diff --git a/src/main/res/values/attrs.xml b/src/main/res/values/attrs.xml
index cb3046aa..1ce9d120 100644
--- a/src/main/res/values/attrs.xml
+++ b/src/main/res/values/attrs.xml
@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <declare-styleable name="DropDownPreference">
-        <attr name="entries" format="reference" />
-        <attr name="entryValues" format="reference" />
+        <attr name="android:entries" />
+        <attr name="android:entryValues" />
     </declare-styleable>
     <declare-styleable name="NumberPickerPreference">
         <attr name="max" format="integer" />
diff --git a/src/main/res/xml/pref_all.xml b/src/main/res/xml/pref_all.xml
index fb1246ba..c6689417 100644
--- a/src/main/res/xml/pref_all.xml
+++ b/src/main/res/xml/pref_all.xml
@@ -37,8 +37,8 @@
         <com.github.shadowsocks.preferences.DropDownPreference
                 android:key="encMethod"
                 android:persistent="false"
-                app:entries="@array/enc_method_entry"
-                app:entryValues="@array/enc_method_value"
+                android:entries="@array/enc_method_entry"
+                android:entryValues="@array/enc_method_value"
                 android:summary="%s"
                 android:title="@string/enc_method"/>
         <SwitchPreference
@@ -55,8 +55,8 @@
         <com.github.shadowsocks.preferences.DropDownPreference
                 android:key="route"
                 android:persistent="false"
-                app:entries="@array/route_entry"
-                app:entryValues="@array/route_value"
+                android:entries="@array/route_entry"
+                android:entryValues="@array/route_value"
                 android:summary="%s"
                 android:title="@string/route_list"/>
         <SwitchPreference
diff --git a/src/main/scala/com/github/shadowsocks/preferences/DropDownPreference.scala b/src/main/scala/com/github/shadowsocks/preferences/DropDownPreference.scala
index 80abe315..4e88fd52 100644
--- a/src/main/scala/com/github/shadowsocks/preferences/DropDownPreference.scala
+++ b/src/main/scala/com/github/shadowsocks/preferences/DropDownPreference.scala
@@ -5,7 +5,7 @@ import android.content.Context
 import android.content.res.TypedArray
 import android.os.Build
 import android.preference.Preference
-import android.support.annotation.NonNull
+import android.support.annotation.{ArrayRes, NonNull}
 import android.support.v7.widget.AppCompatSpinner
 import android.util.AttributeSet
 import android.view.{View, ViewGroup}
@@ -23,14 +23,16 @@ final class DropDownPreference(private val mContext: Context, attrs: AttributeSe
   private val mSpinner = new AppCompatSpinner(mContext)
   private var mEntries: Array[CharSequence] = _
   private var mEntryValues: Array[CharSequence] = _
-  private var mSelectedIndex: Int = _
-  private var mValueSet: Boolean = _
+  private var mSelectedIndex: Int = -1
 
   mSpinner.setVisibility(View.INVISIBLE)
   mSpinner.setAdapter(mAdapter)
   mSpinner.setOnItemSelectedListener(new OnItemSelectedListener {
-    override def onNothingSelected(parent: AdapterView[_]) { }
-    override def onItemSelected(parent: AdapterView[_], view: View, position: Int, id: Long) = setValueIndex(position)
+    def onNothingSelected(parent: AdapterView[_]) { }
+    def onItemSelected(parent: AdapterView[_], view: View, position: Int, id: Long) = {
+      val value = getValue(position)
+      if (position != mSelectedIndex && callChangeListener(value)) setValue(position, value)
+    }
   })
   setOnPreferenceClickListener((preference: Preference) => {
     // TODO: not working with scrolling
@@ -39,8 +41,8 @@ final class DropDownPreference(private val mContext: Context, attrs: AttributeSe
     true
   })
   val a: TypedArray = mContext.obtainStyledAttributes(attrs, R.styleable.DropDownPreference)
-  setEntries(a.getTextArray(R.styleable.DropDownPreference_entries))
-  mEntryValues = a.getTextArray(R.styleable.DropDownPreference_entryValues)
+  setEntries(a.getTextArray(R.styleable.DropDownPreference_android_entries))
+  setEntryValues(a.getTextArray(R.styleable.DropDownPreference_android_entryValues))
   a.recycle
 
