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Use state and events

Required dependencies​

This page is standalone. Add Maven Central and the Android host before copying the example. The host supplies runtime state and widget APIs transitively:

build.gradle.kts
repositories { mavenCentral() }

dependencies {
    implementation("com.viewcompose:viewcompose-material3-android:0.1.0-alpha02")
    implementation("androidx.activity:activity:1.12.4")
    implementation("com.google.android.material:material:1.13.0")
}

Build a counter​

Create StateTutorialActivity.kt. The file owns its state, UI, and Android host, so it does not depend on another tutorial file.

package com.viewcompose.samples.tutorials

import android.os.Bundle
import androidx.activity.ComponentActivity
import com.viewcompose.material3.android.setMaterial3UiContent
import com.viewcompose.runtime.mutableStateOf
import com.viewcompose.ui.modifier.Modifier
import com.viewcompose.ui.modifier.fillMaxSize
import com.viewcompose.ui.modifier.padding
import com.viewcompose.ui.unit.dp
import com.viewcompose.ui.foundation.Button
import com.viewcompose.ui.foundation.Column
import com.viewcompose.ui.foundation.Text
import com.viewcompose.ui.foundation.TextDefaults
import com.viewcompose.ui.foundation.remember

class StateTutorialActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setMaterial3UiContent {
            val count = remember { mutableStateOf(0) }

            Column(
                spacing = 12.dp,
                modifier = Modifier.fillMaxSize().padding(24.dp),
            ) {
                Text("Count: ${count.value}", style = TextDefaults.titleLargeStyle())
                Button("Increment", onClick = { count.value += 1 })
            }
        }
    }
}

Register the Activity in AndroidManifest.xml and run it. remember keeps the state object while the composition is alive. Reading count.value subscribes the UI; changing it in onClick rebuilds the affected description and patches the existing native text View.

Verify the result​

The screen starts at Count: 0. Each press of Increment increases the number. Compile the exact repository example with:

./gradlew :samples:tutorials:assembleDebug

For state that must survive Activity recreation, continue with Lifecycle and SavedState.