Android jetpack room的使用

做一个对学生表增删改查的小demo 来了解 一下room

 第一步 添加依赖

implementation 'androidx.room:room-runtime:2.4.2'
    kapt 'androidx.room:room-compiler:2.4.2'

 记得勾选kapt

第二步 创建javaBean

package com.anguomob.jecpack.bean

import androidx.room.ColumnInfo
import androidx.room.Entity
import androidx.room.Ignore
import androidx.room.PrimaryKey

@Entity(tableName = "student")
data class Student(
    @PrimaryKey(autoGenerate = true)
    @ColumnInfo(name = "id", typeAffinity = ColumnInfo.INTEGER)
    var id: Int,
    @ColumnInfo(name = "name", typeAffinity = ColumnInfo.TEXT)
    var name: String,
    @ColumnInfo(name = "age", typeAffinity = ColumnInfo.INTEGER)
    var age: Int
) {

    @Ignore
    constructor(name: String, age: Int) : this(0, name, age)


    @Ignore
    constructor(id: Int) : this(id, "",0)
}

这里呢。设置了自增id 又对每个属性针对数据库的字段做了标志

如果不需要某字段

可以使用@Ignore通配符

编写Dao类操作数据库

 

package com.anguomob.jecpack.dao

import androidx.room.*
import com.anguomob.jecpack.bean.Student

@Dao
interface StudentDao {
    @Insert
    fun insertStudent(vararg student: Student)

    @Delete
    fun deleteStudent(vararg student: Student)

    @Update
    fun updateStudent(vararg student: Student)


    @Query("SELECT * from student")
    fun queryAllStudent(): List<Student>

    @Query("SELECT * from student where id = :id")
    fun getStudentById(id: Int): List<Student>
}

编写

RoomDatabase 数据库类 来操作数据库对象

 

package com.anguomob.jecpack.database

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase
import com.anguomob.jecpack.bean.Student
import com.anguomob.jecpack.dao.StudentDao
import okhttp3.internal.Internal.instance

@Database(entities = [Student::class], version = 1, exportSchema = false)
abstract class MyDataBase : RoomDatabase() {
    companion object {
        var DATABASE_NAME = "my_db.db"
        private lateinit var instance: MyDataBase


        fun getSingle(context: Context): MyDataBase {
            if (::instance.isInitialized.not()) {
                instance = Room.databaseBuilder(
                    context.applicationContext,
                    MyDataBase::class.java,
                    DATABASE_NAME
                )
                    .allowMainThreadQueries()//允许主线程操作数据库
                    .build();
            }

            return instance;
        }
    }

    abstract fun getStudentDao(): StudentDao


}

编写页面布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.RoomActivity">

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.09165527" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.19015048" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.5" />

    <Button
        android:id="@+id/button5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="insert"
        android:text="增加"
        app:layout_constraintBottom_toTopOf="@+id/guideline5"
        app:layout_constraintEnd_toStartOf="@+id/guideline8"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button6"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="change"
        android:text="修改"
        app:layout_constraintBottom_toTopOf="@+id/guideline5"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline8"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="delete"
        android:text="删除"
        app:layout_constraintBottom_toTopOf="@+id/guideline7"
        app:layout_constraintEnd_toStartOf="@+id/guideline8"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline5" />

    <Button
        android:id="@+id/button8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="query"
        android:text="查询"
        app:layout_constraintBottom_toTopOf="@+id/guideline7"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline8"
        app:layout_constraintTop_toTopOf="@+id/guideline5" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rv"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline7" />
</androidx.constraintlayout.widget.ConstraintLayout>

main页面代码

package com.anguomob.jecpack.activity

import android.os.AsyncTask
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.recyclerview.widget.LinearLayoutManager
import com.anguomob.jecpack.R
import com.anguomob.jecpack.adapter.RoomAdapter
import com.anguomob.jecpack.bean.Student
import com.anguomob.jecpack.dao.StudentDao
import com.anguomob.jecpack.database.MyDataBase
import com.anguomob.jecpack.databinding.ActivityRoomBinding

