maxdownunder maxdownunder - 4 months ago 123
Android Question

Preference sub-screen not opening when using support.v7.preference

I am trying to implement preferences with sub-screens using AppCompatActivity and support.v7.preference

According to the docs, every PreferenceScreen within another PreferenceScreen functions as a sub-screen, and the framework will handle displaying it when clicked.
http://developer.android.com/guide/topics/ui/settings.html#Subscreens

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<!-- opens a subscreen of settings -->
<PreferenceScreen
android:key="button_voicemail_category_key"
android:title="@string/voicemail"
android:persistent="false">
<ListPreference
android:key="button_voicemail_provider_key"
android:title="@string/voicemail_provider" ... />
<!-- opens another nested subscreen -->
<PreferenceScreen
android:key="button_voicemail_setting_key"
android:title="@string/voicemail_settings"
android:persistent="false">
...
</PreferenceScreen>
<RingtonePreference
android:key="button_voicemail_ringtone_key"
android:title="@string/voicemail_ringtone_title"
android:ringtoneType="notification" ... />
...
</PreferenceScreen>
...
</PreferenceScreen>


This works fine using native Activity, PreferenceFragment... but using AppCompatActivity and PreferenceFragmentCompat, clicking the Preference element just highlights it, but doesn't open the sub-screen.

I couldn't find anything on this reading the docs and the code... do I need to implement any additional callbacks?




EDIT: just for completeness...

This works and opens the sub-screen:

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.replace(android.R.id.content, new DemoPreferenceFragment())
.commit();
}
}

static public class DemoPreferenceFragment extends PreferenceFragment {

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
}
}
}


This doesn't work/open the sub-screen:

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.replace(android.R.id.content, new DemoPreferenceFragment())
.commit();
}
}

static public class DemoPreferenceFragment extends PreferenceFragmentCompat {

@Override
public void onCreatePreferences(Bundle bundle, String s) {
addPreferencesFromResource(R.xml.preferences);
}
}
}





Edit: 25/01/2016

After fiddling with support.v7.preference for a few days, I've summed up my findings here, hoping it may help others:
HowTo use support.v7.preference with AppCompat and potential drawbacks

Answer

It looks like a bug in PreferenceFragmentCompat or insufficiency of docs. It has method onNavigateToScreen which is called when you click on PreferenceScreen item.

But method getCallbackFragment() returns null by default, so you need override it in your fragment to return this. Also you need to implement PreferenceFragmentCompat.OnPreferenceStartScreenCallback.

public class SettingsFragment extends PreferenceFragmentCompat implements PreferenceFragmentCompat.OnPreferenceStartScreenCallback {

    public static SettingsFragment newInstance() {
        return new SettingsFragment();
    }

    @Override
    public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
        addPreferencesFromResource(R.xml.news_settings);
    }

    @Override
    public Fragment getCallbackFragment() {
        return this;
    }

    @Override
    public boolean onPreferenceStartScreen(PreferenceFragmentCompat preferenceFragmentCompat, PreferenceScreen preferenceScreen) {
        preferenceFragmentCompat.setPreferenceScreen(preferenceScreen);
        return true;
    }
}

But it leads to another problem when you can't get back to your initial PreferenceScreen,

Another way is to replace fragment which is described here How to move back from Preferences subscreen to main screen in PreferenceFragmentCompat?