To show an animation when starting or opening an activity on android, you can use this code.

First, you need create a folder named anim in res. see the screenshot

Then put your animation file in that anim folder. animation files are xml files that contains attributes of an animation.

if you don’t have an animation file, create a new animation file, right-click on that anim folder and select New > Animation Resource File. 

let’s name it My_Animation, then paste this code in the My_Animation file

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

    <!--suppress AndroidElementNotAllowed -->
    <objectAnimator
        android:duration="150"
        android:propertyName="x"
        android:valueFrom="-1280"
        android:valueTo="0"
        android:valueType="floatType" />
</set>

Now you have successfully created an animation file. next step is implementing this animation to an activity.

This code below sets the animation

Intent i = new Intent(ThisActivity.this, NewActivity.class);
               startActivity(i);// this is the code to start activity
              overridePendingTransition(R.anim.My_Animation, R.anim.My_Animation);//this code plays the animation

That is it, you now have animation when opening the activity.