# MultipleBackStackCompose

**Repository Path**: ggbhack/multiple-back-stack-compose

## Basic Information

- **Project Name**: MultipleBackStackCompose
- **Description**: compose 学习分享
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2023-12-14
- **Last Updated**: 2023-12-14

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README


## 主页面

```kotlin
 MultipleBackstacksComposeTheme {
                //处理应用程序内的导航
                val rootNavController = rememberNavController()
                // 这行代码从NavController中获取当前的返回栈条目，并创建一个状态，以便在返回栈发生变化时自动更新
                val navBackStackEntry by rootNavController.currentBackStackEntryAsState()
                Scaffold(
                    bottomBar = {
                        NavigationBar {
                            items.forEach { item ->
                                // 这行代码通过将当前项的标题（转换为小写）与返回栈中当前目的地的路由进行比较来检查当前项是否被选中。如果它们匹配，则表示该项被选中。
                                val isSelected =
                                    item.title.lowercase() == navBackStackEntry?.destination?.route
                                NavigationBarItem(
                                    selected = isSelected,
                                    onClick = {
                                        // 执行的导航操作
                                        rootNavController.navigate(item.title.lowercase()) {
                                            /**
                                             * 这部分代码定义了导航时的返回栈行为。它指定了要弹出到的目标位置，即返回栈中的一个目的地。
                                             * 在这里，rootNavController.graph.findStartDestination().id找到了导航图的起始目的地，
                                             * 并将其作为弹出目标。
                                             */
                                            popUpTo(rootNavController.graph.findStartDestination().id) {
                                                // 表示弹出到目标位置时，保存目标位置及其状态
                                                saveState = true
                                            }
                                            // 如果导航目标已经在返回栈的栈顶，则不会创建一个新的实例，而是重用已存在的实例。
                                            launchSingleTop = true
                                            /**
                                             * 这个参数指定了在导航到目标时是否应该恢复目标的状态。
                                             * 如果目标之前已经被创建并保存了其状态，那么在导航到目标时会尝试恢复该状态。
                                             * 这对于保持导航目标的状态一致性很有用。
                                             */
                                            restoreState = true
                                        }
                                    },
                                    label = {
                                        Text(text = item.title)
                                    },
                                    icon = {
                                        Icon(
                                            imageVector = if (isSelected) item.selectedIcon else item.unselectedIcon,
                                            contentDescription = item.title
                                        )
                                    })
                            }
                        }
                    }
                ) { paddingValues ->
                    Box(modifier = Modifier.padding(paddingValues)) {
                        NavHost(navController = rootNavController, startDestination = "home"){
                            composable("home"){
                                HomeNavHost()
                            }
                            composable("chat"){
                                ChatNavHost()
                            }
                            composable("settings"){
                                SettingsNavHost()
                            }
                        }
                    }
                }
            }
```

## 构建host
```kotlin


@Composable
fun HomeNavHost() {
    val homeNavController = rememberNavController()
    NavHost(navController = homeNavController, startDestination = "home1"){
        for (i in 1..10){
            composable("home${i}"){
                GenericScreen(text = "Home${i}") {
                    if(i<10){
                        homeNavController.navigate("home${i+1}")
                    }
                }
            }
        }
    }
}

```

## 生成页面

```kotlin

@Composable
fun GenericScreen(text: String, onNextClick: () -> Unit) {
    Column(
        modifier = Modifier.fillMaxSize(),
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center
    ) {
        Text(text = text)
        Spacer(modifier = Modifier.height(16.dp))
        Button(onClick = onNextClick) {
            Text(text = "Next")
        }
    }
}
```

## 底部导航栏数据
```kotlin
data class BottomNavigationItem(
    val title: String,
    val unselectedIcon: ImageVector,
    val selectedIcon: ImageVector
)

val items = listOf(
    BottomNavigationItem(
        title = "Home",
        selectedIcon = Icons.Filled.Home,
        unselectedIcon = Icons.Outlined.Home
    ),
    BottomNavigationItem(
        title = "Chat",
        selectedIcon = Icons.Filled.Email,
        unselectedIcon = Icons.Outlined.Email
    ),
    BottomNavigationItem(
        title = "Settings",
        selectedIcon = Icons.Filled.Settings,
        unselectedIcon = Icons.Outlined.Settings
    )
)
```

## 底部导航栏的依赖
```kts
implementation("androidx.navigation:navigation-compose:2.7.5")
```