android - Change alpha of image view by clicking button -

i'm developing android project.

in project have imageview , button. when user clicks on button, want imageview's alpha change 1 0.5 , change 0.5 1.

i wrote following code:

public void animate(imageview imageview) {     int animduration = 50;     int timebetween = 2;      alphaanimation animation1 = new alphaanimation(1, (float) 0.5);     animation1.setinterpolator(new accelerateinterpolator());     animation1.setduration(animduration);      alphaanimation animation2 = new alphaanimation((float) 0.5, 1);     animation2.setinterpolator(new accelerateinterpolator());     animation2.setstartoffset(animduration + timebetween);     animation2.setduration(animduration);      animationset animation = new animationset(true);     animation.addanimation(animation1);     animation.addanimation(animation2);     animation.setrepeatcount(1);      imageview.setanimation(animation); } 

and pass imageview function when user clicks on it.

but doesn't work correctly, , nothing changes. problem?

from view.setanimation() documentation (emphasis mine):

sets next animation play view. if want animation play immediately, use startanimation(android.view.animation.animation) instead. method provides allows fine-grained control on start time , invalidation, must make sure 1) the animation has start time set, , 2) view's parent (which controls animations on children) invalidated when animation supposed start.

although have set start offset animation2, did not set start time animationset itself, , view has no idea when start animation.

if want animation start immediately, use startanimation() instead. if want animations start @ specific time, call setstarttime() or setstartoffset() on animationset.