如何将一个 Composable 作为其参数传递给另一个 Composable 并在 Jetpack Compose 中显示/运行它

Question

我在 youtube 上学会了这个抽屉

https://www.youtube.com/watch?v=JLICaBEiJS0&list=PLQkwcJG4YTCSpJ2NLhDTHhi6XBNfk9WiC&index=31 菲利普拉克纳

我想将抽屉添加到我的应用程序中，它有多个屏幕，其中一些不需要抽屉，所以我使用 screens 实现了导航，并且一些屏幕还需要将抽屉放在它们上面。

这是抽屉的代码

val scaffoldState = rememberScaffoldState()
                val scope = rememberCoroutineScope()
                Scaffold(
                    drawerGesturesEnabled = scaffoldState.drawerState.isOpen,
                    scaffoldState = scaffoldState, topBar = {
                    AppBar(onNavigationIconClick = {
                        scope.launch {
                            scaffoldState.drawerState.open()
                        }

                    })
                }, drawerContent = {
                    DrawerHeader()
                    DrawerBody(items = listOf(
                        MenuItem(
                            id = "home",
                            title = "Home",
                            contentDescription = "Go to home screen",
                            icon = Icons.Default.Home
                        ),
                        MenuItem(
                            id = "settings",
                            title = "Settings",
                            contentDescription = "Go to Settings screen",
                            icon = Icons.Default.Settings
                        ),
                        MenuItem(
                            id = "help",
                            title = "Help",
                            contentDescription = "Go to help screen",
                            icon = Icons.Default.Info
                        ),
                    ), onItemClick = {
                        println("Clicked on ${it.title}")

                        when (it.id) {
                            "home" -> {
                                println("Clicked on ${it.title}")
                            }
                            "settings" -> {
                                println("Clicked on ${it.title}")
                            }
                            "help" -> {
                                println("Clicked on ${it.title}")
                            }
                        }
                    })

                }) {

                    Text(text = "Hello World")

                }

Text = Hello world 是我想传递屏幕参数的地方，我不知道该怎么做。我想添加一个参数，该参数采用可组合函数并在内部运行

我关注了这个关于如何在科特林中导航的导航视频

https://www.youtube.com/watch?v=4gUeyNkGE3g&list=PLQkwcJG4YTCSpJ2NLhDTHhi6XBNfk9WiC&index=18

它有 3 个大文件，所以如果你问我在这里发布它们，但我会尝试更具体地说明需要什么

composable(route = Screen.RegisterScreen.route) {
            RegisterScreen(navController = navCotroller)
        }

如果我把代码放在抽屉里，效果很好，但我想把代码拆分得更干净，因为我在更多地方使用抽屉

代码像下面的例子一样工作

composable(route = Screen.PreferenceScreen.route) {
            val scaffoldState = rememberScaffoldState()
            val scope = rememberCoroutineScope()
            Scaffold(

                drawerGesturesEnabled = scaffoldState.drawerState.isOpen,
                scaffoldState = scaffoldState,
                topBar = {
                    AppBar(onNavigationIconClick = {
                        scope.launch {
                            scaffoldState.drawerState.open()
                        }

                    })
                },
                drawerContent = {
                    DrawerHeader()
                    DrawerBody(items = listOf(
                        MenuItem(
                            id = "swipe",
                            title = "Swipe",
                            contentDescription = "Go to Swipe screen",
                            icon = Icons.Default.Home
                        ),
                        MenuItem(
                            id = "settings",
                            title = "Settings",
                            contentDescription = "Go to Settings screen",
                            icon = Icons.Default.Settings
                        ),
                        MenuItem(
                            id = "profile",
                            title = "Profile",
                            contentDescription = "Go to profile screen",
                            icon = Icons.Default.Info
                        ),
                    ), onItemClick = {
                        when (it.id) {
                            "swipe" -> {
                                navCotroller.navigate(Screen.SwipeScreen.route)
                            }
                            "settings" -> {
                                navCotroller.navigate(Screen.PreferenceScreen.route)
                            }
                            "profile" -> {
                                navCotroller.navigate(Screen.CelebProfileScreen.route)
                            }
                        }
                    })

                }) {

         ----->        PreferenceScreen(navController = navCotroller)

            }

        }

但它不是干净的代码！我怎样才能使用函数指针来完成这项工作？？

Answer 1

我无法编译你的代码，我不确定这是否能解决你的问题，但基于此

…我想添加一个参数，它接受一个可组合的函数并运行 它在里面

您可以将其用作参考。考虑这个可组合项，它接受任何可组合项并在内部运行

@Composable
fun AnyComposable(
    anyComposable: @Composable () -> Unit
) {
    anyComposable()
}

另一个使用上面的可组合项并像这样将任何其他可组合项传递给它的可组合项

@Composable
fun MyScreen() {

    // big red Box composable
    val composable1 = @Composable {
        Box (
            modifier = Modifier
                .size(200.dp)
                .background(Color.Red)
        )
    }

