最近的畫面

private fun newDocumentIntent(context: Context): Intent =
    Intent(context, NewDocumentActivity::class.java).apply {
        addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT or Intent.FLAG_ACTIVITY_RETAIN_IN_RECENTS)
        putExtra(KEY_EXTRA_NEW_DOCUMENT_COUNTER, documentCounter++)
    }

@Composable
fun CreateDocumentButton() {
    val context = LocalContext.current
    Button(
        onClick = {
            val intent = newDocumentIntent(context)
            // Add FLAG_ACTIVITY_MULTIPLE_TASK if needed based on state
            context.startActivity(intent)
        }
    ) {
        Text("Create New Document")
    }
}

class DocumentCentricActivity : ComponentActivity() {
    private var documentState by mutableStateOf(
        DocumentState(
            count = 0,
            textResId = R.string.hello_new_document_counter
        )
    )

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

        val initialCount = intent.getIntExtra(KEY_EXTRA_NEW_DOCUMENT_COUNTER, 0)

        documentState = documentState.copy(count = initialCount)

        setContent {
            MaterialTheme {
                DocumentScreen(
                    count = documentState.count,
                    textResId = documentState.textResId
                )
            }
        }
    }

    override fun onNewIntent(newIntent: Intent) {
        super.onNewIntent(newIntent)
        // If FLAG_ACTIVITY_MULTIPLE_TASK has not been used, this Activity is reused.
        documentState = documentState.copy(
            textResId = R.string.reusing_document_counter
        )
    }

    data class DocumentState(val count: Int, @StringRes val textResId: Int)

    companion object {
        const val KEY_EXTRA_NEW_DOCUMENT_COUNTER = "KEY_EXTRA_NEW_DOCUMENT_COUNTER"
    }
}

@Composable
fun DocumentScreen(count: Int, @StringRes textResId: Int) {
    Column(
        modifier = Modifier
            .fillMaxSize()
            .padding(16.dp),
        verticalArrangement = Arrangement.Center
    ) {
        // UI reacts to whichever string resource ID was passed down
        Text(text = stringResource(id = textResId))
        Spacer(modifier = Modifier.height(8.dp))
        Text(text = "Counter: $count")
    }
}

@Composable
fun RemoveTaskButton() {
    val context = LocalContext.current
    Button(
        onClick = {
            // It is good practice to remove a document from the overview stack if not needed anymore.
            (context as? Activity)?.finishAndRemoveTask()
        }
    ) {
        Text("Remove from Recents")
    }
}

private fun newDocumentIntent() =
        Intent(this, NewDocumentActivity::class.java).apply {
            addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT or
                    android.content.Intent.FLAG_ACTIVITY_RETAIN_IN_RECENTS)
            putExtra(KEY_EXTRA_NEW_DOCUMENT_COUNTER, getAndIncrement())
        }

class MainActivity : ComponentActivity() {

    // Track the current URL as state so the UI can update it during navigation
    private var currentWebUri by mutableStateOf("https://example.com/home")

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

        setContent {
            AppTheme {
                // Pass a lambda to your Compose UI so it can update the URL state
                // as the user navigates through your app.
                MainScreen(
                    onPageChanged = { newUrl -> currentWebUri = newUrl }
                )
            }
        }
    }

    override fun onProvideAssistContent(outContent: AssistContent) {
        super.onProvideAssistContent(outContent)

        // The system calls this when the user enters the Recents screen.
        // Provide the active URI tracked by the Compose state.
        outContent.webUri = Uri.parse(currentWebUri)
    }
}