Add example code for preference fragment

Thanks #41 for example code

app/src/main/AndroidManifest.xml

@@ -23,6 +23,7 @@
         <activity android:name=".customactivity.SimpleCustomActivity" />
         <activity android:name=".stackedactivity.Stack1Activity" />
         <activity android:name=".stackedactivity.Stack2Activity" />
+        <activity android:name=".preferences.ListPreferencesActivity" />
     </application>
 
 </manifest>

app/src/main/java/com/akexorcist/localizationapp/MainActivity.java

@@ -7,6 +7,7 @@
 import com.akexorcist.localizationactivity.ui.LocalizationActivity;
 import com.akexorcist.localizationapp.customactivity.SimpleCustomActivity;
 import com.akexorcist.localizationapp.nestedfragment.NestedFragmentActivity;
+import com.akexorcist.localizationapp.preferences.ListPreferencesActivity;
 import com.akexorcist.localizationapp.simpleactivity.SimpleActivity;
 import com.akexorcist.localizationapp.simplefragment.SimpleFragmentActivity;
 import com.akexorcist.localizationapp.stackedactivity.Stack1Activity;
@@ -25,6 +26,7 @@ public void onCreate(Bundle savedInstanceState) {
         findViewById(R.id.btn_activity_fragment).setOnClickListener(onSimpleFragmentClick());
         findViewById(R.id.btn_activity_nested_fragment).setOnClickListener(onNestedFragmentClick());
         findViewById(R.id.btn_activity_view_pager).setOnClickListener(onViewPagerClick());
+        findViewById(R.id.btn_activity_list_preferences).setOnClickListener(onPreferenceFragmentClick());
     }
 
     public View.OnClickListener onSimpleActivityClick() {
@@ -51,6 +53,10 @@ public View.OnClickListener onViewPagerClick() {
         return view -> goToActivity(ViewPagerActivity.class);
     }
 
+    public View.OnClickListener onPreferenceFragmentClick() {
+        return view -> goToActivity(ListPreferencesActivity.class);
+    }
+
     public void goToActivity(Class<?> activity) {
         Intent intent = new Intent(this, activity);
         startActivity(intent);

app/src/main/java/com/akexorcist/localizationapp/preferences/LanguagePreferenceFragment.kt

@@ -0,0 +1,26 @@
+package com.akexorcist.localizationapp.preferences
+
+import android.os.Bundle
+import androidx.preference.Preference
+import androidx.preference.PreferenceFragmentCompat
+import com.akexorcist.localizationapp.R
+
+class LanguagePreferenceFragment : PreferenceFragmentCompat() {
+    companion object {
+        private const val KEY_PREFERENCE_LANGUAGE = "language"
+    }
+
+    override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
+        setPreferencesFromResource(R.xml.settings, rootKey)
+        setHasOptionsMenu(false)
+        findPreference<Preference>(KEY_PREFERENCE_LANGUAGE)?.setOnPreferenceChangeListener { _, newValue ->
+            val language = newValue.toString()
+            (activity as PreferenceChangeListener).onLanguagePreferenceChanged(language)
+            true
+        }
+    }
+
+    interface PreferenceChangeListener {
+        fun onLanguagePreferenceChanged(langauge: String)
+    }
+}

app/src/main/java/com/akexorcist/localizationapp/preferences/ListPreferencesActivity.kt

@@ -0,0 +1,17 @@
+package com.akexorcist.localizationapp.preferences
+
+import android.os.Bundle
+import com.akexorcist.localizationactivity.ui.LocalizationActivity
+import com.akexorcist.localizationapp.R
+
+class ListPreferencesActivity : LocalizationActivity(), LanguagePreferenceFragment.PreferenceChangeListener {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_list_preferences)
+        supportFragmentManager.beginTransaction().replace(R.id.layoutFragmentContainer, LanguagePreferenceFragment()).commit()
+    }
+
+    override fun onLanguagePreferenceChanged(langauge: String) {
+        setLanguage(langauge)
+    }
+}

app/src/main/res/layout/activity_list_preferences.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".preferences.ListPreferencesActivity">
+    <FrameLayout
+        android:id="@+id/layoutFragmentContainer"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:paddingBottom="?attr/actionBarSize" />
+</FrameLayout>

app/src/main/res/layout/activity_main.xml

@@ -64,6 +64,12 @@
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:text="@string/viewpager_activity" />
+
+            <Button
+                android:id="@+id/btn_activity_list_preferences"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:text="@string/list_preferences_activity" />
         </LinearLayout>
     </LinearLayout>
 </ScrollView>

app/src/main/res/values/settings_strings.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string-array name="pref_language_list_titles" translatable="false">
+        <item>America</item>
+        <item>China</item>
+        <item>Italy</item>
+        <item>Japan</item>
+        <item>Korea</item>
+        <item>Portugal</item>
+        <item>Thai</item>
+    </string-array>
+    <string-array name="pref_language_list_values" translatable="false">
+        <item>en</item>
+        <item>zh</item>
+        <item>it</item>
+        <item>ja</item>
+        <item>ko</item>
+        <item>pt</item>
+        <item>th</item>
+    </string-array>
+</resources>

app/src/main/res/values/strings.xml

@@ -23,6 +23,7 @@
     <string name="nested_fragment_activity" translatable="false">Activity + Nested Fragment</string>
     <string name="viewpager_activity" translatable="false">Activity + View Pager</string>
     <string name="viewpager_description" translatable="false">Swipe or click to change page</string>
+    <string name="list_preferences_activity" translatable="false">Activity + Preference Fragment</string>
 
     <string name="america" translatable="false">America</string>
     <string name="china" translatable="false">China</string>

app/src/main/res/xml/settings.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
+    <PreferenceCategory android:title="@string/hello_world">
+        <ListPreference
+            android:defaultValue="en"
+            android:entries="@array/pref_language_list_titles"
+            android:entryValues="@array/pref_language_list_values"
+            android:key="language"
+            android:negativeButtonText="@null"
+            android:positiveButtonText="@null"
+            android:title="@string/change_language" />
+    </PreferenceCategory>
+</PreferenceScreen>