    // small blue Box composable
    val composable2 = @Composable {
        Box(
            modifier = Modifier
                .size(80.dp)
                .background(Color.Blue)
        )
    }

    // small green rectangular Box composable
    val composable3 = @Composable {
        Box(
            modifier = Modifier
                .size(width = 100.dp, height = 30.dp)
                .background(Color.Green)
        )
    }

    var dynamicComposable by remember { mutableStateOf<@Composable () -> Unit> (@Composable { composable1() }) }

    Column(
        modifier = Modifier.fillMaxSize(),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {

        Row(
            modifier = Modifier.fillMaxWidth(),
            verticalAlignment = Alignment.CenterVertically,
            horizontalArrangement = Arrangement.SpaceBetween
        ) {
            Button(onClick = {
                dynamicComposable = composable1
            }) {
                Text("Comp 1")
            }

            Button(onClick = {
                dynamicComposable = composable2
            }) {
                Text("Comp 2")
            }

            Button(onClick = {
                dynamicComposable = composable3
            }) {
                Text("Comp 3")
            }
        }

        AnyComposable {
            dynamicComposable()
        }
    }
}

和输出：

Answer 2

或者，如果接收可组合项有一个 Column，并且您想事先使用 Alignment 设置参数可组合项，您可以考虑这个。

接受任何可组合项的同一可组合接收器，但预期布局为 Column。

@Composable
fun AnyComposable(
    anyComposable: @Composable () -> Unit
) {
    Column(
        modifier = Modifier.fillMaxSize()
    ) {
        anyComposable()
    }
}

@Composable
fun MyScreen() {

    // big red box at Start of Column
    val composable1 : @Composable ColumnScope.() -> Unit = @Composable {
        Box (
            modifier = Modifier
                .align(Alignment.Start)
                .size(200.dp)
                .background(Color.Red)
        )
    }

    // small blue box at Center of Column
    val composable2 : @Composable ColumnScope.() -> Unit = @Composable {
        Box(
            modifier = Modifier
                .align(Alignment.CenterHorizontally)
                .size(80.dp)
                .background(Color.Blue)
        )
    }

    // small green rectangle at end of column
    val composable3 : @Composable ColumnScope.() -> Unit = @Composable {
        Box(
            modifier = Modifier
                .align(Alignment.End)
                .size(width = 100.dp, height = 30.dp)
                .background(Color.Green)
        )
    }

    var dynamicComposable by remember { mutableStateOf<@Composable ColumnScope.() -> Unit> (@Composable { composable1() }) }

    Column(
        modifier = Modifier.fillMaxSize(),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {

        Row(
            modifier = Modifier.fillMaxWidth(),
            verticalAlignment = Alignment.CenterVertically,
            horizontalArrangement = Arrangement.SpaceBetween
        ) {
            Button(onClick = {
                dynamicComposable = composable1
            }) {
                Text("Comp 1")
            }

            Button(onClick = {
                dynamicComposable = composable2
            }) {
                Text("Comp 2")
            }

            Button(onClick = {
                dynamicComposable = composable3
            }) {
                Text("Comp 3")
            }
        }

        AnyComposable {
            dynamicComposable()
        }
    }
}

输出：

Answer 3

嘿伙计们，如果你想知道我是如何解决我自己的应用程序中的问题的，请看这段代码

最终结果

https://github.com/dolev146/Politi-Cal/tree/main/app/src/main/java/com/example/politi_cal

这是导航文件 我只是使用答案中描述的概念将屏幕作为参数传递

抽屉包裹内容屏幕的东西

 composable(route = Screen.AdminOnlyScreen.route) {
            DrawerTopBar(navController = navCotroller, screen = { navController ->
                // this is the screen that will be drawn after the drawer
                // swipe screen
                AdminOnlyScreen(navController = navController, auth = auth)

            })
        }

        composable(route = Screen.UserAnalyticsScreen.route) {
            DrawerTopBar(navController = navCotroller, screen = { navController ->
                // this is the screen that will be drawn after the drawer
                // swipe screen


                UserAnalyticsScreen(
                    navController = navController,
                    auth = auth

                )

            })
        }

抽屉看起来像 https://github.com/dolev146/Politi-Cal/tree/main/app/src/main/java/com/example/politi_cal/screens/NavDrawer

// the drawer TopBar should get the navController as a parameter ,
// and the composable screen function that it needs to draw after the drawer
@Composable
fun DrawerTopBar(
    navController: NavController,
    auth: FirebaseAuth = FirebaseAuth.getInstance(),
    screen: @Composable (navController: NavController) -> Unit
) {
    var isAdminState by remember {
        mutableStateOf(false)
    }


    val scaffoldState = rememberScaffoldState()
    val scope = rememberCoroutineScope()
    val context = LocalContext.current
    isAdmin(context) {
        isAdminState = true
    }
    var menuContent = mutableListOf(
        MenuItem(
            id = "search",
            title = "Search",
            contentDescription = "Go to Search screen",
            icon = Icons.Default.Search
        ),

