Android Animations in Kotlin

Animation is a method in which a collection of images are combined in a specific way and processed then they appear as moving images. Building animations make on-screen objects seem to be alive. Android has quite a few tools to help you create animations with relative ease. so in this article we will learn to create animations using Kotlin. below are some attributes which we are using while writing the code in xml.

Table of Attributes :

XML ATTRIBUTES	DESCRIPTION
android:duration	It is used to specify the duration of animation to run
android:fromAlpha	It is the starting alpha value for the animation,  where 1.0 means fully opaque and 0.0 means fully transparent
android:toAlpha	It is the ending alpha value
android:id	Sets unique id of the view
android:fromYDelta	It is the change in Y coordinate to be applied at the start of the animation
android:toYDelta	It is the change in Y coordinate to be applied at the end of the animation
android:startOffset	Delay occur when an animation runs (in milliseconds), once start time is reached.
android:pivotX	It represents the X-axis coordinates to zoom from starting point.
android:pivotY	It represents the Y-axis coordinates to zoom from starting point.
android:fromXScale	Starting X size offset,
android:fromYScale	Starting Y size offset,
android:toXScale	Ending of X size offset
android:toYScale	Ending of Y size offset
android:fromDegrees	Starting angular position, in degrees.
android:toDegrees	Ending angular position, in degrees.
android:interpolator	An interpolator defines the rate of change of an animation

At first, we will create a new android application. Then, we will create some animations. 
If you already created the project then ignore step 1. 

Create New Project

1. Open Android Studio
2. Go to File => New => New Project.
3. Then, select Empty Activity and click on next
   • Write application name as DynamicEditTextKotlin
   • Select minimum SDK as you need, here we have selected 21 as minimum SDK
   • Choose language as Kotlin and click on finish button.

If you have followed above process correctly, you will get a newly created project successfully.
After creating project we will modify xml files. In xml file we will create one TextView where all the animations are performed and Eight Buttons for Eight different animations. 

Modify activity_main.xml file

Open res/layout/activity_main.xml file and add code into it. 

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/linearLayout"
        android:gravity="center"
        android:text="Geeks for Geeks"
        android:textSize="32sp"
        android:textColor="@color/colorPrimaryDark"
        android:textStyle="bold" />
    <LinearLayout
        android:id="@+id/linearLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:orientation="vertical">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:weightSum="2">
            <Button
                android:id="@+id/fade_in"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Fade In"
                android:textAllCaps="false" />
            <Button
                android:id="@+id/fade_out"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Fade Out"
                android:textAllCaps="false" />
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:weightSum="2">
            <Button
                android:id="@+id/zoom_in"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Zoom In"
                android:textAllCaps="false" />
            <Button
                android:id="@+id/zoom_out"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Zoom Out"
                android:textAllCaps="false" />
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:weightSum="2">
            <Button
                android:id="@+id/slide_down"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Slide Down"
                android:textAllCaps="false" />
            <Button
                android:id="@+id/slide_up"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Slide Up"
                android:textAllCaps="false" />
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:weightSum="2">
            <Button
                android:id="@+id/bounce"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Bounce"
                android:textAllCaps="false" />
            <Button
                android:id="@+id/rotate"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:text="Rotate"
                android:textAllCaps="false" />
        </LinearLayout>
    </LinearLayout>
</RelativeLayout>

After modifying the layout we will create xml files for animations. so we will first create a folder name anim.
In this folder, we will be adding the XML files which will be used to produce the animations. For this to happen, go to app/res right click and then select, Android Resource Directory and name it as anim.

bounce.xml

In this animation the text is bounce like a ball.  

XML

<?xml version="1.0" encoding="utf-8"?>
<set
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/linear_interpolator"
    android:fillAfter="true">
    <translate
        android:fromYDelta="100%"
        android:toYDelta="-20%"
        android:duration="300" />
    <translate
        android:startOffset="500"
        android:fromYDelta="-20%"
        android:toYDelta="10%"
        android:duration="150" />
    <translate
        android:startOffset="1000"
        android:fromYDelta="10%"
        android:toYDelta="0"
        android:duration="100" />
</set>

fade_in.xml

In Fade In animation the text will appear from background. 

