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

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

贡献者: Junyuan He