[Android] Button background change for state. (selector)

color - bg_selector.xml

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

    <!-- Active tab -->
    <item android:drawable="@drawable/bg_selected" android:state_focused="false" android:state_pressed="false" android:state_selected="true"/>
    <!-- Inactive tab -->
    <item android:drawable="@drawable/bg_unselected" android:state_focused="false" android:state_pressed="false" android:state_selected="false"/>
    <!-- Pressed tab -->
    <item android:drawable="@drawable/bg_focused" android:state_pressed="true"/>
    <!-- Selected tab (using d-pad) -->
    <item android:drawable="@drawable/bg_focused" android:state_focused="true" android:state_pressed="false" android:state_selected="true"/>

</selector>

drawable - bg.xml

<!-- bg_focused.xml -->
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <corners android:radius="10dp" />

    <gradient
        android:centerColor="#5290c3"
        android:endColor="#6f9fc7"
        android:startColor="#78a4c9" />

</shape>

<!-- bg_selected.xml -->
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <corners android:radius="10dp" />

    <gradient
        android:centerColor="#72b0e3"
        android:endColor="#8fafe7"
        android:startColor="#98c4e9" />

</shape>

<!-- bg_unselected.xml -->
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <corners android:radius="10dp" />

    <gradient
        android:centerColor="#7ac19b"
        android:endColor="#588d71"
        android:startColor="#95ceae" />

</shape>

layout - activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/button1"
            android:layout_width="0dp"
            android:layout_height="48dp"
            android:layout_weight="1"
            android:background="@color/bg_selector"
            android:text="Now" />

        <Button
            android:id="@+id/button2"
            android:layout_width="0dp"
            android:layout_height="48dp"
            android:layout_weight="1"
            android:background="@color/bg_selector"
            android:text="Last" />

        <Button
            android:id="@+id/button3"
            android:layout_width="0dp"
            android:layout_height="48dp"
            android:layout_weight="1"
            android:background="@color/bg_selector"
            android:text="2mnt Ago" />
    </LinearLayout>

    <TextView
        android:id="@+id/text1"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:layout_weight="1"
        android:padding="@dimen/padding_medium"
        android:text="@string/hello_world"
        tools:context=".MainActivity" />

</LinearLayout>

MainActivity.java

package com.example.sellectorsample;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener {
    Button mButton1;
    Button mButton2;
    Button mButton3;
    TextView mText1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mButton1 = findViewByIdAndCast(R.id.button1);
        mButton2 = findViewByIdAndCast(R.id.button2);
        mButton3 = findViewByIdAndCast(R.id.button3);

        mText1 = findViewByIdAndCast(R.id.text1);

        mButton1.setOnClickListener(this);
        mButton2.setOnClickListener(this);
        mButton3.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        Button button = (Button) v;

//        mButton1.setBackgroundResource(R.color.bg_selector);
//        mButton2.setBackgroundResource(R.color.bg_selector);
//        mButton3.setBackgroundResource(R.color.bg_selector);
//        button.setBackgroundResource(R.drawable.bg_selected);

        // clear state
        mButton1.setSelected(false);
        mButton1.setPressed(false);
        mButton2.setSelected(false);
        mButton2.setPressed(false);
        mButton3.setSelected(false);
        mButton3.setPressed(false);

        // change state
        button.setSelected(true);
        button.setPressed(false);

        mText1.setText("select: " + button.getText());
    }

    @SuppressWarnings("unchecked")
    private <T> T findViewByIdAndCast(int id) {
        return (T) findViewById(id);
    }

}