What is Tween in the context of Flutter application development?

Tween is a class in Flutter that defines a range of values between a start and an end value. It does not perform actual animation by itself but works together with an Animation object to interpolate values over a certain period.

Main features:

• Value Range: Tween<T> takes a starting value begin and an ending value end of type T.
• Interpolation: The evaluate() method returns an interpolated value based on the current Animation value. The Animation value is usually in the range [0.0, 1.0]. At 0.0, evaluate() returns begin, at 1.0 — end, and between them — a linearly interpolated value.
• Typing: Tween is generic and can work with various data types such as double, int, Color, Rect, and others, if a corresponding lerp (linear interpolation) method is defined for them.
• Combination with Animation: Tween is combined with an Animation object (usually created by an AnimationController). The Animation provides the current "position" in the animation (from 0.0 to 1.0), and the Tween uses this position to compute the interpolated value.

Example usage:

// Create a Tween for interpolating numbers from 0 to 100
final tween = Tween<double>(begin: 0.0, end: 100.0);

// Get the value from the Tween based on the Animation value (e.g., from an AnimationController)
// Assume animation.value = 0.5
final animatedValue = tween.evaluate(animation); // animatedValue will be 50.0

Thus, Tween is a fundamental building block for creating animations in Flutter, allowing you to define how property values should change over time.