What is addListener in Dart?

addListener method Null safety Adds a listener callback that is called whenever a new concrete ImageInfo object is available or an error is reported . If a concrete image is already available, or if an error has been already reported, this object will notify the listener synchronously.

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How do you update value in flutter?

To update the value of data points, re-initialize the data source collection and use the setState() method . In the following example, we have called the setState() method in the onPressed() event of a button. For more information, refer to the Updating the Existing Flutter Chart Data Point Value project demo.

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