making the gif start from the begining after closing and reopening it - flutter

Question

I am trying to make this gif appears when clicking on the floating action button and popint it again after pressing on ok:
https://66.media.tumblr.com/1ce23970665b7736bd857720ebf5a5b2/tumblr_pp3sftPVIy1wb1n5x_540.gif
The problem is that when I click ok and reclick the floating action button, the gif continue from it stopped last time I pressed ok; I want it to start from the begining every time I click the floating action button. How can I do this? Here's the code:
floatingActionButton: FloatingActionButton(
child: Icon(Icons.healing),
onPressed: () {
showDialog(
context: context,
builder: (_) => Container(
height: 200.0,
child: NetworkGiffyDialog(
// key: keys[1],
image: Image.network(
gif,
fit: BoxFit.fitHeight,
),
title: Text("Exercises of breathing"),
description: Text(
'This will help you with breathing exercises to overcome anxiety attacks',
),
entryAnimation: EntryAnimation.RIGHT,
onOkButtonPressed: () {
Navigator.of(context).pop();
},
),
),
);
},
//child: new Text("Breathing exercise"),
),
EDIT: I followed the first answer and tried to switch between null value and the gif link as follows, however i still have the same problem
floatingActionButton: FloatingActionButton(
child: Icon(Icons.healing),
onPressed: () {
setState(() => gif = giflink);
showDialog(
context: context,
builder: (_) => Container(
height: 200.0,
child: NetworkGiffyDialog(
// key: keys[1],
image: Image.network(
gif,
fit: BoxFit.fitHeight,
),
title: Text("Exercises of breathing"),
description: Text(
'This will help you with breathing exercises to overcome anxiety attacks',
),
entryAnimation: EntryAnimation.RIGHT,
onOkButtonPressed: () {
Navigator.of(context).pop();
setState(() => gif = null);
},
),
),
);
},
//child: new Text("Breathing exercise"),
),

Answer 1

One thing you can try is using your variable gif as setState a null value to it after the animation (GIF duration) ends (or if user cancels).
var gif = "https://theurlofyourgif.com/file.gif"
void doYourGIFLogic() {
// show it with a Navigator, or Opacity, or Visibility, etc
// wait for that animation (GIF duration) to be done
final NetworkImage provider = NetworkImage(gif);
provider.evict().then<void>((bool success) {
if (success) {
print('removed image!');
}
});
}
When the user clicks again using the FAB, the cache will be cleared and the GIF should start from the beginning.