# android_userList **Repository Path**: ZQY5678/android_userList ## Basic Information - **Project Name**: android_userList - **Description**: kotlin room数据库增删改查 - **Primary Language**: Unknown - **License**: Not specified - **Default Branch**: master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2021-11-18 - **Last Updated**: 2021-11-18 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # 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 ![userList](README.assets/userList.gif) ## 1. 添加依赖 注释使用`kapt` ```java 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 ```java 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:$lifecycle_version" ``` ### 1.2 Room + Room就好像spring中的jpa，让CRUD更简单 ```java def room_version = "2.2.5" implementation "androidx.room:room-runtime:$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 ```java // 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 ```java javaCompileOptions { annotationProcessorOptions { arguments = ["room.schemaLocation": "$projectDir/schemas".toString()] } } ``` ### 1.5 dataBinding + 需要在配置`android`中激活dataBinding ```java 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 ```java /** * @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 ```kotlin /** * @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> @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 ```kotlin 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 ```kotlin /** * @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： ```java 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 ```kotlin /** * @author: ffzs * @Date: 2020/9/11 下午4:46 */ class UserViewModel (private val repository: UserRepository): ViewModel(), Observable { @Bindable val inputName = MutableLiveData() @Bindable val inputEmail = MutableLiveData() @Bindable val btnSave = MutableLiveData() @Bindable val btnDel = MutableLiveData() ``` ### 3.2 activity_main绑定 + 通过layout进行绑定，使用`variable`进行配置 ![image-20200911183525276](README.assets/image-20200911183525276.png) ### 3.3 关联使用 + 变量关联 ![image-20200911183650914](README.assets/image-20200911183650914.png) + 函数关联，像极了前端的回调 ![image-20200911183735460](README.assets/image-20200911183735460.png) ### 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` ![image-20200911184101770](README.assets/image-20200911184101770.png) ### 3.5 ViewModelProvider.Factory ```kotlin /** * @author: ffzs * @Date: 2020/9/11 下午6:43 */ class UserViewModelFactory (private val repository: UserRepository): ViewModelProvider.Factory { override fun create(modelClass: Class): 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 ```java binding.lifecycleOwner = this ``` ### 3.7 完整绑定代码 ```kotlin 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 ```kotlin /** * @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 ```kotlin /** * @author: ffzs * @Date: 2020/9/11 下午7:11 */ class UserRecyclerViewAdapter(private val clickListener: (User) -> Unit) : RecyclerView.Adapter() { private val userList = ArrayList() 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){ 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 ```kotlin 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 ![image-20200911172648573](README.assets/image-20200911172648573.png) 配置中需要enable ```java 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 ![image-20200911185411607](README.assets/image-20200911185411607.png) ## 7. 源码 [github](https://github.com/ffzs/android_userList)