Question

I’d like to implement an alpha animation when clicking one of the buttons.

The animation is: Alpha down from 1 to 0.5 and when it reaches the 0.5 back again from 0.5 to 1.
Cycling both animations. How can I do it? Is posible to define it in a xml file in /res/anim folder or is necesary to use the AnimationListener?

Thanks

Answer 1

You can use a simple AlphaAnimation object to do this. Set the repeat mode to setRepeatMode(Animation.REVERSE) for changing alpha from 0.5 back to 1.0 and setRepeatCount(count) for number of times to repeat.

sample animation xml:

<alpha
xmlns:android="http://schemas.android.com/apk/res/android"
android:fromAlpha="1.0"
android:toAlpha="0.5"
android:duration="1000" />

code for loading the xml:

Animation a = AnimationUtils.loadAnimation(this, R.anim.alpha);
a.reset();
a.setRepeatMode(Animation.REVERSE);
a.setRepeatCount(5); // will be infinite if -1
Button btn = (Button ) findViewById(R.id.btn);
btn.clearAnimation();
btn.startAnimation(a);

Code is just a sample. Hope this works.