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转载注明原文：android-Kotlin类型不匹配编译错误：要求成功,发现MyError - 代码日志

解决方法:

以下是Flowable中的相关声明,以供参考.让我们忽略onErrorReturn;这与这里的问题无关.

public Flowable<T> {
    public <R> Flowable<R> map(Function<? super T, ? extends R> mapper);
    public Flowable<T> startWith(T value);
}

这些是Kotlin推断的类型.

val upstream: Flowable<T>
val mapper:   (T) -> Success<T>    = { data -> Success(data) }
val map:      ((T) -> Success<T>) -> Flowable<Success<T>>
                                   = upstream::map
val mapped:   Flowable<Success<T>> = map(mapper)
val loading:  Loading              = Loading()
val startWith:
    (Success<T>) -> Flowable<Success<T>>
                                   = mapped::startWith

startWith(loading)  // type mismatch

更具体的Success T类型早已被推断出来,并且Kotlin不会回溯找到更通用的StateModel类型.为此,您可以手动声明类型,例如

// be explicit about the general type of the mapper
upstream.map { data -> Success(data) as StateModel }.startWith(Loading())

// be explicit about the generic type R = StateModel
upstream.map<StateModel> { data -> Success(data) }.startWith(Loading())

顺便说一句,您当前正在失去< T>在StateModel中.我建议更改基类以包括type参数.

sealed class StateModel<out T: Any>
object Loading : StateModel<nothing>()
data class Success<T: Any>(val data: T) : StateModel<T>()
data class MyError(val message: String) : StateModel<nothing>()

例如,这可以让您编写,

val <T: Any> StateModel<T>.data: T?
    get() = when (this) {
        is Success -> data
        else -> null
    }

Android & Kotlin：基于Room、Kotlin协程的MVVM app

本篇主要介绍Android系统通过Room进行CRUD操作，以及使用kotlin协程的处理方法。

0. 效果展示

1. 添加依赖

注释使用kapt

apply plugin: ''kotlin-kapt''

1.1 lifecycle

通过这个可以获取其他组建生命周期变化

• 这里注释使用kapt，选着相应的注释依赖

def lifecycle_version = "2.2.0"
// ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
// LiveData
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
// 基于kotlin-kapt的注释组建
kapt "androidx.lifecycle:lifecycle-compiler:$lifecycle_version"

1.2 Room

• Room就好像spring中的jpa，让CRUD更简单

def room_version = "2.2.5"
implementation "androidx.room:room-runtime:$room_version"
 // Kotlin 使用 kapt
kapt "androidx.room:room-compiler:$room_version" 

// optional - Kotlin Extensions and Coroutines support for Room 协程操作库
implementation "androidx.room:room-ktx:$room_version"

1.3 kotlin协程

• 添加coroutines依赖 以及 android协程依赖

// 添加协程安卓库
implementation ''org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.9''
implementation ''org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9''

1.4 数据库表导出

• 配置在defaultConfig中，将room.schemaLocation导出

javaCompileOptions {
   
   
    annotationProcessorOptions {
   
   
        arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]
    }
}

1.5 dataBinding

• 需要在配置android中激活dataBinding

dataBinding{
   
   
    enabled = true
}

2. 数据表实现

跟spring的配置差不多，model，dao，sersice这些

2.1 创建一个User类

• User类 对应到user_table
• @PrimaryKey设置主键先当于spring的@Id，autoGenerate = true设置自增
• @ColumnInfo(name = "user_name")指定列名

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午5:05
 */
@Entity(tableName = "user_table")
data class User (

    @PrimaryKey(autoGenerate = true)
    var id:Long,
    @ColumnInfo(name = "user_name")
    var name:String,
    @ColumnInfo(name = "email")
    var email:String
)

2.2 dao实现

• @Dao进行注释
• @Query写法跟jpa基本相同

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午5:08
 */

@Dao
interface UserDao {
   
   

    @Insert
    suspend fun insert (user: User):Long

    @Update
    suspend fun update (user: User):Int

    @Delete
    suspend fun delete (user: User):Int

    @Query("DELETE FROM user_table")
    suspend fun deleteAll ():Int

    @Query("SELECT * FROM user_table")
    fun findAll ():LiveData<List<User>>

    @Query("SELECT * FROM user_table WHERE id = :id")
    suspend fun findById (id:Long):User

}

2.3 服务实现

• 主要用来获取数据

class UserRepository(private val dao: UserDao) {
   
   

    val subscribers = dao.findAll()

    suspend fun insert(user: User):Long{
   
   
        return dao.insert(user)
    }

    suspend fun update(user: User):Int{
   
   
        return dao.update(user)
    }

    suspend fun delete(user: User) : Int{
   
   
        return dao.delete(user)
    }

    suspend fun deleteAll() : Int{
   
   
        return dao.deleteAll()
    }
}

2.4 RoomDatabase实现

• 通过伴生对象实现单例模式
• entities = [User::class]，需要实现表的类，通过反射生成数据表

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午5:15
 */
@Database(entities = [User::class], version = 1)
abstract class UserDatabase : RoomDatabase() {
   
