ListPreference's summary text is not updated automatically whenever there is change in selection

Question

Although it is being documented, by using "%s" , I can display selected value as summary, it doesn't work as expected.

http://developer.android.com/reference/android/preference/ListPreference.html#getSummary%28%29

I am having the following preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory
        android:title="@string/preference_xxx_category">
        <CheckBoxPreference
            android:title="@string/preference_xxx_mode_title"
            android:defaultValue="false"
            android:summary="@string/preference_xxx_mode_summary"
            android:key="xxxModePreference" />
    </PreferenceCategory>

    <PreferenceCategory
        android:title="@string/preference_yyy_category">
        <ListPreference
           android:title="@string/preference_yyy_mode_title"
           android:defaultValue="0"
           android:entries="@array/yyy"
           android:entryValues="@array/yyy_values"
           android:summary="%s"
           android:key="yyyModePreference" />         
    </PreferenceCategory>

</PreferenceScreen>

and here is my arrays.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="yyy">
        <item>Display value 0</item>
        <item>Display value 1</item>
    </string-array>

    <string-array name="yyy_values">
        <item>0</item>
        <item>1</item>
    </string-array>    
</resources>

What I expecting by having the following Java code to build a complete preference activity, with a check box and a list preference, the summary text of list preference can be updated automatically, whenever I perform selection. The summary text will toggle in between Display value 0 and Display value 1 .

public class Preferences extends PreferenceActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }
}

However, I realize the summary text for list preference will not update automatically. Only when I perform tick/ untick on check box, only the whole activity will be invalidate and summary text for list preference will ONLY be updated.

Hence, I have to revise my code as follow, which looks more cumbersome .

public class Preferences extends PreferenceActivity implements OnSharedPreferenceChangeListener {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
        PreferenceManager.getDefaultSharedPreferences(this).registerOnSharedPreferenceChangeListener(this);
    }

    @Override
    public void onResume() {
        super.onResume();

        // Cumbersome way to make sure list preference's summary text is being updated.
        final String key = "yyyModePreference";
        ListPreference listPreference = (ListPreference)findPreference(key);
        final String value = PreferenceManager.getDefaultSharedPreferences(this).getString(key, key);
        final int index = listPreference.findIndexOfValue(value);
        if (index >= 0) {
            final String summary = (String)listPreference.getEntries()[index];         
            listPreference.setSummary(summary);
        }
    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences options, String key) {
        // Cumbersome way to make sure list preference's summary text is being updated.
        if (key.equals("yyyModePreference")) {
            ListPreference listPreference = (ListPreference)findPreference(key);
            final String value = options.getString(key, key);
            final int index = listPreference.findIndexOfValue(value);            
            if (index >= 0) {
                final String summary = (String)listPreference.getEntries()[index];         
                listPreference.setSummary(summary);
            }
        }
    }
}

Is this a correct way? Is there any simplified way, to ensure ListPreference's summary text is always updated automatically whenever there is change in selection.

Answer 1

This is a bug that existed on platforms prior to KITKAT (ie android-4.4_r0.7), and it is fixed by commit 94c02a1

The solution from @ilomambo works, but may not be the best one. I read through the source of ListPreference and came up with this solution:

File: ListPreferenceCompat.java

package com.example.yourapplication;

import android.content.Context;
import android.os.Build;
import android.preference.ListPreference;
import android.text.TextUtils;
import android.util.AttributeSet;

public class ListPreferenceCompat extends ListPreference {

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public ListPreferenceCompat(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public ListPreferenceCompat(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public ListPreferenceCompat(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ListPreferenceCompat(Context context) {
        super(context);
    }

    // NOTE:
    // The framework forgot to call notifyChanged() in setValue() on previous versions of android.
    // This bug has been fixed in android-4.4_r0.7.
    // Commit: platform/frameworks/base/+/94c02a1a1a6d7e6900e5a459e9cc699b9510e5a2
    // Time: Tue Jul 23 14:43:37 2013 -0700
    //
    // However on previous versions, we have to work around it by ourselves.
    @Override
    public void setValue(String value) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            super.setValue(value);
        } else {
            String oldValue = getValue();
            super.setValue(value);
            if (!TextUtils.equals(value, oldValue)) {
                notifyChanged();
            }
        }
    }
}

When you need to use ListPreference in xml, simply replace the tag to com.example.yourapplication.ListPreferenceCompat .

This works neatly on my Samsung S4 device running Android 4.3, and inside one of my production app.

Answer 2

I guess its some kind of a weird bug, because I've tested it on emulator running Android 2.3.3 and it didn't work, but when i tested it on 4.0.3 it worked. What i did was android:summary="%s" in xml for ListPreference and that's all.

Answer 3

IMHO it is a bug. The onClickListener() defined in ListPreference.java#builder.setSingleChoiceItems() does not call notifyChanged()

I happen to be coding my own ListPreference based on that code, and ran across the same problem as the OP, I added notifyChanged() :

            ...
            dialog.dismiss();
            notifyChanged(); // <<<<<<<<<<
        }
});

and now the preference summary is updated as soon as I choose it. It is not dependent on the Android version, ListPreference has been coded like this since ever.