Jetpack Compose AppBar

Version	v1.0.1-alpha2

This package allows easy and light implementation of appbar in jetpack compose environment.

Designed to implement flexible appbar behavior by utilizing only fundamental underlying behaviors and excluding unnecessary features.

How to make appbar?

Please refer to the code below!

See also, this code is the simplest example in this package.

AppBarConnection(
  AppBar(behavior = MaterialAppBarBehavior()) {
    // ... child
  }
  SizedAppBar(minExtent = 50, maxExtent = 100) {
    // ... child
  }
) {
  // Only scrollable component of vertical direction are available.
  // And, can wrapping to parent.
  LazyColumn {
    // ... items
  }
}

How to apply effects according to appbar position?

Please refer to the code below!

See also, this code is an example of implementing transparency effect.

A good example

This example is one of the ideal and simple or basic examples.

// Based on oneself.
AppBarConnection {
  AppBar {
    Box(modifier = Modifier.graphicsLayer {
      alpha = it.expandedPercent()
    }) {
      // ... child
    }
  }
}

// Based on others.
// See also, the second appbar depends on the state of the first appbar.
AppBarConnection {
  val first = rememberAppBarState()

  AppBar(state = first) {
    // ... skip
  }
  AppBar {
    Box(modifier = Modifier.graphicsLayer {
      alpha = first.shrinkedPercent()
    }) {
      // ... child
    }
  }
}

A bad example

This example is also one of the bad development habits that causes performance degradation.

AppBarConnection {
  AppBar {
    // This reduces performance, because re-composition when scrolled appbar.
    Box(modifier = Modifier.alpha(it.expandedPercent())) {
      // ... child
    }
  }
}

How to customize appbar alignment?

Try applying the AppBarAlignment that is a providing standard enumeration in this package.

This alignment constants for only the hide-able appbar.

AppBarConnection(
  AppBar(alignment = AppBarAlignment.Center) {}
)

properties of AppBarAlignment

Properie	Description
Scroll	Display the same as the scroll item. (is Default Value)
Center	Based on the size of the appbar, the center is located at the center of the size of the appbar.
Absolute	Even if the appbar is reduced and expanded, the absolute position of the appbar does not change.

How to customize appbar?

Try using the MaterialAppBarBehavior that is a providing standard feature in this package.

AppBarConnection {
  AppBar(behavior = MaterialAppBarBehavior(floating = false, dragOnlyExpanding = true)) {}
}

properties of MaterialAppBarBehavior

When the value of floating is true, the value of dragOnlyExpanding must be false.

Properie	Description	Default value	Type
floating	Whether possible with the app bar expands or shrinks even if a user do not scroll to the highest upper (when scroll offset 0).	true	boolean
dragOnlyExpanding	Whether only possible with drag when the user needs to start extending the appbar.	false	boolean