How to open a new PreferenceFragment from current one, using the new Android-X API?
OK, I've found 2 possible, yet weird, solutions.
I still would like to know if there is an official way to do it, because both solutions are quite weird.
Solution 1
In the main settings preference XML file, for each sub PreferenceScreen, I put an empty Preference tag.
preferences.xml
<PreferenceScreen
android:key="screen_preference" android:summary="Shows another screen of preferences"
android:title="Screen preference">
<Preference/>
</PreferenceScreen>
I pass null for the second argument of setPreferencesFromResource on the new sub-screen fragment.
Here's the code (project available here) :
MainActivity.kt
class MainActivity : AppCompatActivity(), PreferenceFragmentCompat.OnPreferenceStartScreenCallback {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
supportActionBar!!.setDisplayHomeAsUpEnabled(true)
if (savedInstanceState == null)
supportFragmentManager.beginTransaction().replace(android.R.id.content, PrefsFragment()).commit()
}
override fun onPreferenceStartScreen(caller: PreferenceFragmentCompat, pref: PreferenceScreen): Boolean {
supportFragmentManager.beginTransaction().replace(android.R.id.content, PrefsFragment2()).addToBackStack(null).commit()
return true
}
class PrefsFragment : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences, rootKey)
}
}
class PrefsFragment2 : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences2, null)
}
}
}
Of course, this needs to be modified so that you will know which fragment to create and add...
Solution 2
I use a normal Preference instead of each PreferenceScreen, and for each of them I choose to add the fragment upon clicking (project available here) :
preferences.xml
<Preference
android:key="screen_preference" android:summary="Shows another screen of preferences"
android:title="Screen preference"/>
MainActivity.kt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
supportActionBar!!.setDisplayHomeAsUpEnabled(true)
if (savedInstanceState == null)
supportFragmentManager.beginTransaction().replace(android.R.id.content, PrefsFragment()).commit()
}
class PrefsFragment : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences, rootKey)
setPreferenceToOpenFragmentAsNewPage(findPreference("screen_preference"), PrefsFragment2::class.java)
}
private fun setPreferenceToOpenFragmentAsNewPage(pref: Preference, java: Class<out PreferenceFragmentCompat>) {
pref.onPreferenceClickListener = Preference.OnPreferenceClickListener {
val fragment = java.newInstance()
val args = Bundle(1)
args.putString(PreferenceFragmentCompat.ARG_PREFERENCE_ROOT, pref.key)
fragment.arguments = args
activity!!.supportFragmentManager.beginTransaction().replace(android.R.id.content, fragment).addToBackStack(null).commit()
true
}
}
}
class PrefsFragment2 : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences2, null)
}
}
}
EDIT: a tiny modification to the second solution can make it nicer:
preferences.xml
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:title="Demo">
<Preference
android:fragment="com.example.user.myapplication.MainActivity$PrefsFragment2" android:key="screen_preference"
android:summary="Shows another screen of preferences" android:title="Screen preference"/>
</PreferenceScreen>
MainActivity.kt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
supportActionBar!!.setDisplayHomeAsUpEnabled(true)
if (savedInstanceState == null)
supportFragmentManager.beginTransaction().replace(android.R.id.content, PrefsFragment()).commit()
}
class PrefsFragment : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences, rootKey)
setPreferenceToOpenFragmentAsNewPage(findPreference("screen_preference"))
}
private fun setPreferenceToOpenFragmentAsNewPage(pref: Preference) {
pref.onPreferenceClickListener = Preference.OnPreferenceClickListener {
val clazz = Class.forName(pref.fragment)
val fragment: PreferenceFragmentCompat = clazz.newInstance() as PreferenceFragmentCompat
val args = Bundle(1)
args.putString(PreferenceFragmentCompat.ARG_PREFERENCE_ROOT, pref.key)
fragment.arguments = args
activity!!.supportFragmentManager.beginTransaction().replace(android.R.id.content, fragment).addToBackStack(null).commit()
true
}
}
}
class PrefsFragment2 : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences2, null)
}
}
}
Note that you need to add this to Proguard rules:
-keepnames public class * extends androidx.preference.PreferenceFragmentCompat
Another improvement to solution #2 is that it can go over all preferences by itself:
class PrefsFragment : BasePreferenceFragment() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences_headers, rootKey)
val preferenceScreen = preferenceScreen
val preferenceCount = preferenceScreen.preferenceCount
for (i in 0 until preferenceCount) {
val pref = preferenceScreen.getPreference(i)
val fragmentClassName = pref.fragment
if (fragmentClassName.isNullOrEmpty())
continue
pref.setOnPreferenceClickListener {
showPreferenceFragment(activity!!, fragmentClassName)
true
}
}
}
}
companion object {
@JvmStatic
private fun showPreferenceFragment(activity: FragmentActivity, fragmentClassName: String) {
val clazz = Class.forName(fragmentClassName)
val fragment: PreferenceFragmentCompat = clazz.newInstance() as PreferenceFragmentCompat
val fragmentsCount = activity.supportFragmentManager.fragments.size
val transaction = activity.supportFragmentManager.beginTransaction().replace(android.R.id.content, fragment)
if (fragmentsCount > 0)
transaction.addToBackStack(null)
transaction.commit()
}
}
EDIT: seems the first solution was the correct one, but needed a change. Check the answer here. Full sample available here.