   

    abstract val userDao: UserDao

    // 通过伴生对象实现单例模式
    companion object {
   
   
        @Volatile
        private var INSTANCE: UserDatabase? = null
        fun getInstance(context: Context): UserDatabase {
   
   
            synchronized(this) {
   
   
                var instance = INSTANCE
                if (instance == null) {
   
   
                    instance = Room.databaseBuilder(
                        context.applicationContext,
                        UserDatabase::class.java,
                        "user_table"
                    ).build()
                }
                return instance
            }
        }
    }
}

• 直接通过getInstance方法获取database实例：

UserDatabase.getInstance(application)

3. databinding实现

3.1 实现ViewModel

• 首先需要实现一个ViewModel，用来绑定参数

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午4:46
 */
class UserViewModel (private val repository: UserRepository): ViewModel(), Observable {
   
   
    @Bindable
    val inputName = MutableLiveData<String>()
    @Bindable
    val inputEmail = MutableLiveData<String>()
    @Bindable
    val btnSave = MutableLiveData<String>()
    @Bindable
    val btnDel = MutableLiveData<String>()

3.2 activity_main绑定

• 通过layout进行绑定，使用variable进行配置

3.3 关联使用

• 变量关联

• 函数关联，像极了前端的回调
  
  

3.4 绑定

• 通过下图的方法可以进行绑定，如图所示这里还少一个factory
  
  

3.5 ViewModelProvider.Factory

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午6:43
 */
class UserViewModelFactory (private val repository: UserRepository): ViewModelProvider.Factory {
   
   

    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
   
   
        if(modelClass.isAssignableFrom(UserViewModel::class.java)){
   
   
            return UserViewModel(repository) as T
        }
        throw IllegalArgumentException("ViewModel类型不匹配")
    }
}

3.6 设置生命周期的归属

• 指定binding的归属

binding.lifecycleOwner = this

3.7 完整绑定代码

val dao = UserDatabase.getInstance(application).userDao
val repository = UserRepository(dao)
binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
userViewModel = ViewModelProvider(this,UserViewModelFactory(repository)).get(UserViewModel::class.java)
binding.userViewModel = userViewModel

4. RecyclerView实现用户展示

4.1 Holder实现

• 将传入的user信息通过binding写到RecyclerView中
• 以及点击触发效果

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午7:12
 */
class UserViewHolder (val binding: UserListBinding): RecyclerView.ViewHolder(binding.root){
   
   

    fun bind(user: User, clickListener:(User)->Unit){
   
   
        binding.nameTextView.text = user.name
        binding.emailTextView.text = user.email
        binding.listItemLayout.setOnClickListener{
   
   
            clickListener(user)
        }
    }
}

4.2 Adapter实现

用来实现RecyclerView状态的更改

• 通过binding生成holder
• onBindViewHolder操作当前位置元素，并执行操作
• getItemCount返回展示数量

/**
 * @author: ffzs
 * @Date: 2020/9/11 下午7:11
 */
class UserRecyclerViewAdapter(private val clickListener: (User) -> Unit) : RecyclerView.Adapter<UserViewHolder>() {
   
   
    
    private val userList = ArrayList<User>()

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
   
   
        val layoutInflater = LayoutInflater.from(parent.context)
        val binding : UserListBinding =
            DataBindingUtil.inflate(layoutInflater,R.layout.user_list,parent,false)
        return UserViewHolder(binding)
    }

    override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
   
   
        holder.bind(userList[position], clickListener)
    }

    override fun getItemCount(): Int {
   
   
        return userList.size
    }

    fun setList(users: List<User>){
   
   
        userList.clear()
        userList.addAll(users)
    }
}

5. 协程使用

• insert协程写法，直接通过viewModelScope调用协程launch，在代码块中进行操作
• 感觉跟使用reactor有些相似，主要避免阻塞，dao中使用suspend标注异步

private fun insert(subscriber: User) = viewModelScope.launch {
   
   
    val newRowId = repository.insert(subscriber)
    if (newRowId > -1) {
   
   
        msg.value = Event("$newRowId 成功添加")
    } else {
   
   
        msg.value = Event("添加出错")
    }
}

6. debug

6.1 databinding载入失败

配置中需要enable

dataBinding{
   
   
    enabled = true
}

6.2 javax/xml/bind/JAXBException

• java8以上不自带xml bind下图中位置改成java8
• java11写spring还可以，看来写java还有点早
  
  