class RoomActivity : AppCompatActivity() {
    private lateinit var binding: ActivityRoomBinding
    private lateinit var adapter: RoomAdapter
    private lateinit var dataBase: MyDataBase
    private lateinit var studentDao: StudentDao
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityRoomBinding.inflate(layoutInflater)
        setContentView(binding.root)
        binding.rv.layoutManager = LinearLayoutManager(this)
        adapter = RoomAdapter()
        binding.rv.adapter = adapter;
        dataBase = MyDataBase.getSingle(this)
        studentDao = dataBase.getStudentDao()
    }

    fun insert(view: View) {

        val s1 = Student("Jack", 20)
        val s2 = Student("Jack2", 21)
        //主线程直接插入
//        studentDao.insertStudent(s1)
        //切换到子线程插入
        InsertStudentTask(studentDao).execute(s1, s2)

    }

    fun change(view: View) {
        val s1 = Student(1, "LiuAn", 27)
        val s2 = Student(2, "LiuAN2", 27)
        //主线程直接插入
//        studentDao.insertStudent(s1)
        //切换到子线程插入
        UpDateStudentTask(studentDao).execute(s1, s2)

    }

    fun delete(view: View) {
        DeleteStudentTask(studentDao).execute(Student(1))

    }

    fun query(view: View) {
        GetAllStudentTask(studentDao).execute()
    }

    inner class InsertStudentTask(var studentDao: StudentDao) : AsyncTask<Student, Any, Any>() {
        override fun doInBackground(vararg p0: Student) {
            studentDao.insertStudent(*p0)
        }
    }

    inner class GetAllStudentTask(var studentDao: StudentDao) : AsyncTask<Any, Any, Any>() {
        override fun doInBackground(vararg p0: Any?) {
            val queryAllStudent = studentDao.queryAllStudent()
            adapter.setData(queryAllStudent);
        }

        override fun onPostExecute(result: Any?) {
            super.onPostExecute(result)
            adapter.notifyDataSetChanged()
        }

    }

    inner class UpDateStudentTask(var studentDao: StudentDao) : AsyncTask<Student, Any, Any>() {
        override fun doInBackground(vararg p0: Student) {
            studentDao.updateStudent(*p0)
        }
    }

    inner class DeleteStudentTask(var studentDao: StudentDao) : AsyncTask<Student, Any, Any>() {
        override fun doInBackground(vararg p0: Student) {
            studentDao.deleteStudent(*p0)
        }
    }

}

这里用到了Adapter

package com.anguomob.jecpack.adapter

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.recyclerview.widget.RecyclerView
import com.anguomob.jecpack.R
import com.anguomob.jecpack.bean.Idol2
import com.anguomob.jecpack.bean.Student
import com.anguomob.jecpack.databinding.ItemBinding
import com.anguomob.jecpack.databinding.ItemRoomBinding

class RoomAdapter : RecyclerView.Adapter<RoomAdapter.RoomViewHolder>() {
    var mData: MutableList<Student> = mutableListOf();
    lateinit var itemRoomBinding: ItemRoomBinding

    fun setData(data: List<Student>) {
        this.mData.clear()
        this.mData.addAll(data)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RoomViewHolder {
        itemRoomBinding = DataBindingUtil.inflate(
            LayoutInflater.from(parent.context),
            R.layout.item_room,
            parent,
            false
        )
        return RoomViewHolder(itemRoomBinding);

    }

    override fun onBindViewHolder(holder: RoomViewHolder, position: Int) {
        val data = mData.get(position);
        holder.itemBinding.student = data;
    }

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


    class RoomViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        lateinit var itemBinding: ItemRoomBinding

        constructor(itemBinding: ItemRoomBinding) : this(itemBinding.root) {
            this.itemBinding = itemBinding;
        }
    }
}

adapter布局代码

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <variable
            name="student"
            type="com.anguomob.jecpack.bean.Student" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="40dp">

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.7" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline9"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.3" />

        <TextView
            android:id="@+id/id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"

            android:text="@{String.valueOf(student.id)}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/guideline9"
            app:layout_constraintHorizontal_bias="0.46"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{student.name}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/guideline3"
            app:layout_constraintStart_toStartOf="@+id/guideline9"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/age"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(student.age)}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="@+id/guideline3"
            app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

我们虽然开启了主线程可以操作数据库 但是为了高效还是用内部类+

AsyncTask的方式抽取到了外面