Android jetpack room+ViewModel+liveData 数据自动更新

Posted 2022-05-23 安果移不动

Android jetpack room的使用_安果移不动的博客-CSDN博客

接上篇博客

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