Our Journey Through Jetpack Compose

Before diving in, let’s take a moment to reflect on what we’ve covered so far in our series. Here’s a brief overview of the chapters leading up to this one:

• Chapter 01: Diving Into Declarative UIs: The Jetpack Compose Revolution
• Chapter 02: Your First Spell: Conjuring Up a Composable Function
• Chapter 03: Stacking Blocks: Crafting Simple Layouts with Magic
• Chapter 04: The Power of Modifiers: Tailoring Your UI's Style and Behavior
• Chapter 05: The Mighty Button: Triggering Actions with a Tap
• Chapter 06: Text Quest: Adding Words to Your World
• Chapter 07: Creating Space: The Art of Using Spacers
• Chapter 08: The Flexibility of Columns & Rows: Building Fluid Layouts
• Chapter 09: TextField Challenge: Summoning Input Fields from the Ether
• Chapter 10: TextField Alchemy: Customizing Your Input Fields
• Chapter 11: A Picture's Worth: Displaying Images with Jetpack Compose
• Chapter 12: Tick and Pick: Mastering Checkboxes & Radio Buttons
• Chapter 13: The Scaffold Tower: Constructing Complex Layouts with Ease
• Chapter 14: The Lazy River: Displaying Lists with Lazy Layouts
• Chapter 15: The State of Code Magic: Managing UI State in Jetpack Compose (YOU ARE HERE)
• Chapter 16: The Magic Behind the Curtain: Understanding Recomposition

Let's embark on our journey into State Management!

Section 1.1: Understanding State

What exactly is "state" in the context of UI development? In simple terms, state refers to data that changes over time, making it a mutable entity. For instance, the content that a user types into a TextField is a prime example of mutable state. This concept is crucial for transforming static interfaces into dynamic ones.

Consider the SearchBar (ArcaneSearchOrb) Composable we touched upon earlier. It's merely a static form until we assign a state to it. Two important terms related to understanding state in Jetpack Compose are:

• Composition: This is the process of defining the UI by invoking the same Composable with varying parameters.
• Recomposition: This is the act of updating the UI when the underlying state changes.

Section 1.2: Applying State Management Techniques

To effectively manage state in Jetpack Compose, we can utilize the "remember" API. This API allows us to capture state that is scoped to a Composable. Notably, values computed using "remember" are retained during the initial composition and retrieved during recomposition.

There are three primary methods to declare a MutableState using the "remember" API:

1. val myState = remember { mutableStateOf(defaultValue) }
2. val myState by remember { mutableStateOf(defaultValue) }
3. val (myState, changeMyState) = remember { mutableStateOf(10) }

All three methods serve the same purpose, but the third one provides a function to update the state, typically triggered by an event.

Let’s see how to implement this in a SearchBar Composable:

@ExperimentalMaterial3Api

@Composable

fun OurSearchBar() {

var searchString by remember { mutableStateOf("") }

Card(

modifier = Modifier

.fillMaxWidth()

.height(80.dp)

.padding(end = 20.dp, start = 20.dp, top = 10.dp),

shape = RoundedCornerShape(100.dp),

) {

TextField(

modifier = Modifier.fillMaxSize(),

value = searchString,

onValueChange = { searchString = it },

leadingIcon = { Image(painter = painterResource(id = R.drawable.ic_loup), contentDescription = "Search Icon") },

trailingIcon = { Image(painter = painterResource(id = R.drawable.ic_filter_list), contentDescription = "Filter Icon") },

placeholder = {

Text(

text = "Search here...",

modifier = Modifier

.fillMaxHeight(),

textAlign = TextAlign.Center,

)

},

colors = TextFieldDefaults.textFieldColors(

focusedIndicatorColor = Color.Transparent,

unfocusedIndicatorColor = Color.Transparent,

),

)

}

}

Section 1.3: Practical Example of State Management

Let’s continue building our user interface with various components. Here’s how to arrange them effectively:

@Composable

fun OurHome() {

Surface(modifier = Modifier) {

Column(

modifier = Modifier

.fillMaxSize()

.padding(top = 16.dp)

.padding(horizontal = 8.dp),

) {

// Custom Categories header

Row(

modifier = Modifier

.fillMaxWidth(),

horizontalArrangement = Arrangement.SpaceBetween,

) {

Text(text = "Some Groups")

Row(modifier = Modifier, verticalAlignment = Alignment.CenterVertically) {

Text(

text = "Discover",

color = MaterialTheme.colorScheme.primary,

fontWeight = FontWeight.Bold,

)

Spacer(modifier = Modifier.width(10.dp))

Image(

painter = painterResource(id = R.drawable.ic_right),

content_description = "See more",

colorFilter = ColorFilter.tint(color = MaterialTheme.colorScheme.primary),

)

}

}

// Additional UI components can be added here

}

}

}