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Shifting Paradigms Ragunath Jawahar / @ragunathjawahar

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One moment…

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Data Binding

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Progress Bar?

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Hiccups • A decade old UI toolkit • Bug fixes in the framework require OS updates • Multiple tech stacks • Multiple sources of truth • Accidental complexity

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Jetpack Compose

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⛔

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⛔

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⛔

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⛔

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⛔

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⚠

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• Component-based UI framework • Declarative • Favours composition over inheritance • Unbundled UI Toolkit • Kotlin only • “Pre-Alpha” ⚠

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Components 1. Compose Runtime 2. Compose Compiler Plugin 3. Compose UI

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Components 1. Compose Runtime 2. Compose Compiler Plugin 3. Compose UI

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Components 1. Compose Runtime 2. Compose Compiler Plugin 3. Compose UI

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Components 1. Compose Runtime 2. Compose Compiler Plugin 3. Compose UI

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Components 1. Compose Runtime 2. Compose Compiler Plugin 3. Compose UI

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Mental Model

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ui = f(s)

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ui = f(s)

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ui = f(s)

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ui = f(s)

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ui = f(s)

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No more references to views

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@Composable fun Text( text: String, style: TextStyle? = null, textAlign: TextAlign = DefaultTextAlign, // More parameters… ) { // More code… } Composable functions

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@Composable fun Text( text: String, style: TextStyle? = null, textAlign: TextAlign = DefaultTextAlign, // More parameters… ) { // More code… } Composable functions

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@Composable fun Text( text: String, style: TextStyle? = null, textAlign: TextAlign = DefaultTextAlign, // More parameters… ) { // More code… } Composable functions

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@Composable fun Text( text: String, style: TextStyle? = null, textAlign: TextAlign = DefaultTextAlign, // More parameters… ) { // More code… } Composable functions

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A Composed Example (pun intended)

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⚠

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ui = f(s)

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ui = f(s)

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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@Model data class Fruit( val name: String, val price: Double = 2.0, var quantity: Int = 0 ) { val totalPrice: Double get() = quantity * price }

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ui = f(s)

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ui = f(s) ✅

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ui = f(s)

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ui = f(s)

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Stepper

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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@Composable fun Stepper(count: Int, onCountChange: (Int) P> Unit) { val onRemoveOne = { onCountChange(count - 1) } val onAddOne = { onCountChange(count + 1) } Row { Button(text = "-", onClick = if (count > 0) onRemoveOne else null) WidthSpacer(8.dp) Container(width = 24.dp) { Text(text = "$count", style = +themeTextStyle { body1 }) } WidthSpacer(8.dp) Button(text = "+", onClick = onAddOne) } }

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Stepper

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Stepper ✅

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Fruit Row

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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@Composable fun FruitRow(fruit: Fruit) { Padding(padding = EdgeInsets(left = 16.dp, right = 16.dp)) { FlexRow { expanded(1.0f) { Text(text = "${fruit.name} ($${fruit.totalPrice})", style = +themeTextStyle { h6 }) } inflexible { Stepper(fruit.quantity, onCountChange = { fruit.quantity = it }) } } } }

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Fruit Row

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Fruit Row ✅

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State?

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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FruitApp { val apple = +memo { Fruit("Apple", price = 2.0) } FruitRow(apple) }

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Observations • Smallest reusable unit is a function • Stateless widgets (“controlled components”) • Single source of truth • Structure of the code matches the structure of the view hierarchy • UI was built from leaf to node • State stays as close to the root as possible • Declarative • Reduction in boilerplate

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Resources • http://intelligiblebabble.com/content-on-declarative-ui/ • http://intelligiblebabble.com/compose-from-first-principles/ • https://www.youtube.com/watch?v=4EFjDSijAZU • https://github.com/SimonSchubert/Braincup • https://developer.android.com/jetpack/compose • #compose channel at https://kotlinlang.slack.com/ • https://speakerdeck.com/benoberkfell/prototyping-with- jetpack-compose?slide=67

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@ragunathjawahar Twitter / Medium / GitHub end;