Android : Room 数据库的基本用法 —简单应用_一_入门 - ToB企服应用市场:ToB评测及商务社交产业平台

dependencies {
//Room
def room_version = "2.5.0"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"
}

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package com.example.myroom.entity;
import androidx.room.ColumnInfo;
import androidx.room.Entity;
import androidx.room.PrimaryKey;
//实体类表名不写默认内名首字母小写 people
@Entity(tableName = "people")
public class People {
//主键自动生成
@PrimaryKey(autoGenerate = true)
private int id;
//列的名称
@ColumnInfo(name = "user_name")
private String name;
//不写默认列的名称为age，sex
private int age;
private String sex;
public People(String name, int age, String sex) {
this.name = name;
this.age = age;
this.sex = sex;
}
public void setId(int id) {
this.id = id;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
}

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package com.example.myroom.dao;
import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;
import androidx.room.Update;
import com.example.myroom.entity.People;
import java.util.List;
//dao database access object 接口处理数据库的方法签名
@Dao
public interface PeopleDao {
//添加传递一个参数对象
@Insert
void insertDataOne(People people);
//添加可以传递多个参数对象
@Insert
void insertDataS(People... people);
//删除
@Delete
int deleteDataS(People... people);
//修改传入对象设置 id 进行修改某一个
@Update
int updateData(People... people);
//查询根据id倒序
@Query("select * from people order by id desc")
List<People> getPeoples();
//根据id查询
@Query("select * from people where id =:numb")
People getPeople(Integer numb);
//删除表数据
@Query("delete from people")
void deleteTableData();
}

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package com.example.myroom.dao;
import androidx.room.Database;
import androidx.room.RoomDatabase;
import com.example.myroom.entity.People;
//抽象类继承 RoomDatabase 我们不用实现people中的方法
// version = 1 数据库版本，exportSchema = false不允许导出数据库的架构
@Database(entities = {People.class}, version = 1, exportSchema = false)
public abstract class PeopleDataBase extends RoomDatabase {
/**
* Java 抽象类的一些特点
* 不能被实例化：抽象类不能被实例化，因为它没有具体的实现细节。它只能被继承，并且子类必须实现抽象类中的所有抽象方法。
* 包含抽象方法：抽象类可以包含抽象方法，这些方法只有声明但没有实现。子类必须实现这些抽象方法，否则它也必须被声明为抽象类。
* 提供通用功能和行为：抽象类提供了一些通用功能和行为，这些功能和行为可以被其子类继承和重用。子类可以根据需要扩展这些功能和行为，或者重写它们以提供不同的实现。
* 用于设计高层次的抽象：抽象类可以用于表示一个高层次的抽象概念或者一个通用模板，使得代码更加模块化和可维护。通过将一些公共方法和行为提取到一个抽象类中，可以避免在多个子类中重复实现相同的功能。
* 扩展性：抽象类可以定义一些扩展的接口，子类可以选择实现这些接口来提供额外的功能。这使得抽象类具有很好的扩展性，可以根据需要添加新的功能和行为
*/
/*
public abstract PeopleDao peopleDao();
}

