Develop Reference

Animate selector/state transitions

I have a simple selector for my ListView
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#drawable/yellow_arc" android:state_activated="true"/>
<item android:drawable="#drawable/yellow_nonarc" android:state_activated="false"/>
</selector>
I want to animate the transition between these drawables when the state of the views are changed from activated to not-activated and vica versa.
If you run the example in API demos you will see an obvious fade-in/fade-out animation while the activated state of the view is changed.
So what I want is a custom animation while the state of the view is changed. I think it should be done via xml but I couldn't find a way.
Thanks in advance.
EDIT:
I guess I have found something useful there's a activated_background.xml in \Android\android-sdk\platforms\android-API_VERSION\data\res\drawable which includes
<selector xmlns:android="http://schemas.android.com/apk/res/android"
android:exitFadeDuration="#android:integer/config_mediumAnimTime">
<item android:state_activated="true" android:drawable="#android:drawable/list_selector_background_selected" />
<item android:drawable="#color/transparent" />
</selector>
So the example in API-demos achieveing this fade-out animation by declaring an exitFadeDuration. However, this is not exactly what I want.. I want to declare custom animations for the transition between the state drawables since the fade-in/fade-out animation does not look good for my drawables.

Added in api 21 "StateListAnimator"
http://developer.android.com/reference/android/animation/StateListAnimator.html
I know this is an old question but this may help future people looking to do this.

I guess TransitionDrawable could help you to accomplish this.
You can check the answer here:
Animate change of view background color on Android

The modern way (since api 21) of doing it with example:
<?xml version="1.0" encoding="utf-8"?>
<animated-selector xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
android:id="#+id/checked"
android:drawable="#drawable/check_box_on"
app:check="true" /> <!-- this is custom state. You can use android:state_checked="true"-->
<item
android:id="#+id/unchecked"
android:drawable="#drawable/check_box_off"
app:check="false" />
<transition
android:drawable="#drawable/toggle_checkbox_unchecked_checked"
android:fromId="#+id/unchecked"
android:toId="#+id/checked" />
<transition
android:drawable="#drawable/toggle_checkbox_checked_unchecked"
android:fromId="#+id/checked"
android:toId="#+id/unchecked" />
</animated-selector>
documentation for animated-selector: link
where transition drawable is for example this:
<?xml version="1.0" encoding="utf-8"?>
<animated-vector xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:aapt="http://schemas.android.com/aapt"
android:drawable="#drawable/check_box_on">
<target android:name="check_box_on_path">
<aapt:attr name="android:animation">
<objectAnimator
android:duration="#android:integer/config_shortAnimTime"
android:interpolator="#android:interpolator/decelerate_cubic"
android:propertyName="trimPathEnd"
android:valueFrom="1"
android:valueTo="0"
android:valueType="floatType" />
</aapt:attr>
</target>
</animated-vector>
documentation for animated-vector: link

Is it the fade you want?
I guess it would be the same as how a textSwitcher works, maybe you want to change it to a ViewSwitcher instead, the fade is done pro-grammatically
Animation in = AnimationUtils.loadAnimation(this,
android.R.anim.fade_in);
Animation out = AnimationUtils.loadAnimation(this,
android.R.anim.fade_out);
mSwitcher1.setInAnimation(in);
mSwitcher1.setOutAnimation(out);

animation-list not animating initially

I have a checkbox that should look like a green light when checked and a red blinking light when unchecked. To do this I created a selector called connected_selector.xml.
<?xml version="1.0" encoding="utf-8"?>
<selector
xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="true" android:drawable="#drawable/green_button" />
<item android:state_checked="false" android:drawable="#drawable/red_button_blinking" />
<item android:drawable="#drawable/red_button_blinking" />
</selector>
The green_button is simply a png and the red_button_blinking is an animation-list of pngs.
<?xml version="1.0" encoding="utf-8"?>
<animation-list
xmlns:android="http://schemas.android.com/apk/res/android" android:oneshot="false">
<item android:drawable="#drawable/red_button" android:duration="500" />
<item android:drawable="#drawable/red_button_lit" android:duration="500" />
</animation-list>
The checkbox's background is set to #drawable/connected_selector. If the checkbox is initially unchecked, it doesn't blink, it just shows the #drawable/red_button. However if I check the box and then uncheck it, the checkbox will animate correctly.
How can I make the animation start initially since the checkbox will be initially unchecked? I guess I could try to start the animation manually in code, but I don't think that should be necessary.