What you tried in 1) was the correct approach - but you should not use <PreferenceScreen> tags for this.
Your XML resource should look like this instead:
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<Preference
app:key="screen_preference"
app:summary="Shows another screen of preferences"
app:title="Screen preference"
app:fragment="com.example.user.myapplication.MainActivity$PrefsFragment2"/>
</PreferenceScreen>
Also, if you are using a version of Preference older than androidx.preference:preference:1.1.0-alpha01, you will need to implement onPreferenceStartFragment to handle the fragment transaction. (in 1.1.0 alpha01 this method has a default implementation, but you are still encouraged to use your own implementation to customize any animations / transitions)
This should look something like:
override fun onPreferenceStartFragment(
caller: PreferenceFragmentCompat,
pref: Preference
): Boolean {
// Instantiate the new Fragment
val args = pref.extras
val fragment = supportFragmentManager.fragmentFactory.instantiate(
classLoader,
pref.fragment,
args
).apply {
arguments = args
setTargetFragment(caller, 0)
}
// Replace the existing Fragment with the new Fragment
supportFragmentManager.beginTransaction()
.replace(R.id.settings, fragment)
.addToBackStack(null)
.commit()
return true
}
For more information you can check out the Settings guide and the AndroidX Preference Sample
EDIT: a sample of the first solution, after updating, available here.
Here's how it can work (sample available here) :
MainActivity.kt
class MainActivity : AppCompatActivity(), PreferenceFragmentCompat.OnPreferenceStartFragmentCallback {
override fun onPreferenceStartFragment(caller: PreferenceFragmentCompat, pref: Preference): Boolean {
//Note: this whole function won't be needed when using new version of fragment dependency (1.1.0 and above)
val fragment = Fragment.instantiate(this, pref.fragment, pref.extras)
fragment.setTargetFragment(caller, 0)
supportFragmentManager.beginTransaction().replace(android.R.id.content, fragment).addToBackStack(null).commit()
return true
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
supportActionBar!!.setDisplayHomeAsUpEnabled(true)
if (savedInstanceState == null)
supportFragmentManager.beginTransaction().replace(android.R.id.content, PrefsFragment()).commit()
}
class PrefsFragment : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences, rootKey)
}
}
class PrefsFragment2 : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences2, null)
}
}
}
preferences.xml
<PreferenceScreen xmlns:app="http://schemas.android.com/apk/res-auto">
<Preference
app:fragment="com.example.user.myapplication.MainActivity$PrefsFragment2" app:key="screen_preference" app:summary="Shows another screen of preferences"
app:title="Screen preference"/>
</PreferenceScreen>
preferences2.xml
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:title="Demo">
<PreferenceCategory android:title="Category">
<CheckBoxPreference
android:key="next_screen_checkbox_preference" android:summary="AAAA" android:title="Toggle preference"/>
</PreferenceCategory>
</PreferenceScreen>
gradle dependencies:
implementation 'androidx.appcompat:appcompat:1.0.2'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'androidx.preference:preference:1.0.0'
FYI, if you are using Navigation drawer + androidx.appcompat, you can:
1) Split each PreferenceScreen child into as many as preference.xml file: ie "Pref_general.xml" will be the main preference and "pref_ServerSettings.xml" contains the PreferenceScreen child with you server settings. 2) Create a PreferenceFragmentCompat for each preference.xml:
"PrefFragmentGeneral"
On your PrefFragmentGeneral.xml file, add a Preference instead of a PreferenceScreen like bellow, for any sub xml:
<Preference
android:key="pref_serverPref"
android:summary="@string/settings_serverPrefSum"
android:title="@string/settings_serverPrefTitle"
/>
"PrefFragmentServer"
2) Ensure you override "onCreatePreferences" to set preferences from the XML file you would like:
public class PrefFragmentGeneral extends PreferenceFragmentCompat {
@Override
public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
setPreferencesFromResource(R.xml.Pref_general, rootKey);
//find your preference(s) using the same key
Preference serverPref=findPreference("pref_serverPref");
if(serverPref!=null){
//Assign the click listener to navigate to the fragment using the navigation controller
serverPref.setOnPreferenceClickListener(preference -> {
NavController navController = Navigation.findNavController(getActivity(), R.id.nav_host_fragment);
navController.navigate(R.id.nav_PrefFragmentServer);
return true;
});
}
}
//and the PrefFragmentServer
public class PrefFragmentServer extends PreferenceFragmentCompat {
@Override
public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
setPreferencesFromResource(R.xml.pref_ServerSettings,rootKey);
}
}
3) Register all your fragments inside your navigation drawer:
Now enjoy!
Pros: When you navigate back, you go back to the "General" preference as if you where coming back to a PreferenceActivity children! AND you don't get an exception telling you that the fragment is not part of FragmentManager.