如何解决无法从我的daoAndroid Room访问具有特定属性的元素
我正在与多个用户一起创建toDoList应用。我有两个实体。一个是用户,另一个是任务
@Entity(tableName = "tasks")
data class Task(
@PrimaryKey(autoGenerate = true)
val id : Int,val taskUserId : Int,val taskName : String,val taskDescription : String,var taskPriority : Int)
@Entity(tableName = "users")
data class User(
@PrimaryKey
val userId : Int,val userName : String,val password : String)
如您所见,这两个实体需要有一个共同点,那就是用户ID,因此我可以根据用户ID查询任务。这就是我的模样:
@Dao
interface UserDao {
@Query("SELECT * FROM users")
fun getAllUsers() : LiveData<List<User>>
@Query("SELECT * FROM tasks WHERE taskUserId LIKE :userId ORDER BY taskPriority DESC")
fun getAllUsersTasks(userId : Int) : LiveData<List<Task>>
@Insert
suspend fun saveUser(user : User)
@Insert
suspend fun saveTask(task : Task)
}
还有其他模型元素:
class TaskRepository(private val userDao: UserDao) {
var userId : Int = 0
val allTasks = userDao.getAllUsersTasks(userId)
val allUsers : LiveData<List<User>> = userDao.getAllUsers()
suspend fun saveUser(user : User){
userDao.saveUser(user)
}
suspend fun saveTask(task : Task){
userDao.saveTask(task)
}
}
和ViewModel:
class MainViewModel(application: Application) : AndroidViewModel(application) {
private val taskRepository : TaskRepository
val allTasks : LiveData<List<Task>>
val allUsers : LiveData<List<User>>
private var userId : Int = 0
init {
val taskDao = UserTasksDatabase.getDatabase(application)!!.userDao()
taskRepository = TaskRepository(taskDao)
allTasks = taskRepository.allTasks
allUsers = taskRepository.allUsers
taskRepository.userId = this.userId
}
fun saveUser(user: User) = viewModelScope.launch(Dispatchers.IO){
taskRepository.saveUser(user)
}
fun saveTask(task: Task) = viewModelScope.launch(Dispatchers.IO){
taskRepository.saveTask(task)
}
fun setUserId(id : Int){
this.userId = id
}
fun getUserId() : Int{
return this.userId
}
}
当用户按下登录名或注册按钮时,我在viewModel中设置了用户ID
logInButton.setOnClickListener {
val userName: String = userNameEditText.text.toString()
val password: String = passwordEditText.text.toString()
val id: Int = IdMaker.generateId(userName)
val user = User(id,userName,password)
if(listOfAllUsers.contains(user)){
sharedViewModel.setUserId(id)
Toast.makeText(requireContext(),"Welcome $userName",Toast.LENGTH_LONG).show()
fragmentManager!!.beginTransaction().apply {
replace(R.id.fl_activity_main,MainFragment())
commit()
}
}else{
Toast.makeText(requireContext(),"The user already exists",Toast.LENGTH_LONG).show()
}
}
但是当我尝试访问主片段中的用户并将它们设置在我的recyclerview上时,我什么也没得到。而且我真的看不到我在想什么。
sharedViewModel.allTasks.observe(this,Observer {tasks ->
tasks.let { adapter.setTasks(it) }
})
对于一个简单的问题,我们感到抱歉,但我希望我能对我所缺少的内容有所了解。
侧面说明:正确设置了recyclerview并对其进行了测试。
解决方法
我认为您没有正确设置TaskRepository.userId
。
class MainViewModel(application: Application) : AndroidViewModel(application) {
private val taskRepository : TaskRepository
private var userId : Int = 0
init {
...
// init is called only once at the start of this viewModel's instance creation
// Here,you set your repository's userId to 0
taskRepository.userId = this.userId
}
}
在创建MainViewModel
的实例时,将其userId
实例的TaskRepository
设置为0,在您的以下代码中不再更改。单击登录按钮后,您会致电:
sharedViewModel.setUserId(id)
但是该函数仅更改viewModel的userId
属性,而不更改您的userId
实例的TaskRepository
属性。所以尝试:
class MainViewModel(application: Application) : AndroidViewModel(application) {
private lateinit var taskRepository : TaskRepository
val allTasks = taskRepository.allTasks
val allUsers = taskRepository.allUsers
// remove init {}
fun setUserId(id : Int){
// set up the repository only after userId is known
val taskDao = UserTasksDatabase.getDatabase(application)!!.userDao()
taskRepository = TaskRepository(taskDao,id)
}
}
并更改您的TaskRepository
类:
class TaskRepository(private val userDao: UserDao,private val userId: Int) {
val allTasks: LiveData<List<Task>>
get() = userDao.getAllUsersTasks(userId)
val allUsers: LiveData<List<User>>
get() = userDao.getAllUsers()
...
}
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