AlphaAnimation does not work

Question

I have been looking for a solution to my problem. But my code seems to be ok.

I'll try to explain: I have a TextView with android:alpha="0" in my layout definition. I want (when a image is clicked) show that TextView with an AlphaAnimation, from 0.0f to 1.0f.

My problem is that when I click the image, nothing happens. But the strange thing, is that if I set it's alpha to 1 in the layout definition, and I click the image, I can see the animation (alpha 1 -> alpha 0 -> alpha 1).

What am I doing wrong?

My code:

TextView tv = (TextView) findViewById(R.id.number);

AlphaAnimation animation1 = new AlphaAnimation(0.0f, 1.0f);
animation1.setDuration(1000);
animation1.setFillAfter(true);
tv.startAnimation(animation1);

Thanks in advance.

Solution 1

The problem is in android:alpha="0". This property sets transparency of a View http://developer.android.com/reference/android/view/View.html#attr_android:alpha

When alpha property is equal to 0 then animation is changing transparency from 0*0.0f=0 to 0*1.0f=0. When alpha property is set to 1 then animation is changing transparency from 1*0.0f=0 to 1*1.0f=1. That's why in first case you can't see text and in the second everything works as expected.

To make things work you have to set visibility property to invisible in layout xml. And before starting alpha animation call tv.setVisibility(View.VISIBLE);

Solution 2

More simple way is presented in this answer:

tv.animate().alpha(1).setDuration(1000);

Comments

[jjimenez]

Thanks for the response vasart. I will try it when I will arrive to home. But, I think that doing that, before the animation start I will see the TextView element will appear whith alpha 1, and then it will start its animation. Is that right? What I want to do is that the TextView appears slowly in my view.

[vasart]

It should appear slowly without flickering at start

[AXSM]

I seems a partial response, what happen if i set android:visibility="INVISIBLE or GONE", the animation to alpha 1 doesnt work. looks like property animator need the view.

[Pierre]

Use Invisible instead of Gone was what did the trick. Gone == Alpha 0