[FIXED] How to use custom attr with selector in Android?

Issue

This is my custom attr:

<?xml version="1.0" encoding="utf-8"?>
<resources>    
    <declare-styleable name="MyComponent">
        <attr name="mycustom" format="boolean"/>
    </declare-styleable>
</resources>

This is how I use it in layout:

<com.edu.MyComponent
    style="@style/MyStyle"
    app:mycustom="true"/>

It works ok in MyComponent class because I get true from this call:

typedArray.getBoolean(R.styleable.MyComponent_mycustom, false);

However, it doesn't have any effect in selector:

<selector xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item app:mycustom="false">
        (...)
    </item>
    <item app:mycustom="true">
        (...)
    </item>
</selector>

What am I doing wrong?

EDIT:

The trick was to correctly use refreshDrawableState() + onCreateDrawableState(). As to using custom attribute in selectors additionally for child elements I had to also use this:

android:duplicateParentState="true"

Solution

Step 1: declare the custom state attribute

The custom state is declared in the ‘attrs.xml’ file in the application’s ‘res/values’ directory.

<?xml version="1.0" encoding="utf-8"?>
<resources>    
    <declare-styleable name="MyComponent">
        <attr name="mycustom" format="boolean"/>
    </declare-styleable>
</resources>

Step 2: use the custom state in the state list drawables

In the message list example there are two state list drawables.

One for the list item background:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:example="http://schemas.android.com/apk/res/com.charlesharley.example.android.customdrawablestates"
          >
    <!-- We make the pressed and focused selector items transparent so the ListView's own selector states show through. -->
    <item android:state_pressed="true"
          android:drawable="@android:color/transparent"
          />
    <item android:state_focused="true"
          android:drawable="@android:color/transparent"
          />
    <item example:state_message_unread="true"
          android:drawable="@color/message_list_item_background_unread"
          />
</selector>

And one for the message status icon:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:example="http://schemas.android.com/apk/res/com.charlesharley.example.android.customdrawablestates"
          android:constantSize="true"
          >
    <item example:state_message_unread="true"
          android:drawable="@drawable/message_read_status_unread"
          />
    <item android:drawable="@drawable/message_read_status_read" />
</selector>

Answered By - Aniket Jain
Answer Checked By - Robin (JavaFixing Admin)