使用Dao数据库创建viewmodel导致的错误

问题描述

我尝试在我的应用程序中使用 dao 数据库，但当我尝试创建视图模型时出现此错误：

E/libc：访问被拒绝，发现属性“ro.vendor.df.effect.conflict” E/Perf：无法获取文件列表 com.example.kiedyssieuda E/Perf: getFolderSize() : Exception_1 = java.lang.NullPointerException: 尝试获取空数组的长度 E/Perf：无法获取文件列表 com.example.kiedyssieuda getFolderSize() : Exception_1 = java.lang.NullPointerException: 尝试获取空数组的长度

人物类：

@Entity(tableName = "people_table")
data class Person(var name: String,var surname: String ){
    @PrimaryKey(autoGenerate = true)
    var user_id: Int = 0
}

人道界面

@Dao
interface PeopleDao {
    @Insert
    fun insert(person: Person)

    @Update
    fun update(person: Person)

    @Delete
    fun delete(person: Person)

    @Query("SELECT * FROM people_table")
    fun getAllPeople(): LiveData<List<Person>>

    @Query("DELETE FROM people_table")
    fun deleteallRows()
}

PeopleDatabase 抽象类

@Database(entities = [Person::class],version = 1,exportSchema = false)
abstract class PeopleDatabase : RoomDatabase(){

    abstract fun peopleDao(): PeopleDao

    companion object{
        private var instance: PeopleDatabase? =null

        fun getInstance(context: Context): PeopleDatabase?{
            if (instance==null){
                instance = Room.databaseBuilder(
                    context,PeopleDatabase::class.java,"people_table")
                    .fallbackToDestructiveMigration()
                    .build()
            }
            return instance
        }
        fun deleteInstanceOfDatabase(){
            instance=null
        }
    }
}

PeopleRepository 类

class PeopleRepository(application: Application) {
    private var peopleDao: PeopleDao
    init {
        val database:PeopleDatabase? = PeopleDatabase
            .getInstance(application.applicationContext)

        peopleDao = database!!.peopleDao()
    }
    fun insertPerson (person: Person): Job =
        Coroutinescope(dispatchers.IO).launch {
            peopleDao.insert(person)
        }
    fun uptadePerson (person: Person): Job =
        Coroutinescope(dispatchers.IO).launch {
            peopleDao.update(person)
        }
    fun deletePerson(person: Person): Job =
        Coroutinescope(dispatchers.IO).launch {
            peopleDao.delete(person)
        }
    fun getAllPeopleAsync(): Deferred<LiveData<List<Person>>> =
        Coroutinescope(dispatchers.IO).async {
            peopleDao.getAllPeople()
        }
    fun deleteallRows(): Job =
        Coroutinescope(dispatchers.IO).launch {
            peopleDao.deleteallRows()
        }

Peopleviewmodel 类

class Peopleviewmodel(application: Application):
    Androidviewmodel(application) {

    private var peopleRepository: PeopleRepository =
        PeopleRepository(application)

    private var allPeople: Deferred<LiveData<List<Person>>> =
        peopleRepository.getAllPeopleAsync()

    fun insertPerson(person: Person){
        peopleRepository.insertPerson(person)
    }
    fun uptadePerson(person: Person){
        peopleRepository.uptadePerson(person)
    }
    fun deletePerson(person: Person){
        peopleRepository.deletePerson(person)
    }
    fun getAllPeople(): LiveData<List<Person>> = runBlocking {
        allPeople.await()
    }
    fun deleteallRows(){
        peopleRepository.deleteallRows()
    }
}

主要活动：

class MainActivity : AppCompatActivity() {
    private lateinit var viewmodel: Peopleviewmodel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val users = ArrayList<Person>()
        //users.add(Person("abc","123"))

           viewmodel = viewmodelProvider
               .AndroidviewmodelFactory
               .getInstance(application)
               .create(Peopleviewmodel::class.java)
    }
}

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

如果你已经找到好的解决方法，欢迎将解决方案带上本链接一起发送给小编。

小编邮箱:dio#foxmail.com (将#修改为@）