The summary field of PreferenceCategory tag

Question

I have seen something like this:

<PreferenceCategory xmlns:android="http://schemas.android.com/apk/res/android"
    android:key="vegi_category" android:title="Vegetables"

    android:summary="Preferences related to vegetable">  <!-- Why is this here? -->

    <CheckBoxPreference android:key="tomato_selection_pref"
        android:title="Tomato " android:summary="It's actually a fruit" />
    <CheckBoxPreference android:key="potato_selection_pref"
        android:title="Potato" android:summary="My favorite vegetable" />
</PreferenceCategory>

But I do not get it why is there a summary field for the pref category:

(android:summary="Preferences related to vegetable") ?

When I use pref screen the summary is presented in the view, but this is not a case with pref category. Is the existence of summary in pref category just a convention of it can be seen somehow ?

What is the actual usage of summary in pref category element ?

Emulsoid

Answer 1

The standard PreferenceCategory widget shows only the title; the android:summary attribute is ignored.

That's because the default layout (preference_category.xml) contains only a single TextView for the title field:

<!-- Layout used for PreferenceCategory in a PreferenceActivity. -->
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    style="?android:attr/listSeparatorTextViewStyle"
    android:id="@+android:id/title"
/>

If you want to show the summary as well, you can specify your own layout using the android:layout attribute. For example:

<PreferenceCategory android:title="Category" android:summary="This is the summary"
                    android:layout="@layout/preference_category_summary">

Where layout/preference_category_summary.xml is something like:

<!-- Layout used for PreferenceCategory + SUMMARY in a PreferenceActivity. -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent" android:layout_height="wrap_content"
              android:orientation="vertical">
    <TextView android:id="@+android:id/title" 
              style="?android:attr/listSeparatorTextViewStyle"/>
    <TextView android:id="@+android:id/summary"
              android:paddingLeft="5dip" android:paddingRight="dip"
              android:layout_width="match_parent" android:layout_height="wrap_content"/>
</LinearLayout>

Before you go ahead and do this, however, you should consider whether it's less or more confusing to the user. Unless you style the summary text carefully, it will either jump out of the screen or appear to attach to the first preference in the category.

Ascertain

Answer 2

You could just use Preference and android:summary.

<PreferenceCategory xmlns:android="http://schemas.android.com/apk/res/android"
    android:key="vegi_category" android:title="Vegetables">

    <Preference android:summary="Preferences related to vegetable" />

    <CheckBoxPreference android:key="tomato_selection_pref"
        android:title="Tomato " android:summary="It's actually a fruit" />
    <CheckBoxPreference android:key="potato_selection_pref"
        android:title="Potato" android:summary="My favorite vegetable" />
</PreferenceCategory>

Marbles

I find that this works very well (as compared to changing the layout; since it needs to match the Android version look and feel too). Additionally if you add android:selectable=false you can achieve the similar look and feel. – Plumbing

Answer 3

@ehartwell is absolutely right
my layouts for diff versions are:

for pre-lollipop

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

  <TextView android:id="@android:id/title"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="6dp"
    android:textSize="14sp"
    android:textStyle="bold"
    android:textAllCaps="true"
    android:paddingLeft="8dp"
    android:paddingRight="8dp"/>

  <TextView android:id="@android:id/summary"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="-5dp"
    android:textSize="12sp"
    style="?android:attr/listSeparatorTextViewStyle"/>

</LinearLayout>

for post-lollipop

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingLeft="@dimen/preference_category_margin"
    android:paddingRight="@dimen/preference_category_margin"
    android:orientation="vertical">

  <TextView android:id="@android:id/title"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="6dp"
    android:textStyle="bold"
    android:textSize="13sp"
    android:textAllCaps="false"
    android:textColor="@color/colorAccent"/>

  <TextView android:id="@android:id/summary"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textSize="12sp"
    android:textColor="@color/colorAccent"
    android:textAllCaps="false"/>

</LinearLayout>

@dimen/preference_category_margin is diff for special screen size
16dp or 24dp
and they are pretty well:)

Lissome