我们用google推荐的这种方式
修改：
StudentDao
package com.anguomob.jecpack.dao
import androidx.lifecycle.LiveData
import androidx.room.*
import com.anguomob.jecpack.bean.Student
@Dao
interface StudentDao {
@Insert
fun insertStudent(vararg student: Student)
@Delete
fun deleteStudent(vararg student: Student)
@Query("DELETE FROM student")
fun deleteAllStudent()
@Update
fun updateStudent(vararg student: Student)
@Query("SELECT * FROM student")
fun queryAllStudent(): LiveData<List<Student>>
@Query("SELECT * FROM student where id = :id")
fun getStudentById(id: Int): List<Student>
}
新增
StudentRepository类
package com.anguomob.jecpack.repository
import android.content.Context
import android.os.AsyncTask
import androidx.lifecycle.LiveData
import com.anguomob.jecpack.bean.Student
import com.anguomob.jecpack.dao.StudentDao
import com.anguomob.jecpack.database.MyDataBase
class StudentRepository(var context: Context) {
private lateinit var studentDao: StudentDao
init {
val dataBase = MyDataBase.getSingle(context)
this.studentDao = dataBase.getStudentDao();
}
fun insertStudent(vararg student: Student) {
InsertStudentTask(studentDao).execute(*student)
}
fun deleteStudent(vararg student: Student) {
DeleteStudentTask(studentDao).execute(*student)
}
fun updateStudent(vararg student: Student) {
UpdateStudentTask(studentDao).execute(*student)
}
fun queryAllStudent():LiveData<List<Student>> {
return studentDao.queryAllStudent()
}
fun deleteAllStudent() {
DeleteAllStudentTask().execute()
}
inner class InsertStudentTask(var studentDao: StudentDao) : AsyncTask<Student, Any, Any>() {
override fun doInBackground(vararg p0: Student) {
studentDao.insertStudent(*p0)
}
}
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)
}
}
inner class DeleteAllStudentTask() : AsyncTask<Any, Any, Any>() {
override fun doInBackground(vararg p0: Any) {
studentDao.deleteAllStudent()
}
}
}
新增
StudentViewModel
package com.anguomob.jecpack.viewmodel
import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import com.anguomob.jecpack.bean.Student
import com.anguomob.jecpack.repository.StudentRepository
class StudentViewModel(application: Application) : AndroidViewModel(application) {
private lateinit var repository: StudentRepository
init {
repository = StudentRepository(application)
}
fun insertStudent(vararg student: Student) {
repository.insertStudent(*student)
}
fun deleteStudent(vararg student: Student) {
repository.deleteStudent(*student)
}
fun updateStudent(vararg student: Student) {
repository.updateStudent(*student)
}
fun queryAllStudent(): LiveData<List<Student>> {
return repository.queryAllStudent()
}
fun deleteAllStudent() {
repository.deleteAllStudent()
}
}
修改页面代码
package com.anguomob.jecpack.activity
import android.annotation.SuppressLint
import android.os.AsyncTask
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.lifecycle.ViewModelProvider
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
import com.anguomob.jecpack.repository.StudentRepository
import com.anguomob.jecpack.viewmodel.StudentViewModel
class RoomActivity : AppCompatActivity() {
private lateinit var binding: ActivityRoomBinding
private lateinit var adapter: RoomAdapter
private lateinit var viewModel: StudentViewModel
@SuppressLint("NotifyDataSetChanged")
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;
viewModel =
ViewModelProvider(this, ViewModelProvider.AndroidViewModelFactory(application)).get(
StudentViewModel::class.java
);
viewModel.queryAllStudent().observe(this) { data ->
adapter.setData(data)
adapter.notifyDataSetChanged();
}
}
fun insert(view: View) {
val s1 = Student("Jack", 20)
val s2 = Student("Jack2", 21)
viewModel.insertStudent(s1, s2)
}
fun change(view: View) {
val s1 = Student(15, "LiuAn", 27)
val s2 = Student(16, "LiuAN2", 18)
viewModel.updateStudent(s1, s2)
}
fun delete(view: View) {
val s1 = Student(20)
viewModel.deleteStudent(s1)
}
fun clear(view: View) {
viewModel.deleteAllStudent()
}
}
布局文件把查询替换为了清空
<?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="clear"
android:text="清空"
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>
这种做法可以让数据自己展示出来。从而达到更加方便不用每次操作后手动去查询
非常的时尚
