实现一个简单的拉取网络todo app

思考怎么去做一个网络api的调取, 然后展示到android前端

需求分析

0. 考虑几个页面,页面展示什么内容
1. 我需不需要更改后端内容, 如果只是单纯的获取数据,那就只需考虑GET data
2. 如果我需要更改后端数据库的内容, 那么什么参数和什么事件将会导致我这样做
3. 考虑怎么配置网络请求, 网络请求返回的数据要不要存入到数据库
4. 如果要存入到数据库,那么数据项目的配置是怎么样的
5. 没有网络的情况下还能不能直接去拿到已经存在数据库的内容
6. 考虑适配的android平台, 这里以android 13 api 33 为例

实现一个从网络请求获取todo数据,展示在app上面

先任务简单化(注意使用到viewbinding，可能部分代码需要配合xml文件名具体分析)

// 依赖
implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0'

implementation 'com.drakeet.multitype:multitype:4.3.0'
def activity_version = "1.9.2"
// Kotlin
implementation "androidx.activity:activity-ktx:$activity_version"

def room_version = "2.4.2"
//room
implementation "androidx.room:room-ktx:$room_version"
implementation "androidx.room:room-runtime:$room_version"
//    kapt "androidx.room:room-compiler:$room_version"
ksp "androidx.room:room-compiler:$room_version"

// 奔溃阻止
implementation 'com.github.alhazmy13:Catcho:v1.1.0'

// ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.6.1"


implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4"
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4'
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
implementation 'com.squareup.okhttp3:logging-interceptor:4.9.3'
implementation 'com.squareup.okhttp3:okhttp:4.9.3'
implementation 'com.google.code.gson:gson:2.8.9'

// ksp插件配置, app模块
plugins {
    alias(libs.plugins.android.application)
    alias(libs.plugins.kotlin.android)

//    id 'kotlin-kapt'
    id 'com.google.devtools.ksp'
}

// 项目根
plugins {
    alias(libs.plugins.android.application) apply false
    alias(libs.plugins.kotlin.android) apply false
    // https://mvnrepository.com/artifact/com.google.devtools.ksp/symbol-processing
    //runtimeOnly 'com.google.devtools.ksp:symbol-processing:1.9.24-1.0.20'
    id 'com.google.devtools.ksp' version '1.9.24-1.0.20' apply false
}

1.配置BASE_URL

• private const val BASE_URL = "https://7ce074a2.r7.cpolar.top"

2. 配置好mongodb connect string后, 启动后端

• go run main.go

3. 找到需要的接口

• GET api/todos 是我需要的
• 接口返回示例

HTTP/1.1 200 OK
Date: Fri, 21 Feb 2025 07: 58: 10 GMT
Content-Type: application/json
Content-Length: 418
Vary: Origin
Connection: close

[
{
"_id": "67b8244a6d9be942d1ba3a8a",
"completed": true,
"body": "hello world"
},
{
"_id": "67b825616d9be942d1ba3a8b",
"completed": true,
"body": "Damn"
},
{
"_id": "67b828926d9be942d1ba3a8c",
"completed": true,
"body": "哈哈"
},
{
"_id": "67b829796d9be942d1ba3a8d",
"completed": true,
"body": "AAA"
},
{
"_id": "67b829896d9be942d1ba3a8e",
"completed": true,
"body": "你好呀"
},
{
"_id": "67b82da36d9be942d1ba3a8f",
"completed": true,
"body": "及你太美"
}
]

4. 编写接口

interface TodoApi {
    @GET("api/todos")
    suspend fun getAllTodos(): Response<List<Todo>>
}

5. 编写retrofit客户端

object ApiService {
    // todo: 如果是retrofit 的话，这个连接不生效就马上闪退
    // 后端链接:  https://gitee.com/EEPPEE_admin/probe-examples/tree/master/fiber-and-react-example/backend
    // 配合内网穿透工具cpolar使用
    // cmd: cpolar 6969
    private const val BASE_URL = "https://7ce074a2.r7.cpolar.top"

    val todoApi: TodoApi by lazy {
        Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build()
            .create(TodoApi::class.java)
    }
}

6. 数据库内容项保存

// 本机要存的信息
@Entity(
    tableName = "todos",
)
data class Todo(
    @PrimaryKey(autoGenerate = true)
    val id: Int = 0,
//    @PrimaryKey(autoGenerate/ = false)
    val _id: String = "",
    val completed: Boolean,
    val body: String,
)

7.dao查询接口

@Dao
interface TodoDao {
    @Query("SELECT * FROM todos")
    suspend fun getAllTodos(): List<Todo>
}

8. 数据库需要

@Database(
    entities = [
        Todo::class
    ],
    version = 1,
    exportSchema = false
)
abstract class TodoDB : RoomDatabase() {
    abstract fun todoDao(): TodoDao

    companion object {
        @Volatile
        private var instance: TodoDB? = null

        fun getDatabase(context: Context): TodoDB {
            return instance ?: Room.databaseBuilder(
                context.applicationContext,
                TodoDB::class.java,
                "todo_database"
            ).build()
            instance = instance
            instance
        }
    }
}