//        MenuItem(
//            id = "swipe",
//            title = "Swipe",
//            contentDescription = "Go to Swipe screen",
//            icon = Icons.Default.Home
//        ),
//        MenuItem(
//            id = "preferences",
//            title = "Preferences",
//            contentDescription = "Go to Preferences screen",
//            icon = Icons.Default.Settings
//        ),
//        MenuItem(
//            id = "logout",
//            title = "Logout",
//            contentDescription = "Go to Logout screen",
//            icon = Icons.Default.ExitToApp
//        ),
//        MenuItem(
//            id = "user analytics",
//            title = "User Analytics",
//            contentDescription = "Go to User Analytics screen",
//            icon = Icons.Default.MoreVert
//        )


    )

    if (isAdminState) {

        menuContent.add(
            MenuItem(
                id = "user analytics",
                title = "Analytics",
                contentDescription = "Go to User Analytics screen",
                icon = Icons.Default.MoreVert
            )
        )



        menuContent.add(
            MenuItem(
                id = "add celeb",
                title = "Add Celeb",
                contentDescription = "Go to User profile screen",
                icon = Icons.Default.Add
            )
        )
        menuContent.add(
            MenuItem(
                id = "admin analytics",
                title = "Admin Analytics",
                contentDescription = "Go to Admin Analytics screen",
                icon = Icons.Default.MoreVert
            )
        )
        menuContent.add(
            MenuItem(
                id = "admin user management",
                title = "User Search",
                contentDescription = "Go to Admin User Management screen",
                icon = Icons.Default.MoreVert
            )
        )











        menuContent.add(
            MenuItem(
                id = "logout",
                title = "Logout",
                contentDescription = "Go to Logout screen",
                icon = Icons.Default.ExitToApp
            )
        )


    } else {
        // this is user menu
        menuContent.add(
            MenuItem(
                id = "swipe",
                title = "Swipe",
                contentDescription = "Go to Swipe screen",
                icon = Icons.Default.Home
            )
        )

        menuContent.add(
            MenuItem(
                id = "user analytics",
                title = "Analytics",
                contentDescription = "Go to User Analytics screen",
                icon = Icons.Default.MoreVert
            )
        )

        menuContent.add(
            MenuItem(
                id = "preferences",
                title = "Preferences",
                contentDescription = "Go to Preferences screen",
                icon = Icons.Default.Settings
            )
        )

        menuContent.add(
            MenuItem(
                id = "my profile",
                title = "My Profile",
                contentDescription = "Go to User profile screen",
                icon = Icons.Default.Person
            )
        )














        menuContent.add(
            MenuItem(
                id = "logout",
                title = "Logout",
                contentDescription = "Go to Logout screen",
                icon = Icons.Default.ExitToApp
            )
        )


    }



    Scaffold(

        drawerGesturesEnabled = scaffoldState.drawerState.isOpen,
        scaffoldState = scaffoldState,
        topBar = {
            AppBar(onNavigationIconClick = {
                scope.launch {
                    scaffoldState.drawerState.open()
                }

            })
        },
        drawerContent = {
            DrawerHeader()
            DrawerBody(items = menuContent, onItemClick = {
                when (it.id) {
                    "swipe" -> {
                        navController.navigate(Screen.SwipeScreen.route)
                    }
                    "preferences" -> {
                        navController.navigate(Screen.PreferenceScreen2.route)
                    }
                    "user profile" -> {
                        navController.navigate(Screen.UserProfileScreen.route)
                    }
                    "add celeb" -> {
                        navController.navigate(Screen.AddCelebScreen.route)
                    }
                    "user analytics" -> {
                        navController.navigate(Screen.UserAnalyticsScreen.route)
                    }
                    "logout" -> {
//                        auth.signOut()
                        navController.navigate(Screen.SplashScreen.route)
                    }
                    "search" -> {
                        navController.navigate(Screen.SearchScreen.route)
                    }
                    "my profile" ->{

                        navController.navigate(Screen.UserProfileScreen.route)
                    }


                    "admin only" -> {
                        // check that the user is admin
                        // if not, show a message
                        // if yes, navigate to the admin only screen
                        if (isAdminState) {
                            navController.navigate(Screen.AdminOnlyScreen.route)
                        } else {
                            // show a message
                            Toast.makeText(context, "You are not an admin", Toast.LENGTH_SHORT)
                                .show()
                        }
                    }
                    "admin analytics" -> {
                        navController.navigate(Screen.AdminAnalyticsMenuScreen.route)
                    }
                    "admin user management" -> {
                        navController.navigate(Screen.AdminUserManagementScreen.route)
                    }


                }
            })

        }) {

        screen(navController = navController)

    }
}

观看链接中的完整代码，如果您喜欢我的解决方案，请点赞 :) 祝您编码愉快