Android : Room 数据库的基本用法 _简单应用_二_优化
2023-12-14 18:22:54
1.导入依赖 build.gradle
dependencies {
//Room
def room_version = "2.5.0"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"
// 使用androidx版本库 ViewModelProviders
implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0-alpha03'
}
2.PeopleDAtaBase.java 修改 为单例:
package com.example.myroom.dao;
import android.content.Context;
import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;
import com.example.myroom.entity.People;
/** 优化 改成单例模式 singleton
抽象类 继承 RoomDatabase 我们不用实现people中的方法
version = 1 版本号,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 {
private static PeopleDataBase peopleDataBase;
public static synchronized PeopleDataBase getPeopleDataBase(Context context){
if(peopleDataBase == null){
peopleDataBase = Room.databaseBuilder(context.getApplicationContext(),PeopleDataBase.class,"peopleDB")
// 默认不允许在主线程中连接数据库 在主线程中处理 使用了异步任务AsyncTask
// .allowMainThreadQueries()
.build();
}
return peopleDataBase;
}
/**
* 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();
}
3.添加异步任务 AsyncTask
3.1保存数据方法:InsertAsyncTask .java
package com.example.myroom.task;
import android.os.AsyncTask;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.entity.People;
/** AsyncTask 在 API 级别 30 中此字段已弃用 , 请改用标准或 Kotlin 并发实用程序
* 插入数据 异步任务
* android.os.AsyncTask<Params、进度、结果>
* */
public class InsertAsyncTask extends AsyncTask<People,Void,Void> {
/**
* 4个步骤
* 执行异步任务时,任务会经历 4 个步骤:
*
* onPreExecute(),在任务之前的 UI 线程上调用 被执行。此步骤通常用于设置任务,例如 在用户界面中显示进度条。
*
* doInBackground(Params),在后台线程上调用 执行完毕后立即执行。
* 此步骤用于 执行可能需要很长时间的后台计算。参数 的异步任务被传递到此步骤。
* 计算结果必须 由此步骤返回,并将传递回最后一步。这一步 还可用于发布一个或多个单元 的进步。
* 这些值在步骤中发布在 UI 线程上。onPreExecute()publishProgress(Progress)onProgressUpdate(Progress)
*
* onProgressUpdate(Progress),在 UI 线程上调用 调用 。
* 执行的时间是 定义。此方法用于在用户中显示任何形式的进度 接口,而后台计算仍在执行。
* 例如 它可用于对进度条进行动画处理或在文本字段中显示日志。publishProgress(Progress)
*
* onPostExecute(Result),在后台之后的 UI 线程上调用 计算完成。将后台计算的结果传递给主界面。
* */
private PeopleDao peopleDao;
public InsertAsyncTask(PeopleDao peopleDao){
this.peopleDao=peopleDao;
}
@Override
protected Void doInBackground(People... people) {
//在后台执行 插入数据操作
peopleDao.insertDataS(people);
return null;
}
}
3.2删除数据方法:DeleteAsyncTask?.java
package com.example.myroom.task;
import android.os.AsyncTask;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.entity.People;
public class DeleteAsyncTask extends AsyncTask<People,Void,Void> {
private PeopleDao peopleDao;
public DeleteAsyncTask(PeopleDao peopleDao){
this.peopleDao = peopleDao;
}
@Override
protected Void doInBackground(People... people) {
peopleDao.deleteDataS(people);
return null;
}
}
3.3 删除表数据方法?DeleteTBAsyncTask .java
package com.example.myroom.task;
import android.os.AsyncTask;
import com.example.myroom.dao.PeopleDao;
public class DeleteTBAsyncTask extends AsyncTask<Void,Void,Void> {
private PeopleDao peopleDao;
public DeleteTBAsyncTask(PeopleDao peopleDao) {
this.peopleDao = peopleDao;
}
@Override
protected Void doInBackground(Void... voids) {
peopleDao.deleteTableData();
return null;
}
}
3.4 根据id查询数据方法?SelectByIdAsyncTask .java
package com.example.myroom.task;
import android.os.AsyncTask;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.entity.People;
public class SelectByIdAsyncTask extends AsyncTask<Integer,Void,People> {
private PeopleDao peopleDao;
public SelectByIdAsyncTask(PeopleDao peopleDao) {
this.peopleDao = peopleDao;
}
@Override
protected People doInBackground(Integer... integers) {
People people =peopleDao.getPeople(integers[0]);
return people;
}
}
3.5 更新数据方法?UpdateAsyncTask .java
package com.example.myroom.task;
import android.os.AsyncTask;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.entity.People;
public class UpdateAsyncTask extends AsyncTask<People,Void,Void> {
private PeopleDao peopleDao;
public UpdateAsyncTask( PeopleDao peopleDao){
this.peopleDao = peopleDao;
}
@Override
protected Void doInBackground(People... people) {
peopleDao.updateData(people);
return null;
}
}
4.修改PeopleDao.java
@Dao
public interface PeopleDao {
...
//查询 根据id倒序
@Query("select * from people order by id desc")
LiveData<List<People>> getPeopleLive(); //设置成为可以观察的数据 LiveDAta
// List<People> getPeoples();
...