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package com.example.myroom;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import androidx.room.Room;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.dao.PeopleDataBase;
import com.example.myroom.entity.People;
import java.util.List;
public class MainActivity extends AppCompatActivity {
PeopleDataBase DB;
private Button btnInsert, btnDelete, btnUpdate, btnSelect, btnDeleteData;
private TextView textContent;
private EditText etName, etAge, etSex, etSelect, etDelete, etUpdate;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DB = Room.databaseBuilder(this, PeopleDataBase.class, "peopleDB")
// 默认不允许在主线程中连接数据库强制在主线程中处理
.allowMainThreadQueries()
.build();
textContent = findViewById(R.id.tvcontent);
etName = findViewById(R.id.etName);
etAge = findViewById(R.id.etAge);
etSex = findViewById(R.id.etSex);
etSelect = findViewById(R.id.etSelect);
etDelete = findViewById(R.id.etDelete);
etUpdate = findViewById(R.id.etUpdate);
btnInsert = findViewById(R.id.btnSave);
btnDelete = findViewById(R.id.btnDelete);
btnUpdate = findViewById(R.id.btnUpdate);
btnSelect = findViewById(R.id.btnselect);
btnDeleteData = findViewById(R.id.btnDeleteTB);
//查询数据
selectData(null);
//按钮事件插入数据
btnInsert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//插入数据防止空
String name = etName.getText().toString().equals("") ? "张三" : etName.getText().toString();
int age = etAge.getText().toString().equals("") ? 20 : Integer.parseInt(etAge.getText().toString());
String sex = etSex.getText().toString().equals("") ? "男" : etSex.getText().toString();
People people = new People(name, age, sex);
DB.peopleDao().insertDataS(people);
//查询数据
selectData(null);
}
});
//修改数据
btnUpdate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//修改
int id = etUpdate.getText().toString().equals("") ? 0 : Integer.parseInt(etUpdate.getText().toString());
if (id != 0) {
String name = etName.getText().toString();
int age = Integer.parseInt(etAge.getText().toString());
String sex = etSex.getText().toString();
People people = new People(name, age, sex);
people.setId(id);
DB.peopleDao().updateData(people);
//查询
selectData(null);
}
}
});
//删除
btnDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int id = etDelete.getText().toString().equals("") ? 0 : Integer.parseInt(etDelete.getText().toString());
if (id != 0) {
People people = new People();
people.setId(id);
DB.peopleDao().deleteDataS(people);
//查询
selectData(null);
}
}
});
//根据id 查数据
btnSelect.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int id = etSelect.getText().toString().equals("") ? 0 : Integer.parseInt(etSelect.getText().toString());
if (id != 0) {
selectData(id);
}
}
});
//删除全部数据
btnDeleteData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DB.peopleDao().deleteTableData();
}
});
}
/**
* 查询数据的方法
*/
public void selectData(Integer id) {
try {
StringBuilder text = new StringBuilder();
if (id == null || id == 0) {
List<People> peopleList = DB.peopleDao().getPeoples();
if (peopleList.size() != 0) {
for (int i = 0; i < peopleList.size(); i++) {
People people = peopleList.get(i);
text.append("id:")
.append(people.getId())
.append("---name:")
.append(people.getName())
.append("---age:")
.append(people.getAge())
.append("---sex:")
.append(people.getSex())
.append("\n");
}
} else {
text.append("没有可用的数据");
}
} else {
People people = DB.peopleDao().getPeople(id);
text.append("id:")
.append(people.getId())
.append("---name:")
.append(people.getName())
.append("---age:")
.append(people.getAge())
.append("---sex:")
.append(people.getSex());
}
textContent.setText(text.toString());
} catch (Exception e) {
Log.e("TAG", "----查询失败------------" + e.getMessage());
}
}
}

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<?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=".MainActivity">
<Button
android:id="@+id/btnUpdate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="修改"
app:layout_constraintBottom_toBottomOf="@+id/etUpdate"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/etUpdate"
app:layout_constraintTop_toTopOf="@+id/etUpdate"
app:layout_constraintVertical_bias="0.0" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.05" />
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="0dp"
android:text="Room简单应用："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/btnSave"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:text="保存"
app:layout_constraintBottom_toTopOf="@+id/guideline9"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.203"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline4" />
<Button
android:id="@+id/btnDelete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除"
app:layout_constraintBottom_toBottomOf="@+id/etDelete"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/etDelete"
app:layout_constraintTop_toTopOf="@+id/etDelete" />
<Button
android:id="@+id/btnselect"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查询"
app:layout_constraintBottom_toBottomOf="@+id/etSelect"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/etSelect"
app:layout_constraintTop_toTopOf="@+id/etSelect" />
<Button
android:id="@+id/btnDeleteTB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:text="删除表数据"
app:layout_constraintBottom_toTopOf="@+id/guideline9"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.873"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline4" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.13" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.29548565" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="姓名："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline3"
app:layout_constraintEnd_toStartOf="@+id/etName"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5" />
<EditText
android:id="@+id/etName"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入"
android:inputType="text"
app:layout_constraintBottom_toBottomOf="@+id/textView2"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/textView2"
app:layout_constraintTop_toTopOf="@+id/textView2" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.05352798" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.21" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline8"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.6" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline9"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.37" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="性别："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline6"
app:layout_constraintEnd_toStartOf="@+id/etSex"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5" />
<EditText
android:id="@+id/etSex"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入"
android:inputType="text"
app:layout_constraintBottom_toBottomOf="@+id/textView3"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/textView3"
app:layout_constraintTop_toTopOf="@+id/textView3" />
<EditText
android:id="@+id/etAge"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入"
android:inputType="number"
app:layout_constraintBottom_toBottomOf="@+id/textView4"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/textView4"
app:layout_constraintTop_toTopOf="@+id/textView4" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="年龄："
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/guideline4"
app:layout_constraintEnd_toStartOf="@+id/etAge"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline10"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.9" />
<EditText
android:id="@+id/etSelect"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入id"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/guideline8"
app:layout_constraintEnd_toStartOf="@+id/btnselect"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline9"
app:layout_constraintVertical_bias="0.0" />
<EditText
android:id="@+id/etDelete"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入id"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/guideline8"
app:layout_constraintEnd_toStartOf="@+id/btnDelete"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline9"
app:layout_constraintVertical_bias="0.451" />
<EditText
android:id="@+id/etUpdate"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="请输入id"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/guideline8"
app:layout_constraintEnd_toStartOf="@+id/btnUpdate"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/etSelect"
app:layout_constraintVertical_bias="1.0" />
<TextView
android:id="@+id/tvcontent"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/guideline10"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="@+id/guideline8"
tools:hint="这里显示数据" />
</androidx.constraintlayout.widget.ConstraintLayout>

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