Android animation

Topics
• Frame by Frame animation
• Tween animation
> Translate, Rotate, Scale, Alpha
• Interpolator
• Layout animation

What is Frame-by-Frame Animation?
• Created with a sequence of different images,
played in order, like a roll of film.
• Pieces
> The frames in the /res/drawable directory
> Animation resource XML file in which the frames
are specified as <item> under <animation-list>
> Code that loads the Animation resource XML file

Animation XML Resource
• The XML file consists of an <animation-list>
element as the root node and a series of child
<item> nodes that each define a frame
<?xml version="1.0" encoding="UTF-8"?>
<animation-list
xmlns:android="http://schemas.android.com/apk/res/android"
id="selected" android:oneshot="false">
<item android:drawable="@drawable/ball1" android:duration="50" />
</animation-list>

Code That Starts the Animation
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.framebyframe);
// Load the ImageView that will host the animation and
// set its background to the AnimationDrawable XML resource.
ImageView img = (ImageView) findViewById(R.id.my_image_view);
img.setBackgroundResource(R.anim.simple_animation);
// Get the background, which has been compiled to an AnimationDrawable object.
frameAnimation = (AnimationDrawable) img.getBackground();
}
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
if (animationStarted){
frameAnimation.stop();
animationStarted = false;
}
else{
frameAnimation.start();
animationStarted = true;
}
return true;
}
return super.onTouchEvent(event);

Built-in Tween Animation Schemes
• TransitionAnimation
> Position change
• RotateAnimation
> Rotation
• ScaleAnimation
> Scaling
• AlphaAnimation
> Transparancy

Steps of Tween Animation
• Create XML animation resource file in
/res/anim/ directory
• Load the XML animation resource file into
Animation object
• Start the animation

Create Animation XML Resource
• The XML file is located under /res/anim/ directory
• Example below is for Rotate animation
<?xml version="1.0" encoding="UTF-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:interpolator="@android:anim/accelerate_decelerate_interpolator"
android:fromDegrees="0"
android:toDegrees="270"
android:toYScale="0.0"
android:pivotX="50%"
android:pivotY="50%"
android:startOffset="700"
android:duration="700" />

Create Animation XML Resource
• Sequential animation is done with <set>
• Example below - Translate animation followed by
Rotate animation
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:shareInterpolator="false">
<translate
android:fromXDelta="0"
android:toXDelta="100"
android:fromYDelta="0"
android:toYDelta="150"
<rotate
android:interpolator="@android:anim/accelerate_decelerate_interpolator"
android:fromDegrees="0"
android:toDegrees="270"
android:toYScale="0.0"
android:pivotX="50%"
android:pivotY="50%"
android:startOffset="700"
</set>

Loading Animation Resource &
Staring Animation
// Load Animation object from a resource
Animation rotate = AnimationUtils.loadAnimation(this,
R.anim.rotate);
// Select the animation target and start the animation
findViewById(R.id.myimage).startAnimation(rotate);

What is Interpolator
• An interpolator defines the rate of change of an
animation.
• This allows the basic animation effects (alpha,
scale, translate, rotate) to be accelerated,
decelerated, repeated, etc.
• You can set an interpolator either in XML
animation resource file or programmatically

Built-in Android Interpolators
• Built-in Android Interpolators
> android.R.anim.accelerate_interpolator
> android.R.anim.decelerate_interpolator
> android.R.anim.accelerate_decelerate_interpolator
> android.R.anim.anticipate_interpolator
> android.R.anim.overshoot_interpolator
• Example of setting interpolator programmatically
mAnimation.setInterpolator( AnimationUtils.loadInterpolator(this,
android.R.anim.accelerate_interpolator));

What is Layout Animation?
• Animations are applied when components are
laid out
> When components are added or removed from
layouts, these animations are triggered.

Steps for Layout Animation
1.Create “layout animation” resource files
under /res/anim/ directory
2.Add android:layoutAnimation=@anim/<layout-
animation-resource-file> attribute to the layout
3.Load the layout resource file as you normally
do

1. Create Animation XML Resources
• Create it under /res/anim/ directory - let's call it
/res/anim/layout_bottom_to_top_slide.xml
<?xml version="1.0" encoding="utf-8"?>
<layoutAnimation
xmlns:android="http://schemas.android.com/apk/res/android"
android:delay="500%"
android:animationOrder="reverse"
android:animation="@anim/slide_right" />
• The above uses /res/anim/slide_right.xml below
<set xmlns:android="http://schemas.android.com/apk/res/android"
android:interpolator="@android:anim/accelerate_interpolator">
<translate android:fromXDelta="-100%p" android:toXDelta="0"
android:duration="@android:integer/config_shortAnimTime" />
</set>

2. Create Layout Resource File
• Layout resource file now has
android:layoutAnimation attribute
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layoutAnimation="@anim/layout_bottom_to_top_slide" />

3. Load Layout resource
• There is nothing different in this code
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_animation_3);
setListAdapter(new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, mStrings));
}

Android animation

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