Android Permissions and Compose State-Driven UI

About 319 wordsAbout 1 min

2025-12-23

1. Background

This was my first time working with native Android app development. The app I wanted to build needed camera access, and Android 6.0 (API 23) and above requires runtime permission requests for sensitive permissions such as camera, microphone, or storage.

In our project, we needed the CAMERA permission to display the rear CameraX preview inside a Compose app.

2. Declaring permissions in the Manifest

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera.any" android:required="true"/>

uses-permission: tells the system that the app needs the CAMERA permission
uses-feature: declares a dependency on camera hardware
Declaring a permission is not the same as having it granted

3. Runtime permission requests

Modern Android recommends the Activity Result API together with Compose state.

1. Register the permission launcher

private lateinit var cameraPermissionLauncher: ActivityResultLauncher<String>

cameraPermissionLauncher = registerForActivityResult(
    ActivityResultContracts.RequestPermission()
) { granted ->
    hasCameraPermission.value = granted
}

registerForActivityResult registers the request and callback
ActivityResultContracts.RequestPermission is the built-in contract for a single permission
granted: Boolean tells you whether the user allowed it
Updating state triggers Compose recomposition automatically

2. Launch the permission request

cameraPermissionLauncher.launch(Manifest.permission.CAMERA)

4. Compose state-driven UI

val hasCameraPermission = mutableStateOf(
    ContextCompat.checkSelfPermission(
        this,
        Manifest.permission.CAMERA
    ) == PackageManager.PERMISSION_GRANTED
)

true -> show CameraPreview
false -> show the permission request button

Surface(
    modifier = Modifier.fillMaxSize(),
    color = MaterialTheme.colorScheme.background
) {
    if (hasCameraPermission.value) {
        CameraPreview(activity = this)
    } else {
        NoPermissionView(
            onRequestPermission = {
                cameraPermissionLauncher.launch(Manifest.permission.CAMERA)
            }
        )
    }
}

Compose state-driven UI responds to permission changes automatically.

5. `NoPermissionView` example

@Composable
fun NoPermissionView(onRequestPermission: () -> Unit) {
    Box(
        modifier = Modifier.fillMaxSize(),
        contentAlignment = Alignment.Center
    ) {
        Button(
            onClick = onRequestPermission,
            modifier = Modifier.width(200.dp).height(60.dp)
        ) {
            Text("请求相机权限")
        }
    }
}

6. What I learned

Manifest declaration and runtime authorization are different things
ActivityResultLauncher + Compose state is a clean pattern
State-driven UI removes the need for manual refresh logic
Callbacks help keep asynchronous logic separate from rendering