How to write condition statements in flutter? - android-studio

Question

I wanted to learn how can I apply "if" condition in my flutter code? As I am new to dart language coding.
Suppose in a code like below, i want to add condition that if the counter's value is 1 then "You have pushed the button $_counter time" else "You have pushed the button $_counter times"
children: <Widget>[
new Text(
'You have pushed the button $_counter times:',
)/*,
new Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),*/
]
P.S. its just a simple example for me to understand how to use if condition in flutter.

Answer 1

For such simple cases you can use the ternary if ?: inside string interpolation:
new Text(
'You have pushed the button $_counter time${_counter != 1 ? 's' : ''}:',
)

Answer 2

for the case of the conditions you have just a single condition then you can use the basic ternary operators,
child: Text(
'{fee=="FREE"?"Free":fee}',
),
But if you have multiple conditions or value that need to compare from the index position(i.e. you have to fetch value and then need to put in condition) in listview then you can add method as your text value in your Widget as follows:
child: Text(
'${checkForPrice(index)}',
),
),
checkForPrice(int index) {
String strFee = data['payload']['webinar'][index]['fee'];
String finalFee = "";
if (strFee == "FREE") {
finalFee = 'FREE';
} else {
finalFee = '\$ ${data['payload']['webinar'][index]['fee']}';
}
return finalFee;}
This will definitely help you in showing data with multiple conditions.

Answer 3

at the first time i tried flutter i have no idea what dart language is but after some browsing i found this useful documentation. You can find anything you looking for right there including if statement that you are asking about. But i can tell you the if statement works the same as any other language such as JavaScript, Java, etc.
Edit: here i give you some example how to use it in flutter
Future<Null> toTheHomeScreen() async {
await _signInWithGoogle();
SharedPreferences sprefs = await SharedPreferences.getInstance();
if (sprefs.getString('idToken').isNotEmpty) {
new Future.delayed(new Duration(seconds: 3), () {
new CircularProgressIndicator();
Navigator.of(context).push(
new MaterialPageRoute(
builder: (BuildContext context) {
return new HomeScreen();
}
)
);
});
} else {
Navigator.of(context).pop();
}
}
the if statement check if there is any key named 'idToken' stored in sharedpref, if it not empty user will redirect to home page.
I hope this will help you.