9. viewmodel层怎么搞,我也不会

class TodoViewModel(
    // 1. 需要注入网络api
    private val api: TodoApi,
    // 2. 需要注入本机数据库
    private val db: TodoDB
) : ViewModel() {
    fun getAllTodos() {
        viewModelScope.launch {
            val response = api.getAllTodos()
            Log.d("GET返回", response.body().toString())
            if (response.isSuccessful && response.body() != null) {
                // 拿到api的返回，然后存入数据库
                Log.d("GET响应", response.body().toString())
                response.body()!!.forEach { it ->
                    // 实际交付到dao做实际插入
                    db.todoDao().insertTodo(it)
                }
            }
        }
    }
}

// 还需要一个工厂？

10. 造一个activity和xml文件

• TodoActivity.kt
• activity_todo.xml: 需要刷新layout,和recyclerview

<?xml version="1.0" encoding="utf-8"?>
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/swiperefreshlayout"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:orientation="vertical">


    <androidx.recyclerview.widget.RecyclerView android:id="@+id/recyclerView"
        android:layout_width="match_parent" android:layout_height="match_parent" />
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>

• item_todo.xml: recyclerview里面的数据项

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:orientation="vertical" android:padding="16dp">

    <TextView android:id="@+id/tvTitle" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:text="Todo Title" android:textSize="18sp" />

    <TextView android:id="@+id/tvCompleted" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:text="Completed" android:textSize="14sp" />
</LinearLayout>

11. 为recyclerview编写一个adapter,这里使用MultiType库

class TodoItemViewBinder : ItemViewBinder<Todo, TodoItemViewBinder.ViewHolder>() {
    // 内部类
    inner class ViewHolder(
        private val binding: ItemTodoBinding // 绑定到item_todo.xml
    ) : RecyclerView.ViewHolder(binding.root) {
        fun bind(todo: Todo) {
            // 绑定效果
            binding.tvTitle.text = todo.body
            binding.tvCompleted.text = if (todo.completed) "已完成" else "暂时没搞定"
        }
    }

    override fun onBindViewHolder(holder: ViewHolder, item: Todo) {
        holder.bind(item)
    }

    override fun onCreateViewHolder(inflater: LayoutInflater, parent: ViewGroup): ViewHolder {
        val binding = ItemTodoBinding.inflate(inflater, parent, false)
        return ViewHolder(binding)
    }
}

12. 来实操TodoActivity.kt, 始终应该继承app compat activity，主要看onCreate内容就行

class TodoActivity : AppCompatActivity() {
    // 需要一个MultiTypeAdapter 对象
    private var multitypeAdapter = MultiTypeAdapter()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // 这里使用到viewbinding内容, 绑定到activity_todo.xml
        binding = ActivityTodoBinding.inflate(layoutInflater)
        // 配置奔溃阻止，使用到BuildConfig,需要配置build.gradle
        if (!com.example.myapplication.BuildConfig.IS_DEBUG) {
            setUpCatcho(this)
        }
        setContentView(binding.root)

        // 默认就加载网络数据
        loadTodos()

        // 实现下拉刷新,加载网络数据
        binding.swiperefreshlayout.setOnRefreshListener {
            loadTodos()
//            binding.swiperefreshlayout.isRefreshing = false
        }


        binding.recyclerView.layoutManager = LinearLayoutManager(this)
        binding.recyclerView.adapter = multitypeAdapter

        // 注册 Todo 类型及其 ItemViewBinder
        multitypeAdapter.register(Todo::class.java, TodoItemViewBinder())
    }
}

13.抽离出loadTodos,设置一个私有函数(没调试成功)

  private fun loadTodos() {
    MainScope().launch {
        try {
            if (NetworkCheckConnUtil.isNetworkAvailable(this@TodoActivity)) {
                // 网络可用
                val response = ApiService.todoApi.getAllTodos()
                if (response.isSuccessful && response.body() != null) {
                    val todos = response.body()!!
                    // 插入到数据库
                    todos.forEach { it ->
                        todoDB?.todoDao()
                            ?.insertTodo(it)
                    }

                    multitypeAdapter.items = todos
                    multitypeAdapter.notifyDataSetChanged()
                    binding.recyclerView.adapter = multitypeAdapter
                }
            } else {
                Toast.makeText(this@TodoActivity, "网络不可用", Toast.LENGTH_SHORT)
                    .show()
                loadTodosFromDatabase()
            }
        } catch (e: Exception) {
            e.printStackTrace()
            Toast.makeText(this@TodoActivity, "网络不可用", Toast.LENGTH_SHORT)
                .show()
            loadTodosFromDatabase()
        } finally {
            binding.swiperefreshlayout.isRefreshing = false
        }
    }
}

遇到的问题（以上内容有修改了，看源码为主）

1. retrofit无网络，或者base url配置错时， 程序会闪退，这个东西要额外在viewmodel层处理

• ok,解决bug的逻辑是这样，一开始就加载本地数据库内容（然后土司网络不可用)，知道下滑刷新才加载网络内容，how
  about that
• 程序一开始就没网的时候就闪退，我解决不了

总结

• 实现刷新加载网络数据成功
• 但是没有实现从数据库中获取内容，调试不通，无网络时，会报错误

java.net.UnknownHostException: Unable to resolve host "7ce074a2.r7.cpolar.top": No address associated with hostname
at 

• 写shitcode啊,写安卓没有思路

效果截图

ref link:

• https://gitee.com/EEPPEE_admin/android-mono-repo/tree/aaa/app/src/main/java/com/example/myapplication/todoapp
• 后端: https://gitee.com/EEPPEE_admin/probe-examples/tree/master/fiber-and-react-example/backend