Android Working with NumerPicker

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="ir.mhdr.a070.MainActivity">

    <NumberPicker
        android:id="@+id/numberPicker2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="166dp" />
</RelativeLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    NumberPicker numberPicker;

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

        numberPicker= (NumberPicker) findViewById(R.id.numberPicker2);
        numberPicker.setMaxValue(99);
        numberPicker.setMinValue(0);
        numberPicker.setValue(25);
        numberPicker.setDescendantFocusability(NumberPicker.FOCUS_BLOCK_DESCENDANTS);
    }
}

References
https://github.com/mhdr/AndroidSamples/tree/master/070