How to create Drawable Animations in Android

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="com.example.application.animationexample.MainActivity">

    <ImageView
        android:id="@+id/image"
        android:layout_width="250dp"
        android:layout_height="250dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

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

    <item
        android:drawable="@drawable/ic_signal_1"
        android:duration="400" />

    <item
        android:drawable="@drawable/ic_signal_2"
        android:duration="400" />

    <item
        android:drawable="@drawable/ic_signal_3"
        android:duration="400" />

    <item
        android:drawable="@drawable/ic_signal_4"
        android:duration="400" />

    <item
        android:drawable="@drawable/ic_signal_5"
        android:duration="400" />

</animation-list>

package com.example.application.animationexample;

import android.graphics.drawable.AnimationDrawable;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {
    AnimationDrawable wifiAnimation;

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

        ImageView imageView = (ImageView) findViewById(R.id.image);
        imageView.setBackgroundResource(R.drawable.animation);
        wifiAnimation = (AnimationDrawable) imageView.getBackground();
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        wifiAnimation.start();
    }
}