Okay, I found an ugly, dirty hack to get around this. Note that I don't have the slightest clue why this happens, just a way around this. It is probably not even a generic way since different devices will have different loading times.
I execute the following workaround in onPostResume() to minimize the necessary delay time.
if(onOffStatus) {
// SLEEP 0.5 SECONDS HERE ...
new Handler().postDelayed(new Runnable() {
public void run() {
switcher.setBackgroundResource(R.drawable.button_state_anim);
// Get the background, which has been compiled to an AnimationDrawable object.
AnimationDrawable frameAnimation = (AnimationDrawable) switcher.getBackground();
// Start the animation (looped playback by default).
frameAnimation.start();
}
}, 500); // Actual required time will probably be dependent on device performance
}
It ain't pretty but I'm going with this until I find something better. Let me know if I overlooked something here.

Button Background Selector

I try to switch the background of Buttons if they are pressed. I build a Selector like the answer suggested here: Standard Android Button with a different color
Finally I want to put GradientDrawables inside, but for debugging purposes I just set a color, to check if it works.
Here is my Selector
<?xml version="1.0" encoding="utf-8"?>
<selector
xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#color/red"/>
<item
android:state_focused="true"
android:drawable="#color/white"/>
<item
android:state_pressed="true"
android:drawable="#color/white"/>
</selector>
Unfortunatly this doesn't work. I set the Selector as Button background and only see them in red color. What Am I doing wrong (Build Target 2.1)

put this at the end
item android:drawable="#color/red"
i mean as the third option, it will work.
android checks the xml conditions from the start, the first tag doesn't have any condition, so it will always pick red, so you have put conditions first and then the default one.

here is the code I use, and it works really well.
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#drawable/button_clicked"
android:state_pressed="true" android:state_enabled="true" />
<item android:drawable="#drawable/button" android:state_enabled="true" />
</selector>
here I use two images I made using photoshop as a background
the first is button_clicked and the second is button
copy it and change use your own resources.
hope I could help :)

How can I make an image loop infinitely in Android?

I'm hoping this question will be easy to answer, I have 2 pictures of identical shape and size, I'd like them to infinitely loop from one to the other as soon as the app starts. It would be similar to an animated gif, they wouldn't move or rotate, just loop repeatedly, and very vast (over 10 loops per second at least). A way to adjust the speed in milliseconds would be a big plus.

Try to use FrameAnimation. There is example in docs.
<?xml version="1.0" encoding="utf-8"?>
<animation-list xmlns:android="http://schemas.android.com/apk/res/android"
android:oneshot="false">
<item android:drawable="#drawable/image1" android:duration="200" />
<item android:drawable="#drawable/image2" android:duration="200" />
</animation-list>

how to animate one item of layer-list

I have a layer list object, it contain two images, one is background,
and the other is a rotation disk image which will be raotated at the
top of the background image. i.e. I use this layer-list as a linearlayout background,
and I only want to animate "disk_bg" item of the layer-list;
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/
android">
<item android:drawable="#drawable/player_bg" />
<item android:top="166dp" >
<bitmap android:id="#+id/disk_bg" android:src="#drawable/cd"
android:gravity="center" />
</item>
I use this layer-list as a layout background, do you know how can I animate the disk_bg layer in my application?
can you help me, many thanks to you~
don't you get my question? or there is no way to do that?

First create 2(or more) layer-list resources ie *layer_frame1.xml* and *layer_frame2.xml* , where you set your frames. In your case let's say changing the android:top of the disk item.
Then create an animation-list resource where you set the timing and order of the frames :
<?xml version="1.0" encoding="utf-8"?>
<animation-list xmlns:android="http://schemas.android.com/apk/res/android" android:oneshot="false">
<item
android:drawable="#drawable/layer_frame1"
android:duration="100"/>
<item
android:drawable="#drawable/layer_frame2"
android:duration="100"/>
</animation-list>
Save it in a file ie *drawable/player_animation.xml* and set it as background on a View
<View
android:id="#+id/animation_test"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/player_animation" />
Finally in your code just say when you want the animation start.
((AnimationDrawable)findViewById(R.id.animation_test).getBackground()).start();
Watch out do not start the animation inside onCreate() method.