Android Working with XML Animations
Adding animations to your app interface will give high quality feel to your android applications. Animations can be performed through either XML or android code. In this tutorial i explained how to do animations using XML notations. I will explain how to do the same using android java code in future tutorials. Here i covered basic android animations like fade in, fade out, scale, rotate, slide up, slide down etc.,
In the source code project provided in this tutorial, I wrote separate activity and XML for each animation. Download and play with the code to get familiar with the animations. Following are list of animations covered in this article.
Basic steps to perform animation
Following are the basic steps to perform an animation on any UI element. Creating animation is very simple, all it needs is creating necessary files and write small pieces of code.
Step 1: Create xml that defines the animation
Create an xml file which defines type of animation to perform. This file should be located under anim folder under res directory (res ⇒ anim ⇒ animation.xml). If you don’t have anim folder in your res directory create one. Following is example of simple fade in animation.
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true" >
<alpha
android:duration="1000"
android:fromAlpha="0.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:toAlpha="1.0" />
</set>
Step 2: Load the animation
Next in your activity create an object of Animation class. And load the xml animation using AnimationUtils by calling loadAnimation function.
public class FadeInActivity extends Activity{
TextView txtMessage;
// Animation
Animation animFadein;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fadein);
txtMessage = (TextView) findViewById(R.id.txtMessage);
// load the animation
animFadein = AnimationUtils.loadAnimation(getApplicationContext(),
R.anim.fade_in);
}
}
Step 3: Set the animation listeners (Optional)
If you want to listen to animation events like start, end and repeat, your activity should implements AnimationListener. This step is optional. If you implement AnimationListener you will have to override following methods.
onAnimationStart – This will be triggered once the animation started
onAnimationEnd – This will be triggered once the animation is over
onAnimationRepeat – This will be triggered if the animation repeats
public class FadeInActivity extends Activity implements AnimationListener {
.
.
.
// set animation listener
animFadein.setAnimationListener(this);
.
.
.
// animation listeners
@Override
public void onAnimationEnd(Animation animation) {
// Take any action after completing the animation
// check for fade in animation
if (animation == animFadein) {
Toast.makeText(getApplicationContext(), "Animation Stopped",
Toast.LENGTH_SHORT).show();
}
}
@Override
public void onAnimationRepeat(Animation animation) {
// Animation is repeating
}
@Override
public void onAnimationStart(Animation animation) {
// Animation started
}
Step 4: Finally start the animation
You can start animation whenever you want by calling startAnimation on any UI element by passing the type of animation. In this example i am calling fade in animation on TextView.
// start the animation txtMessage.startAnimation(animFadein);
Complete Code
Following is complete code for FadeInActivity
package info.androidhive.androidanimations;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.animation.Animation.AnimationListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class FadeInActivity extends Activity implements AnimationListener {
TextView txtMessage;
Button btnStart;
// Animation
Animation animFadein;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fadein);
txtMessage = (TextView) findViewById(R.id.txtMessage);
btnStart = (Button) findViewById(R.id.btnStart);
// load the animation
animFadein = AnimationUtils.loadAnimation(getApplicationContext(),
R.anim.fade_in);
// set animation listener
animFadein.setAnimationListener(this);
// button click event
btnStart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
txtMessage.setVisibility(View.VISIBLE);
// start the animation
txtMessage.startAnimation(animFadein);
}
});
}
@Override
public void onAnimationEnd(Animation animation) {
// Take any action after completing the animation
// check for fade in animation
if (animation == animFadein) {
Toast.makeText(getApplicationContext(), "Animation Stopped",
Toast.LENGTH_SHORT).show();
}
}
@Override
public void onAnimationRepeat(Animation animation) {
// TODO Auto-generated method stub
}
@Override
public void onAnimationStart(Animation animation) {
// TODO Auto-generated method stub
}
}
Important XML animation attributes
When working with animations it is better to have through knowledge about some of the important XML attributes which create major differentiation in animation behavior. Following are the important attributes you must known about.
android:duration – Duration of the animation in which the animation should complete
android:startOffset – It is the waiting time before an animation starts. This property is mainly used to perform multiple animations in a sequential manner
android:interpolator – It is the rate of change in animation
android:fillAfter – This defines whether to apply the animation transformation after the animation completes or not. If it sets to false the element changes to its previous state after the animation. This attribute should be use with <set> node
android:repeatMode – This is useful when you want your animation to be repeat
android:repeatCount – This defines number of repetitions on animation. If you set this value to infinite then animation will repeat infinite times
Some useful animations
Following i am giving xml code to perform lot of useful animations. Try to assign different values to xml attributes to see change in animations.
1. Fade In
2. Fade Out
3. Cross Fading
4. Blink
5. Zoom In
6. Zoom Out
7. Rotate
8. Move
9. Slide Up
10. Slide Down
11. Bounce
12. Sequential Animation
13. Together Animation
Fade In
For fade in animation you can use <alpha> tag which defines alpha value. Fade in animation is nothing but increasing alpha value from 0 to 1.
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true" >
<alpha
android:duration="1000"
android:fromAlpha="0.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:toAlpha="1.0" />
</set>
Fade Out
Fade out is exactly opposite to fade in, where we need to decrease the alpha value from 1 to 0
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true" >
<alpha
android:duration="1000"
android:fromAlpha="1.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:toAlpha="0.0" />
</set>
Cross Fading
Cross fading is performing fade in animation while other element is fading out. For this you don’t have to create separate animation file, you can just use fade_in.xml and fade_out.xml files.