7. 源码

github

android -------- Retrofit + RxJava2.0 + Kotlin + MVP 开发的 WanAndroid 项目

简介

wanandroid 项目基于 Retrofit + RxJava2.0 + Kotlin + MVP

  implementation ''io.reactivex.rxjava2:rxjava:2.1.3''
    implementation ''com.squareup.retrofit2:retrofit:2.3.0''
    implementation ''com.squareup.retrofit2:converter-gson:2.3.0''
    implementation ''com.squareup.retrofit2:adapter-rxjava2:2.3.0''
    implementation ''io.reactivex.rxjava2:rxandroid:2.0.1''
    implementation ''com.github.bumptech.glide:glide:3.7.0''

    implementation ''cn.bingoogolapple:bga-banner:2.2.4''
    implementation ''com.just.agentweb:agentweb:1.0.3''

    /** loading状态组件 **/
    implementation ''com.github.ybq:Android-SpinKit:1.1.0''

    /**状态栏**/
    implementation ''com.gyf.barlibrary:barlibrary:2.3.0''

    implementation ''com.hyman:flowlayout-lib:1.1.2''

    implementation ''com.alibaba:fastjson:1.1.68.android''

有下拉刷新 SmartRefreshLayout

效果图      

玩 Android 的 Api 是免费的，感谢 WanAndroid 提供的数据来源

鸿洋大佬提供的 API 接口 http://www.wanandroid.com/blog/show/2

项目地址: https://github.com/DickyQie/wanandroid

Android Kotlin RXKotlin Room - 错误 Kotlin.unit

fun defaultDataCategory() : ArrayList<CategoryModel>{
        var cat: CategoryModel
        var catArrayList: ArrayList<CategoryModel> = ArrayList(0)
        val date: Int = Calendar.DATE
        val formatedDate = SimpleDateFormat("yyyy-MM-dd").format(Date())
        val formatedTime = SimpleDateFormat("HH:mm").format(Date())
        val DateTime = "$formatedDate  $formatedTime"

        catArrayList.add(
            CategoryModel(
                1,"Personal",true,"Red",Converter.toDate(Calendar.getInstance().timeInMillis),"system","system"
            )
        )

        catArrayList.add(
            CategoryModel(
                2,"Work","Blue","system"
            )
        )

        catArrayList.add(
            CategoryModel(
                3,"Home","Purple","system"
            )
        )

        catArrayList.add(
            CategoryModel(
                4,"Learn","Yellow","system"
            )
        )
       return catArrayList
    }

var catArrayList: ArrayList<CategoryModel> = DefaultData.defaultDataCategory()

        catArrayList.toObservable()
            .subscribeBy(  // named arguments for lambda Subscribers
                onNext = { homeviewmodel.insertCategory(it) },onError = { Log.e("error insert=",it.printstacktrace().toString()) },onComplete = { Log.e("complete insert=","complete insert") }
            )

FAILED: out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy 
/bin/bash -c "(out/host/linux-x86/bin/secilc -M true -G -c 30 out/target/product/hon450/obj/ETC/plat_sepolicy.cil_intermediates/plat_sepolicy.cil out/target/product/hon450/obj/ETC/27.0.cil_intermediates/27.0.cil out/target/product/hon450/obj/ETC/nonplat_sepolicy.cil_intermediates/nonplat_sepolicy.cil -o out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy.tmp -f /dev/null ) && (out/host/linux-x86/bin/sepolicy-analyze out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy.tmp permissive > out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy.permissivedomains ) && (if [ \"userdebug\" = \"user\" -a -s out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy.permissivedomains ]; then               echo \"==========\" 1>&2;               echo \"ERROR: permissive domains not allowed in user builds\" 1>&2;              echo \"List of invalid domains:\" 1>&2;                 cat out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy.permissivedomains 1>&2;            exit 1;                 fi ) && (mv out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy.tmp out/target/product/hon450/obj/ETC/sepolicy_intermediates/sepolicy )"
neverallow check failed at out/target/product/hon450/obj/ETC/nonplat_sepolicy.cil_intermediates/nonplat_sepolicy.cil:4181
  (neverallow base_typeattr_49_27_0 netd_27_0 (unix_stream_socket (connectto)))
    <root>
    allow at out/target/product/hon450/obj/ETC/nonplat_sepolicy.cil_intermediates/nonplat_sepolicy.cil:7695
      (allow WifiLogger_app netd_27_0 (unix_stream_socket (connectto)))

neverallow check failed at out/target/product/hon450/obj/ETC/plat_sepolicy.cil_intermediates/plat_sepolicy.cil:4696 from system/sepolicy/public/domain.te:586
  (neverallow base_typeattr_49 netd (unix_stream_socket (connectto)))
    <root>
    allow at out/target/product/hon450/obj/ETC/nonplat_sepolicy.cil_intermediates/nonplat_sepolicy.cil:7695
      (allow WifiLogger_app netd_27_0 (unix_stream_socket (connectto)))

Failed to generate binary 

net_domain(WifiLogger_app)	
unix_socket_connect(WifiLogger_app, netd, netd);