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

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