   protected override def getSummaryValue = getEntry
@@ -62,7 +64,7 @@ final class DropDownPreference(private val mContext: Context, attrs: AttributeSe
     * @see #setEntries(CharSequence[])
     * @param entriesResId The entries array as a resource.
     */
-  def setEntries(entriesResId: Int): Unit = setEntries(getContext.getResources.getTextArray(entriesResId))
+  def setEntries(@ArrayRes entriesResId: Int): Unit = setEntries(getContext.getResources.getTextArray(entriesResId))
   /**
     * The list of entries to be shown in the list in subsequent dialogs.
     *
@@ -82,7 +84,7 @@ final class DropDownPreference(private val mContext: Context, attrs: AttributeSe
     * @see #setEntryValues(CharSequence[])
     * @param entryValuesResId The entry values array as a resource.
     */
-  def setEntryValues(entryValuesResId: Int): Unit =
+  def setEntryValues(@ArrayRes entryValuesResId: Int): Unit =
     setEntryValues(getContext.getResources.getTextArray(entryValuesResId))
   /**
     * Returns the array of values to be saved for the preference.
@@ -91,40 +93,26 @@ final class DropDownPreference(private val mContext: Context, attrs: AttributeSe
     */
   def getEntryValues: Array[CharSequence] = mEntryValues
 
+  private def getValue(index: Int) = (if (mEntryValues == null) index else mEntryValues(index)).toString
   /**
     * Sets the value of the key. This should be one of the entries in [[getEntryValues]].
     *
     * @param value The value to set for the key.
     */
-  def setValue(value: String) {
-    val i = findIndexOfValue(value)
-    if (i > -1) setValueIndex(i)
-  }
+  def setValue(value: String): Unit = setValue(findIndexOfValue(value), value)
 
   /**
     * Sets the value to the given index from the entry values.
     *
-    * Remember to callChangeListener() if this extends Preference directly
-    *
-    * https://github.com/android/platform_frameworks_base/blob/
-    * 4535e11fb7010f2b104d3f8b3954407b9f330e0f/core/java/
-    * android/preference/ListPreference.java#L282
-    *
     * @param index The index of the value to set.
     */
-  def setValueIndex(index: Int) {
-    val changed = mSelectedIndex != index
-    if (changed || !mValueSet) {
-      mSelectedIndex = index
-      mValueSet = true
-      if (mEntryValues != null) {
-        val value = mEntryValues(index).toString
-        if (changed) callChangeListener(value)
-        persistString(value)
-      }
-      if (changed) notifyChanged
-    }
+  def setValueIndex(index: Int) = setValue(index, getValue(index))
+
+  private def setValue(index: Int, value: String) {
+    persistString(value)
+    mSelectedIndex = index
     mSpinner.setSelection(index)
+    notifyChanged
   }
 
   /**
diff --git a/src/main/scala/com/github/shadowsocks/preferences/NumberPickerPreference.scala b/src/main/scala/com/github/shadowsocks/preferences/NumberPickerPreference.scala
index ef93c9cc..afe29b74 100644
--- a/src/main/scala/com/github/shadowsocks/preferences/NumberPickerPreference.scala
+++ b/src/main/scala/com/github/shadowsocks/preferences/NumberPickerPreference.scala
@@ -28,7 +28,7 @@ final class NumberPickerPreference(context: Context, attrs: AttributeSet = null)
   def getMin = if (picker == null) 0 else picker.getMinValue
   def getMax = picker.getMaxValue
   def setValue(i: Int) {
-    if (i == getValue || !callChangeListener(i)) return
+    if (i == getValue) return
     picker.setValue(i)
     value = picker.getValue
     persistInt(value)
@@ -49,7 +49,10 @@ final class NumberPickerPreference(context: Context, attrs: AttributeSet = null)
   override protected def onDialogClosed(positiveResult: Boolean) {
     picker.clearFocus // commit changes
     super.onDialogClosed(positiveResult)  // forward compatibility
-    if (positiveResult) setValue(picker.getValue) else picker.setValue(value)
+    if (positiveResult) {
+      val value = picker.getValue
+      if (callChangeListener(value)) setValue(value)
+    } else picker.setValue(value)
   }
   override protected def onGetDefaultValue(a: TypedArray, index: Int) = a.getInt(index, getMin).asInstanceOf[AnyRef]
   override protected def onSetInitialValue(restorePersistedValue: Boolean, defaultValue: Any) {