}
5.创建仓库 PeopleRepository.java
package com.example.myroom.dao;
import android.content.Context;
import android.util.Log;
import androidx.lifecycle.LiveData;
import com.example.myroom.entity.People;
import com.example.myroom.task.DeleteAsyncTask;
import com.example.myroom.task.DeleteTBAsyncTask;
import com.example.myroom.task.InsertAsyncTask;
import com.example.myroom.task.SelectByIdAsyncTask;
import com.example.myroom.task.UpdateAsyncTask;
import java.util.List;
public class PeopleRepository {
PeopleDao peopleDao;
LiveData<List<People>> allPeopleLive;
public PeopleRepository(Context context) {
PeopleDataBase peopleDataBase = PeopleDataBase.getPeopleDataBase(context.getApplicationContext());
peopleDao = peopleDataBase.peopleDao();
allPeopleLive = peopleDao.getPeopleLive();
}
public LiveData<List<People>> getAllPeopleLive() {
return allPeopleLive;
}
public void insertPeoples(People... people) {
new InsertAsyncTask(peopleDao).execute(people);
}
public void updatePeoples(People... people) {
new UpdateAsyncTask(peopleDao).execute(people);
}
public void deletePeople(People... people) {
new DeleteAsyncTask(peopleDao).execute(people);
}
public void deleteTBPeoples() {
new DeleteTBAsyncTask(peopleDao).execute();
}
public People selectPeopleById(Integer id) {
People people = null;
try {
people = new SelectByIdAsyncTask(peopleDao).execute(id).get();
} catch (Exception e) {
Log.e("TAG", "根据id查询失败" + e.getMessage());
}
return people;
}
}
6.创建MyViewModel .java??
package com.example.myroom;
import android.app.Application;
import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.LiveData;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.dao.PeopleRepository;
import com.example.myroom.entity.People;
import java.util.List;
//管理界面数据
public class MyViewModel extends AndroidViewModel {
private PeopleDao peopleDao;
private PeopleRepository peopleRepository;
public MyViewModel(@NonNull Application application) {
super(application);
peopleRepository = new PeopleRepository(application);
}
public LiveData<List<People>> getAllPeopleLive() {
return peopleRepository.getAllPeopleLive();
}
public void insertPeoples(People... people){
peopleRepository.insertPeoples(people);
}
public void updatePeoples(People... people){
peopleRepository.updatePeoples(people);
}
public void deletePeople(People... people){
peopleRepository.deletePeople(people);
// new DeleteAsyncTask(peopleDao).execute(people);
}
public void deleteTBPeoples(){
peopleRepository.deleteTBPeoples();
}
public People selectPeopleById(Integer id){
return peopleRepository.selectPeopleById(id);
}
}
7.MainActivity.java
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.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;
import com.example.myroom.dao.PeopleDao;
import com.example.myroom.dao.PeopleDataBase;
import com.example.myroom.entity.People;
import com.example.myroom.task.DeleteTBAsyncTask;
import java.util.List;
public class MainActivity extends AppCompatActivity {
PeopleDataBase DB;
PeopleDao peopleDao;
MyViewModel myViewModel;
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);
// binding = DataBindingUtil.setContentView(this,R.layout.activity_main);
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);
myViewModel = ViewModelProviders.of(this).get(MyViewModel.class);
DB = PeopleDataBase.getPeopleDataBase(this);
peopleDao = DB.peopleDao();
//观察数据
myViewModel.getAllPeopleLive().observe(this, new Observer<List<People>>() {
@Override
public void onChanged(List<People> peoples) {
//内容发生改变执行执行下面代码
StringBuilder text = new StringBuilder();
for (int i = 0; i < peoples.size(); i++) {
People people = peoples.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");
}
textContent.setText(text.toString());
}
});
// //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);
myViewModel.insertPeoples(people);
// new InsertAsyncTask(peopleDao).execute(people);
// 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);
myViewModel.updatePeoples(people);
// new UpdateAsyncTask(peopleDao).execute(people);
// 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);
myViewModel.deletePeople(people);
// new DeleteAsyncTask(peopleDao).execute(people);
// 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) {
selectDataById(id);
}
}
});
//删除全部数据
btnDeleteData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// DB.peopleDao().deleteTableData();
new DeleteTBAsyncTask(peopleDao).execute();
}
});
}
/**
* 查询数据的方法
*/
public void selectDataById(Integer id) {
try {
StringBuilder text = new StringBuilder();
// People people = DB.peopleDao().getPeople(id);
// People people = new SelectByIdAsyncTask(peopleDao).execute(id).get();
People people = myViewModel.selectPeopleById(id);
text.append("id:")
.append(people.getId())
.append("---name:")
.append(people.getName())
.append("---age:")
.append(people.getAge())
.append("---sex:");
textContent.setText(text.toString());
} catch (Exception e) {
Log.e("TAG", "----查询失败------------" + e.getMessage());
}
}
}
文章来源:https://blog.csdn.net/jiayou2020527/article/details/134926749
本文来自互联网用户投稿,该文观点仅代表作者本人,不代表本站立场。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。 如若内容造成侵权/违法违规/事实不符,请联系我的编程经验分享网邮箱:veading@qq.com进行投诉反馈,一经查实,立即删除!
本文来自互联网用户投稿,该文观点仅代表作者本人,不代表本站立场。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。 如若内容造成侵权/违法违规/事实不符,请联系我的编程经验分享网邮箱:veading@qq.com进行投诉反馈,一经查实,立即删除!