In the following code i loaded fade in and fade out, then performed them on two different UI elements.
TextView txtView1, txtView2; Animation animFadeIn, animFadeOut; . . // load animations animFadeIn = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_in); animFadeOut = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_out); . . // set animation listeners animFadeIn.setAnimationListener(this); animFadeOut.setAnimationListener(this); . . // Make fade in elements Visible first txtMessage2.setVisibility(View.VISIBLE); // start fade in animation txtMessage2.startAnimation(animFadeIn); // start fade out animation txtMessage1.startAnimation(animFadeOut);
Blink
Blink animation is animating fade out or fade in animation in repetitive fashion. For this you will have to set android:repeatMode=”reverse” and android:repeatCount attributes.
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<alpha android:fromAlpha="0.0"
android:toAlpha="1.0"
android:interpolator="@android:anim/accelerate_interpolator"
android:duration="600"
android:repeatMode="reverse"
android:repeatCount="infinite"/>
</set>
Zoom In
For zoom use <scale> tag. Use pivotX=”50%” and pivotY=”50%” to perform zoom from the center of the element. Also you need to use fromXScale, fromYScale attributes which defines scaling of the object. Keep these value lesser than toXScale, toYScale
<?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="3"
android:toYScale="3" >
</scale>
</set>
Zoom Out
Zoom out animation is same as zoom in but toXScale, toYScale values are lesser than fromXScale, fromYScale
<?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>
Rotate
Rotate animation uses <rotate> tag. For rotate animation required tags are android:fromDegrees and android:toDegrees which defines rotation angles.
Clock wise – use positive toDegrees value
Anti clock wise – use negative toDegrees value
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<rotate android:fromDegrees="0"
android:toDegrees="360"
android:pivotX="50%"
android:pivotY="50%"
android:duration="600"
android:repeatMode="restart"
android:repeatCount="infinite"
android:interpolator="@android:anim/cycle_interpolator"/>
</set>
Move
In order to change position of object use <translate> tag. It uses fromXDelta, fromYDelta for X-direction and toXDelta, toYDelta attributes for Y-direction.
<?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:fromXDelta="0%p"
android:toXDelta="75%p"
android:duration="800" />
</set>
Slide Up
Sliding animation uses <scale> tag only. Slide up can be achieved by setting android:fromYScale=”1.0″ and android:toYScale=”0.0″
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true" >
<scale
android:duration="500"
android:fromXScale="1.0"
android:fromYScale="1.0"
android:interpolator="@android:anim/linear_interpolator"
android:toXScale="1.0"
android:toYScale="0.0" />
</set>
Slide Down
Slide down is exactly opposite to slide down animation. Just interchange android:fromYScale and android:toYScale values.
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true">
<scale
android:duration="500"
android:fromXScale="1.0"
android:fromYScale="0.0"
android:interpolator="@android:anim/linear_interpolator"
android:toXScale="1.0"
android:toYScale="1.0" />
</set>
Bounce
Bounce is just an animation effect where animation ends in bouncing fashion. For this set android:interpolator value to @android:anim/bounce_interpolator. This bounce can be used with any kind animation. Following slide down example uses bounce effect.
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true"
android:interpolator="@android:anim/bounce_interpolator">
<scale
android:duration="500"
android:fromXScale="1.0"
android:fromYScale="0.0"
android:toXScale="1.0"
android:toYScale="1.0" />
</set>
Sequential Animation
If you want to perform multiple animation in a sequential manner you have to use android:startOffset to give start delay time. The easy way to calculate this value is to add the duration and startOffset values of previous animation. Following is a sequential animation where set of move animations performs in sequential manner.
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true"
android:interpolator="@android:anim/linear_interpolator" >
<!-- Use startOffset to give delay between animations -->
<!-- Move -->
<translate
android:duration="800"
android:fillAfter="true"
android:fromXDelta="0%p"
android:startOffset="300"
android:toXDelta="75%p" />
<translate
android:duration="800"
android:fillAfter="true"
android:fromYDelta="0%p"
android:startOffset="1100"
android:toYDelta="70%p" />
<translate
android:duration="800"
android:fillAfter="true"
android:fromXDelta="0%p"
android:startOffset="1900"
android:toXDelta="-75%p" />
<translate
android:duration="800"
android:fillAfter="true"
android:fromYDelta="0%p"
android:startOffset="2700"
android:toYDelta="-70%p" />
<!-- Rotate 360 degrees -->
<rotate
android:duration="1000"
android:fromDegrees="0"
android:interpolator="@android:anim/cycle_interpolator"
android:pivotX="50%"
android:pivotY="50%"
android:startOffset="3800"
android:repeatCount="infinite"
android:repeatMode="restart"
android:toDegrees="360" />
</set>
Together Animation
Performing all animation together is just writing all animations one by one without using android:startOffset
<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:fillAfter="true"
android:interpolator="@android:anim/linear_interpolator" >
<scale
xmlns:android="http://schemas.android.com/apk/res/android"
android:duration="4000"
android:fromXScale="1"
android:fromYScale="1"
android:pivotX="50%"
android:pivotY="50%"
android:toXScale="4"
android:toYScale="4" >
</scale>
<!-- Rotate 180 degrees -->
<rotate
android:duration="500"
android:fromDegrees="0"
android:pivotX="50%"
android:pivotY="50%"
android:repeatCount="infinite"
android:repeatMode="restart"
android:toDegrees="360" />
</set>
I hope you like this tutorial, feel free to ask any kind of questions in the comment section.
Thank You