.setSyncInterval(TaskProvider.ProviderName.OpenTasks.authority, Long.parseLong((String)newValue));
-                        refresh();
+                        getLoaderManager().restartLoader(0, getArguments(), AccountSettingsFragment.this);
                         return false;
                     }
                 });
@@ -175,7 +180,7 @@ public class AccountSettingsActivity extends AppCompatActivity {
                 @Override
                 public boolean onPreferenceChange(Preference preference, Object wifiOnly) {
                     settings.setSyncWiFiOnly((Boolean)wifiOnly);
-                    refresh();
+                    getLoaderManager().restartLoader(0, getArguments(), AccountSettingsFragment.this);
                     return false;
                 }
             });
@@ -192,11 +197,57 @@ public class AccountSettingsActivity extends AppCompatActivity {
                 public boolean onPreferenceChange(Preference preference, Object newValue) {
                     String ssid = (String)newValue;
                     settings.setSyncWifiOnlySSID(!TextUtils.isEmpty(ssid) ? ssid : null);
-                    refresh();
+                    getLoaderManager().restartLoader(0, getArguments(), AccountSettingsFragment.this);
                     return false;
                 }
             });
         }
+
+        @Override
+        public void onLoaderReset(Loader<AccountSettings> loader) {
+        }
+
+    }
+
+
+    private static class AccountSettingsLoader extends AsyncTaskLoader<AccountSettings> implements SyncStatusObserver {
+
+        final Account account;
+        Object listenerHandle;
+
+        public AccountSettingsLoader(Context context, Account account) {
+            super(context);
+            this.account = account;
+        }
+
+        @Override
+        protected void onStartLoading() {
+            forceLoad();
+
+            listenerHandle = ContentResolver.addStatusChangeListener(ContentResolver.SYNC_OBSERVER_TYPE_SETTINGS, this);
+        }
+
+        @Override
+        protected void onStopLoading() {
+            ContentResolver.removeStatusChangeListener(listenerHandle);
+        }
+
+        @Override
+        public AccountSettings loadInBackground() {
+            AccountSettings settings;
+            try {
+                settings = new AccountSettings(getContext(), account);
+            } catch(InvalidAccountException e) {
+                return null;
+            }
+            return settings;
+        }
+
+        @Override
+        public void onStatusChanged(int which) {
+            forceLoad();
+        }
+
     }
 
 }