Day 27 Compose UI Drawer

今年的疫情蠻嚴重的，希望大家都過得安好，希望疫情快點結束，能回到一些線下技術聚會的時光～
今天目標：了解 Compose UI 上 Drawer 怎麼使用。

Drawer的需求也是蠻常見的，今天的完成圖如下：

profile 圖是沿用 Day 7的～

我覺得這部分的程式碼跟昨天比起來，相對容易了解～
程式如下：

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            AppMainScreen()
        }
    }
sealed class DrawerScreens(val title: String, val route: String) {
        object Home : DrawerScreens("Home", "home")
        object Account : DrawerScreens("Account", "account")
        object Help : DrawerScreens( "Help", "help")
    }
private val screens = listOf(
        DrawerScreens.Home,
        DrawerScreens.Account,
        DrawerScreens.Help
    )
@Composable
    open fun AppMainScreen() {
        val navController = rememberNavController()
        Surface(color = MaterialTheme.colors.background) {
            val drawerState = rememberDrawerState(DrawerValue.Closed)
            val scope = rememberCoroutineScope()
            val openDrawer = {
                scope.launch {
                    drawerState.open()
                }
            }
            ModalDrawer(
                drawerState = drawerState,
                gesturesEnabled = drawerState.isOpen,
                drawerContent = {
                    Drawer(
                        onDestinationClicked = { route ->
                            scope.launch {
                                drawerState.close()
                            }
                            navController.navigate(route) {
                                popUpTo = navController.graph.startDestinationId
                                launchSingleTop = true
                            }
                        }
                    )
                }
            ) {
                NavHost(
                    navController = navController,
                    startDestination = DrawerScreens.Home.route
                ) {
                    composable(DrawerScreens.Home.route) {
                        Home(
                            openDrawer = {
                                openDrawer()
                            }
                        )
                    }
                    composable(DrawerScreens.Account.route) {
                        Account(
                            openDrawer = {
                                openDrawer()
                            }
                        )
                    }
                    composable(DrawerScreens.Help.route) {
                        Help(
                            navController = navController
                        )
                    }
                }
            }
        }
    }
@Composable
    fun Drawer(
        modifier: Modifier = Modifier,
        onDestinationClicked: (route: String) -> Unit
    ) {
        Column(
            modifier
                .fillMaxSize()
                .padding(start = 24.dp, top = 48.dp)
        ) {
            Image(
                painter = painterResource(R.drawable.profile_picture),
                contentDescription = "App icon"
            )
            screens.forEach { screen ->
                Spacer(Modifier.height(24.dp))
                Text(
                    text = screen.title,
                    style = MaterialTheme.typography.h4,
                    modifier = Modifier.clickable {
                        onDestinationClicked(screen.route)
                    }
                )
            }
        }
    }
@Composable
    fun TopBar(title: String = "", buttonIcon: ImageVector, onButtonClicked: () -> Unit) {
        TopAppBar(
            title = {
                Text(
                    text = title
                )
            },
            navigationIcon = {
                IconButton(onClick = { onButtonClicked() } ) {
                    Icon(buttonIcon, contentDescription = "")
                }
            },
            backgroundColor = MaterialTheme.colors.primaryVariant
        )
    }
@Composable
    fun Home(openDrawer: () -> Unit) {
        Column(modifier = Modifier.fillMaxSize()) {
            TopBar(
                title = "Home",
                buttonIcon = Icons.Filled.Menu,
                onButtonClicked = { openDrawer() }
            )
            Column(
                modifier = Modifier.fillMaxSize(),
                verticalArrangement = Arrangement.Center,
                horizontalAlignment = Alignment.CenterHorizontally) {
                Text(text = "Home Page content here.")
            }
        }
    }
@Composable
    fun Account(openDrawer: () -> Unit) {
        Column(modifier = Modifier.fillMaxSize()) {
            TopBar(
                title = "Account",
                buttonIcon = Icons.Filled.Menu,
                onButtonClicked = { openDrawer() }
            )
            Column(
                modifier = Modifier.fillMaxSize(),
                verticalArrangement = Arrangement.Center,
                horizontalAlignment = Alignment.CenterHorizontally) {
                Text(text = "Account.", style = MaterialTheme.typography.h4)
            }
        }
    }
@Composable
    fun Help(navController: NavController) {
        Column(modifier = Modifier.fillMaxSize()) {
            TopBar(
                title = "Help",
                buttonIcon = Icons.Filled.ArrowBack,
                onButtonClicked = { navController.popBackStack() }
            )
            Column(
                modifier = Modifier.fillMaxSize(),
                verticalArrangement = Arrangement.Center,
                horizontalAlignment = Alignment.CenterHorizontally) {
                Text(text = "Help.", style = MaterialTheme.typography.h4)
            }
        }
    }

我覺得 Drawer 這個元件在概念上最簡單的實現方式，
就是把就是把昨天的 Navigation 加上一層左邊的 Comlumn 顯示？

不過我還是查了一下相關資料，原來還有其他的延伸做法～放在參考資料區，有興趣的人在自己研究看看囉～理解的話今天就結束了～
然後，明天見囉！
參考資料：
https://proandroiddev.com/navigation-drawer-using-jetpack-compose-27ea7db74903
https://medium.com/android-news/exploring-drawers-in-jetpack-compose-3131e6f1b07b

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