XML

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/linear_interpolator">
    <alpha
        android:duration="1000"
        android:fromAlpha="0.1"
        android:toAlpha="1.0" />
</set>

fade_out.xml

In Fade Out animation the colour of text is faded for a particular amount of time. 

XML

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/linear_interpolator">
    <alpha
        android:duration="1000"
        android:fromAlpha="1.0"
        android:toAlpha="0.1" />
</set>

rotate.xml

In rotate animation the text is rotated for a particular amount of time. 

XML

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
    android:duration="1000"
    android:fromDegrees="0"
    android:interpolator="@android:anim/linear_interpolator"
    android:pivotX="50%"
    android:pivotY="50%"
    android:startOffset="0"
    android:toDegrees="360" />

slide_down.xml

In this animation the text will come from top to bottom. 

XML

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="1000"
        android:fromYDelta="-100%"
        android:toYDelta="0" />
</set>

slide_up.xml

In this animation the text will go from bottom to top. 

XML

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="1000"
        android:fromYDelta="0"
        android:toYDelta="-100%" />
</set>

zoom_in.xml

In this animation the text will appear bigger for a particular amount of time. 

XML

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:fillAfter="true">
    <scale xmlns:android="http://schemas.android.com/apk/res/android"
        android:duration="1000"
        android:fromXScale="1"
        android:fromYScale="1"
        android:pivotX="50%"
        android:pivotY="50%"
        android:toXScale="1.5"
        android:toYScale="1.5">
    </scale>
</set>

zoom_out.xml

In this animation the text will appear smaller for a particular amount of time. 

XML

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:fillAfter="true" >
    <scale
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:duration="1000"
        android:fromXScale="1.0"
        android:fromYScale="1.0"
        android:pivotX="50%"
        android:pivotY="50%"
        android:toXScale="0.5"
        android:toYScale="0.5" >
    </scale>
</set>

After creating all animations in xml. we will create MainActivity. 

Create MainActivity.kt file

Open app/src/main/java/net.geeksforgeeks.AnimationsInKotlin/MainActivity.kt file and add below code into it. 

Kotlin

package net.geeksforgeeks.animationsinkotlin

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Handler
import android.view.View
import android.view.animation.AnimationUtils
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        fade_in.setOnClickListener {
            textView.visibility = View.VISIBLE
            val animationFadeIn = AnimationUtils.loadAnimation(this, R.anim.fade_in)
            textView.startAnimation(animationFadeIn)
        }
        fade_out.setOnClickListener {
            val animationFadeOut = AnimationUtils.loadAnimation(this, R.anim.fade_out)
            textView.startAnimation(animationFadeOut)
            Handler().postDelayed({
                textView.visibility = View.GONE
            }, 1000)
        }
        zoom_in.setOnClickListener {
            val animationZoomIn = AnimationUtils.loadAnimation(this, R.anim.zoom_in)
            textView.startAnimation(animationZoomIn)
        }
        zoom_out.setOnClickListener {
            val animationZoomOut = AnimationUtils.loadAnimation(this, R.anim.zoom_out)
            textView.startAnimation(animationZoomOut)
        }
        slide_down.setOnClickListener {
            val animationSlideDown = AnimationUtils.loadAnimation(this, R.anim.slide_in)
            textView.startAnimation(animationSlideDown)
        }
        slide_up.setOnClickListener {
            val animationSlideUp = AnimationUtils.loadAnimation(this, R.anim.slide_out)
            textView.startAnimation(animationSlideUp)
        }
        bounce.setOnClickListener {
            val animationBounce = AnimationUtils.loadAnimation(this, R.anim.bounce)
            textView.startAnimation(animationBounce)
        }
        rotate.setOnClickListener {
            val animationRotate = AnimationUtils.loadAnimation(this, R.anim.rotate)
            textView.startAnimation(animationRotate)
        }
    }
}

As, AndroidManifest.xml file is very important file in android application, so below is the code of manifest file. 

AndroidManifest.xml file 

Code inside src/main/AndroidManifest.xml file would look like below

XML

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="net.geeksforgeeks.animationsinkotlin">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Run as Emulator:

You can find the complete code here: https://github.com/missyadavmanisha/AnimationsInKotlin