lineage-sdk: Use PreferenceDataStore for lineage-sdk preferences

Replaces the need for:
32e67e6020

*) frameworks/support are now built with gradle and are included as prebuilts.

*) API level 26 (8.0) introduced PreferenceDataStorage which can be used
   to implement what we need without touching the support library.

Change-Id: Ide3417019ccf8bde5dca3b2aec3d2075e7c8b597

sdk/src/java/lineageos/preference/SelfRemovingListPreference.java

@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2016 The CyanogenMod Project
+ * Copyright (C) 2018 The LineageOS Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +18,7 @@ package lineageos.preference;
 
 import android.content.Context;
 import android.support.v7.preference.ListPreference;
+import android.support.v7.preference.PreferenceDataStore;
 import android.support.v7.preference.PreferenceViewHolder;
 import android.util.AttributeSet;
 
@@ -24,23 +26,26 @@ import android.util.AttributeSet;
  * A Preference which can automatically remove itself from the hierarchy
  * based on constraints set in XML.
  */
-public class SelfRemovingListPreference extends ListPreference {
+public abstract class SelfRemovingListPreference extends ListPreference {
 
     private final ConstraintsHelper mConstraints;
 
     public SelfRemovingListPreference(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         mConstraints = new ConstraintsHelper(context, attrs, this);
+        setPreferenceDataStore(new DataStore());
     }
 
     public SelfRemovingListPreference(Context context, AttributeSet attrs) {
         super(context, attrs);
         mConstraints = new ConstraintsHelper(context, attrs, this);
+        setPreferenceDataStore(new DataStore());
     }
 
     public SelfRemovingListPreference(Context context) {
         super(context);
         mConstraints = new ConstraintsHelper(context, null, this);
+        setPreferenceDataStore(new DataStore());
     }
 
     @Override
@@ -63,4 +68,38 @@ public class SelfRemovingListPreference extends ListPreference {
         return mConstraints.isAvailable();
     }
 
+    protected abstract boolean isPersisted();
+    protected abstract void putString(String key, String value);
+    protected abstract String getString(String key, String defaultValue);
+
+    @Override
+    protected void onSetInitialValue(boolean restorePersistedValue, Object defaultValue) {
+        final String value;
+        if (!restorePersistedValue || !isPersisted()) {
+            if (defaultValue == null) {
+                return;
+            }
+            value = (String) defaultValue;
+            if (shouldPersist()) {
+                persistString(value);
+            }
+        } else {
+            // Note: the default is not used because to have got here
+            // isPersisted() must be true.
+            value = getString(getKey(), null /* not used */);
+        }
+        setValue(value);
+    }
+
+    private class DataStore extends PreferenceDataStore {
+        @Override
+        public void putString(String key, String value) {
+            SelfRemovingListPreference.this.putString(key, value);
+        }
+
+        @Override
+        public String getString(String key, String defaultValue) {
+            return SelfRemovingListPreference.this.getString(key, defaultValue);
+        }
+    }
 }