Jetpack Compos一些三方库的使用

ViewModel

库的引入

implementation "androidx.compose.runtime:runtime-livedata:1.5.0-alpha01"
implementation "androidx.lifecycle:lifecycle-viewmodel-compose:2.6.1"

viewModel横竖屏切换使内容保持不变

@Composable
fun One() {
    val viewModel: OneViewModel = viewModel(factory = OneViewModelFactory(0))
    val count by viewModel.count.observeAsState(0)
    Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally,
    ) {
        Text(count.toString(), modifier = Modifier.padding(10.dp))
        Button(
            onClick = {
                viewModel.onCountChanged(count + 1)
            },
            colors = ButtonDefaults.buttonColors(
                containerColor = Color.Blue
            ),
        ) {
            Text("Add Count")
        }
    }
}

 自定义OneViewModel.kt动态数据类

import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider

/**
 * created by cwj on 2023-12-25
 * Description:
 */
class OneViewModel(defaultCount: Int) : ViewModel() {

    private val _count = MutableLiveData(defaultCount)

    val count: LiveData get() = _count

    fun onCountChanged(count: Int) {
        _count.postValue(count)
    }
}

class OneViewModelFactory(private val defaultCount: Int) : ViewModelProvider.Factory {

    override fun  create(modelClass: Class): T {
        return OneViewModel(defaultCount) as T
    }
}

viewModel实现重启应用内容不清理(SharedPreferences数据保存，重启获取)

@Composable
fun Two() {
    val context = LocalContext.current
    val sp = context.getSharedPreferences("count_file", Context.MODE_PRIVATE)
    val defaultCount = sp.getInt("DEFAULT_COUNT", 0)
    val viewModel: OneViewModel = viewModel(factory = OneViewModelFactory(defaultCount))
    val count by viewModel.count.observeAsState(defaultCount)
    Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally,
    ) {
        Text(count.toString(), modifier = Modifier.padding(10.dp))
        Button(
            onClick = {
                val counts = count + 1
                viewModel.onCountChanged(counts)
                sp.edit {
                    putInt("DEFAULT_COUNT", counts)
                }
            },
            colors = ButtonDefaults.buttonColors(
                containerColor = Color.Blue
            ),
        ) {
            Text("Add Count")
        }
        Button(
            onClick = {
                sp.edit().clear().apply()
                viewModel.onCountChanged(0)
            },
            modifier = Modifier.padding(10.dp),
            colors = ButtonDefaults.buttonColors(
                containerColor = Color.Blue
            ),
        ) {
            Text("Clear Count")
        }
    }
}

Navigation

库的引入

//Navigation页面跳转库
implementation "androidx.navigation:navigation-compose:2.6.0-alpha08"
//gson数据解析库
implementation 'com.google.code.gson:gson:2.8.9'

Navigation跳转页面传参

/**
 *  Navigation实现页面跳转
 */
@Composable
fun NavigationTest(
    //开始页面
    startDestination: String = "one_page"
) {
    val navController = rememberNavController()

    NavHost(
        navController = navController,
        startDestination = startDestination
    ) {
        composable("one_page") {
            OnePage(navController)
        }
        composable(
            "two_page/{name}/{age}?hobby={hobby}/{people}",
            //定义参数类型，不定义默认字符串，Int类型的会解析有问题
            arguments = listOf(
                navArgument("name") { type = NavType.StringType },
                navArgument("age") { type = NavType.IntType },
                //添加可选参数
                navArgument("hobby") {
                    type = NavType.StringType
                    defaultValue = "打篮球"
                },
                //添加实体类参数
                navArgument("people") { type = NavType.StringType },
            ),
        ) {
            val defaultPeople = it.arguments?.getString("people", "") ?: ""
            val people = Gson().fromJson(defaultPeople, People::class.java)
            TwoPage(
                navController,
                it.arguments?.getString("name", "") ?: "",
                it.arguments?.getInt("age") ?: 0,
                it.arguments?.getString("hobby", "") ?: "",
                people
            )
        }
    }
}

/**
 * 页面二
 */
@Composable
fun TwoPage(
    navController: NavHostController,
    name: String,
    age: Int,
    hobby: String,
    people: People
) {
    Column(
        modifier = Modifier
            .fillMaxSize(),
    ) {
        Row(
            modifier = Modifier
                .fillMaxWidth()
                .background(Color.White),
            verticalAlignment = Alignment.CenterVertically
        ) {
            Image(
                modifier = Modifier
                    .padding(5.dp)
                    .clickable {
                        //返回上个页面
                        navController.navigateUp()
                    },
                painter = painterResource(id = R.drawable.back),
                contentDescription = "",
            )
            Text(
                text = "TwoPage",
                modifier = Modifier
                    .fillMaxWidth()
                    .padding(5.dp),
            )
        }

        Text(
            modifier = Modifier
                .fillMaxWidth()
                .padding(10.dp),
            text = "${name}今年${age}岁,爱好${hobby}\n" +
                    "${people.name}今年${people.age}岁，爱好${people.hobby}",
            textAlign = TextAlign.Center,
        )
    }
}

/**
 * 页面一
 */
@Composable
fun OnePage(navController: NavHostController) {
    val people = People("李四", 20, "打游戏")
    val gson = Gson().toJson(people)

    Column(
        modifier = Modifier
            .fillMaxSize(),
    ) {
        Text(
            text = "OnePage",
            textAlign = TextAlign.Center,
            modifier = Modifier
                .fillMaxWidth()
                .background(Color.White)
                .padding(5.dp),
        )

        Button(
            modifier = Modifier.padding(10.dp),
            onClick = {
                //跳转到TwoPage页面
                navController.navigate("two_page/张三/18?hobby=打乒乓球/$gson")
            },
            colors = ButtonDefaults.buttonColors(
                containerColor = Color.Blue
            )
        ) {
            Text(
                text = "点击跳转到下个页面",
            )
        }
    }
}

startDestination属性设置开始页面，composable中route属性设置跳转页面路由及传参，arguments给参数定义数据类型。

跳转页面用navController.navigate并添加路由及传参数据。

返回上个页面用navController.navigateUp()。

People.kt实体类

data class People(val name: String, val age: Int, val hobby: String)