2022-11-4学习内容

1.Jetpack Room、Room增删改查

1.1build.gradle

plugins {
    id 'com.android.application'
}

android {
    compileSdk 33

    defaultConfig {
        applicationId "com.example.chapter06"
        minSdk 28
        targetSdk 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]//指定数据库schema导出的位置
            }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.3.0'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    implementation 'androidx.room:room-runtime:2.2.5'
    annotationProcessor 'androidx.room:room-compiler:2.2.5'
}

其中新增内容为：

defaultConfig {
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]//指定数据库schema导出的位置
            }
        }
    }

dependencies {

    implementation 'androidx.room:room-runtime:2.2.5'
    annotationProcessor 'androidx.room:room-compiler:2.2.5'
}

1.2BookInfo.java

package com.example.chapter06.entity;

import androidx.room.Entity;
import androidx.room.PrimaryKey;

@Entity
public class BookInfo {

    @PrimaryKey(autoGenerate = true)
    private int id;

    private String name;
    private String author;
    private String press;
    private Double price;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getPress() {
        return press;
    }

    public void setPress(String press) {
        this.press = press;
    }

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "BookInfo{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", press='" + press + '\'' +
                ", price=" + price +
                '}';
    }
}

1.3BookDao.java

package com.example.chapter06.dao;

import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;
import androidx.room.Update;

import com.example.chapter06.entity.BookInfo;

import java.util.List;

@Dao
public interface BookDao {

    // 可变参数
    @Insert
    void insert(BookInfo... book);

    @Delete
    void delete(BookInfo... book);

    @Query("DELETE FROM BookInfo")
    void deleteAll();

    @Update
    int update(BookInfo... book);

    // 加载所有书籍信息
    @Query("SELECT * FROM BookInfo")
    List<BookInfo> queryAll();

    @Query("SELECT * FROM BookInfo WHERE name = :name ORDER BY id DESC LIMIT 1")
    BookInfo queryByName(String name);
}

1.4BookDatabase.java

package com.example.chapter06.database;

import androidx.room.Database;
import androidx.room.RoomDatabase;

import com.example.chapter06.dao.BookDao;
import com.example.chapter06.entity.BookInfo;


// entities表示该数据库有哪些表，version表示数据库的版本号
// exportShema表示是否导出数据库信息的JSON串，建议设为false，若设为true还需指定json文件的保存路径。
@Database(entities = {BookInfo.class}, version=1, exportSchema = true)
public abstract class BookDatabase extends RoomDatabase {

    // 获取该数据库中某张表的持久化对象
    public abstract BookDao bookDao();
}

1.5MyApplication.java

package com.example.chapter06;

import android.app.Application;
import android.content.res.Configuration;
import android.util.Log;

import androidx.annotation.NonNull;
import androidx.room.Room;

import com.example.chapter06.database.BookDatabase;

import java.util.HashMap;

public class MyApplication extends Application {

    private static MyApplication myApp;
    // 声明一个公共的信息映射对象，可当做全局变量使用
    public HashMap<String, String> infoMap = new HashMap<>();

    // 声明一个书籍数据库对象
    private BookDatabase bookDatabase;

    public static MyApplication getInstance() {
        return myApp;
    }

    // 在APP启动时调用
    @Override
    public void onCreate() {
        super.onCreate();
        myApp = this;
        Log.d("ning", "MyApplication onCreate");

        // 构建书籍数据库的实例
        bookDatabase = Room.databaseBuilder(this, BookDatabase.class, "book")
                // 允许迁移数据库（发生数据库变更时，Room默认删除原数据库再创建新数据库，如此一来原来的记录会丢失，故而要改为迁移方式以便保存原有记录
                .addMigrations()
                // 允许在主线程中操作数据库（Room默认不能在主线程中操作数据库）
                .allowMainThreadQueries()
                .build();
    }

    // 在APP终止时调用
    @Override
    public void onTerminate() {
        super.onTerminate();
        Log.d("ning", "onTerminate");
    }

    // 在配置改变时调用，例如从竖屏变为横屏
    @Override
    public void onConfigurationChanged(@NonNull Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        Log.d("ning", "onConfigurationChanged");
    }

