create custom selector

attrs.xml

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

bg_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:app="http://schemas.android.com/apk/res-auto">

    <item app:state_foo_enabled="true">
        <color android:color="#F00"/>
    </item>

    <item>
        <color android:color="#00F"/>
    </item>
</selector>

main.xml

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

    <com.example.HelloAndroid.widget.MyTextView
        android:id="@+id/text1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:padding="20dp"
        android:background="@drawable/bg_selector"
        android:text="hello" />

    <com.example.HelloAndroid.widget.MyTextView
        android:id="@+id/text2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:padding="20dp"
        android:background="@drawable/bg_selector"
        android:text="hello" />


</LinearLayout>

MyActivity.java

package com.example.HelloAndroid;

import android.app.Activity;
import android.os.Bundle;
import com.example.HelloAndroid.widget.MyTextView;

public class MyActivity extends Activity {

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ((MyTextView) findViewById(R.id.text2)).setFoo(true);


    }


}

MyTextView.java

package com.example.HelloAndroid.widget;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.TextView;
import com.example.HelloAndroid.R;

/**
 * Created with IntelliJ IDEA.
 * User: dingzhihu
 * Date: 13-11-18
 * Time: 上午10:08
 */
public class MyTextView extends TextView {
    private static final int[] STATE_FOO_ENABLED = {
            R.attr.state_foo_enabled
    };

    private boolean isFoo;

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

    public void setFoo(boolean foo) {
        isFoo = foo;
        refreshDrawableState();
    }



    @Override
    protected int[] onCreateDrawableState(int extraSpace) {
        final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);
        if (isFoo) {
            mergeDrawableStates(drawableState, STATE_FOO_ENABLED);
        }
        return drawableState;
    }
}