2024/4/7

跟着教程写todoapplication：

room创建本地数据库：

package com.example.to_do_application.data

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase
import androidx.room.TypeConverters
import com.example.to_do_application.data.models.ToDoData

@Database(entities = [ToDoData::class], version = 1, exportSchema = false)
@TypeConverters(Converter::class)
abstract class ToDoDatabase: RoomDatabase() {
    abstract fun toDoDao(): ToDoDao
    companion object{
        @Volatile
        private var INSTANCE: ToDoDatabase? = null

        fun getDatabase(context: Context): ToDoDatabase{
            val tempInstance = INSTANCE
            if(tempInstance != null){
                return tempInstance
            }
            synchronized(this){
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    ToDoDatabase::class.java,
                    "todo_database"
                ).build()
                INSTANCE = instance
                return instance
            }
        }
    }
}

package com.example.to_do_application.data

import androidx.lifecycle.LiveData
import androidx.room.*
import com.example.to_do_application.data.models.ToDoData

@Dao
interface ToDoDao {

    @Query("SELECT * FROM todo_table ORDER BY id ASC")
    fun getAllData(): LiveData<List<ToDoData>>

    @Insert(onConflict = OnConflictStrategy.IGNORE)
    suspend fun insertData(toDoData: ToDoData)

    @Update
    suspend fun updateData(toDoData: ToDoData)

    @Delete
    suspend fun deleteItem(toDoData: ToDoData)

    @Query("DELETE FROM todo_table")
    suspend fun deleteAll()

    @Query("SELECT * FROM todo_table WHERE tile LIKE :searchQuery")
    fun searchDatabase(searchQuery: String): LiveData<List<ToDoData>>

    @Query("SELECT * FROM todo_table ORDER BY CASE WHEN priority LIKE 'H%' THEN 1 WHEN priority LIKE 'M%' THEN 2 WHEN priority LIKE 'L%' THEN 3 END")
    fun sortByHighPriority(): LiveData<List<ToDoData>>

    @Query("SELECT * FROM todo_table ORDER BY CASE WHEN priority LIKE 'L%' THEN 1 WHEN priority LIKE 'M%' THEN 2 WHEN priority LIKE 'H%' THEN 3 END")
    fun sortByLowPriority(): LiveData<List<ToDoData>>
}

package com.example.to_do_application.data

import androidx.room.TypeConverter
import com.example.to_do_application.data.models.Priority

class Converter {
    @TypeConverter
    fun fromPriority(priority: Priority): String{
        return priority.name
    }

    @TypeConverter
    fun toPriority(priority: String): Priority {
        return Priority.valueOf(priority)
    }
}

package com.example.to_do_application.data.viewmodel

import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import androidx.lifecycle.viewModelScope
import com.example.to_do_application.data.ToDoDatabase
import com.example.to_do_application.data.models.ToDoData
import com.example.to_do_application.data.respository.ToDoRepository
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch


class ToDoViewModel(application: Application): AndroidViewModel(application) {
    private val toDoDao = ToDoDatabase.getDatabase(application).toDoDao()
    private val repository: ToDoRepository

    val getAllData: LiveData<List<ToDoData>>
    val sortByHighPriority: LiveData<List<ToDoData>>
    val sortByLowPriority: LiveData<List<ToDoData>>


    init {
        repository = ToDoRepository(toDoDao)
        getAllData = repository.getAllData

        sortByHighPriority = repository.sortByHighPriority
        sortByLowPriority = repository.sortByLowhPriority
    }

    fun insertData(toDoData: ToDoData){
        viewModelScope.launch(Dispatchers.IO){
            repository.insertData(toDoData)
        }
    }

   fun updateData(toDoData: ToDoData){
       viewModelScope.launch(Dispatchers.IO){
           repository.updateData(toDoData)
       }
   }

    fun deleteData(toDoData: ToDoData){
        viewModelScope.launch(Dispatchers.IO){
            repository.deleteItem(toDoData)
        }
    }

    fun deletaAll(){
        viewModelScope.launch(Dispatchers.IO){
            repository.deleteAll()
        }
    }

    fun searchDatabase(searchQuery: String): LiveData<List<ToDoData>>{
        return repository.searchDatabase(searchQuery)
    }
}