Level 22

Runtime Permissions

ActivityResult API & rememberLauncherForActivityResult

Dangerous permissions (camera, location, notifications) must be requested at runtime and can be revoked anytime. The modern way is the `ActivityResult` contract, which you launch from a Composable.

📚 Explanation

Runtime permissions use the `ActivityResult` API instead of the old `onRequestPermissionsResult` callback. `rememberLauncherForActivityResult` registers a launcher with the `RequestPermission()` contract and survives recomposition; calling `launcher.launch(...)` shows the system dialog and delivers the boolean result to your lambda. Always re-check with `checkSelfPermission` because the user can revoke a grant from Settings while your app is in the background — never assume a one-time grant is permanent.

Note: Code execution is not available for Android/Kotlin in the browser. Use Android Studio to run and test the app.

kotlin

import android.Manifest
import android.content.pm.PackageManager
import androidx.activity.compose.rememberLauncherForActivityResult
import androidx.activity.result.contract.ActivityResultContracts
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.platform.LocalContext
import androidx.core.content.ContextCompat

@Composable
fun CameraPermissionGate(onGranted: () -> Unit) {
    val context = LocalContext.current

    // Re-check current grant state each composition
    var hasPermission by remember {
        mutableStateOf(
            ContextCompat.checkSelfPermission(
                context, Manifest.permission.CAMERA
            ) == PackageManager.PERMISSION_GRANTED
        )
    }

    // 1. Register a launcher tied to the permission contract
    val launcher = rememberLauncherForActivityResult(
        contract = ActivityResultContracts.RequestPermission()
    ) { granted ->
        hasPermission = granted
        if (granted) onGranted()
    }

    if (hasPermission) {
        Text("Camera ready")
    } else {
        Button(onClick = {
            // 2. Launching shows the system dialog
            launcher.launch(Manifest.permission.CAMERA)
        }) {
            Text("Grant camera access")
        }
    }
}

Back to Android Levels Back to Developer Hub

Runtime Permissions

ActivityResult API & rememberLauncherForActivityResult

Dangerous permissions (camera, location, notifications) must be requested at runtime and can be revoked anytime. The modern way is the `ActivityResult` contract, which you launch from a Composable.

📚 Explanation

Note: Code execution is not available for Android/Kotlin in the browser. Use Android Studio to run and test the app.

import android.Manifest

import android.content.pm.PackageManager

import androidx.activity.compose.rememberLauncherForActivityResult

import androidx.activity.result.contract.ActivityResultContracts

import androidx.compose.material3.*

import androidx.compose.runtime.*

import androidx.compose.ui.platform.LocalContext

import androidx.core.content.ContextCompat

@Composable

fun CameraPermissionGate(onGranted: () -> Unit) {

val context = LocalContext.current

// Re-check current grant state each composition

var hasPermission by remember {

mutableStateOf(

ContextCompat.checkSelfPermission(

context, Manifest.permission.CAMERA

) == PackageManager.PERMISSION_GRANTED

)

}

// 1. Register a launcher tied to the permission contract

val launcher = rememberLauncherForActivityResult(

contract = ActivityResultContracts.RequestPermission()

) { granted ->

hasPermission = granted

if (granted) onGranted()

}

if (hasPermission) {

Text("Camera ready")

} else {

Button(onClick = {

// 2. Launching shows the system dialog

launcher.launch(Manifest.permission.CAMERA)

}) {

Text("Grant camera access")

}