    // 获取书籍数据库的实例
    public BookDatabase getBookDB() {
        return bookDatabase;
    }
}

1.6RoomWriteActivity.java

package com.example.chapter06;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;

import com.example.chapter06.dao.BookDao;
import com.example.chapter06.entity.BookInfo;
import com.example.chapter06.util.ToastUtil;

import java.util.List;

public class RoomWriteActivity extends AppCompatActivity implements View.OnClickListener{

    private EditText et_name;
    private EditText et_author;
    private EditText et_press;
    private EditText et_price;
    private BookDao bookDao;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_room_write);

        et_name = findViewById(R.id.et_name);
        et_author = findViewById(R.id.et_author);
        et_press = findViewById(R.id.et_press);
        et_price = findViewById(R.id.et_price);

        findViewById(R.id.btn_save).setOnClickListener(this);
        findViewById(R.id.btn_delete).setOnClickListener(this);
        findViewById(R.id.btn_update).setOnClickListener(this);
        findViewById(R.id.btn_query).setOnClickListener(this);

        // 从App实例中获取唯一的书籍持久化对象
        bookDao = MyApplication.getInstance().getBookDB().bookDao();
    }

    @Override
    public void onClick(View v) {
        String name = et_name.getText().toString();
        String author = et_author.getText().toString();
        String press = et_press.getText().toString();
        String price = et_price.getText().toString();

        switch (v.getId()) {
            case R.id.btn_save:
                // 以下声明一个书籍信息对象，并填写它的各字段值
                BookInfo b1 = new BookInfo();
                b1.setName(name);
                b1.setAuthor(author);
                b1.setPress(press);
                b1.setPrice(Double.parseDouble(price));
                bookDao.insert(b1);
                ToastUtil.show(this, "保存成功");
                break;
            case R.id.btn_delete:
                BookInfo b2 = new BookInfo();
                b2.setId(1);
                bookDao.delete(b2);
                break;
            case R.id.btn_update:
                BookInfo b3 = new BookInfo();
                // 根据名字查询到数据库中已有的记录
                BookInfo b4 = bookDao.queryByName(name);
                b3.setId(b4.getId());
                b3.setName(name);
                b3.setAuthor(author);
                b3.setPress(press);
                b3.setPrice(Double.parseDouble(price));
                bookDao.update(b3);
                break;
            case R.id.btn_query:
                List<BookInfo> list = bookDao.queryAll();
                for (BookInfo b : list) {
                    Log.d("ning", b.toString());
                }
                break;
        }
    }
}

1.7activity_room_write.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_name"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text=" 书名："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_name"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginTop="3dp"
            android:layout_marginBottom="3dp"
            android:layout_weight="1"
            android:background="@drawable/editext_selector"
            android:hint="请输入书籍名称"
            android:inputType="text"
            android:textColor="@color/black"
            android:textSize="17sp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_author"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text=" 作者："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_author"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginTop="3dp"
            android:layout_marginBottom="3dp"
            android:layout_weight="1"
            android:background="@drawable/editext_selector"
            android:hint="请输入作者姓名"
            android:inputType="text"
            android:textColor="@color/black"
            android:textSize="17sp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_press"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text=" 出版社："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_press"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginTop="3dp"
            android:layout_marginBottom="3dp"
            android:layout_weight="1"
            android:background="@drawable/editext_selector"
            android:hint="请输入出版社名称"
            android:inputType="text"
            android:textColor="@color/black"
            android:textSize="17sp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_price"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text=" 价格："
            android:textColor="@color/black"
            android:textSize="17sp" />

        <EditText
            android:id="@+id/et_price"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_marginTop="3dp"
            android:layout_marginBottom="3dp"
            android:layout_weight="1"
            android:background="@drawable/editext_selector"
            android:hint="请输入书籍价格"
            android:inputType="text"
            android:textColor="@color/black"
            android:textSize="17sp" />

    </LinearLayout>

    <Button
        android:id="@+id/btn_save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="添加"
        android:textColor="@color/black"
        android:textSize="17sp" />

    <Button
        android:id="@+id/btn_delete"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="删除"
        android:textColor="@color/black"
        android:textSize="17sp" />

    <Button
        android:id="@+id/btn_update"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="修改"
        android:textColor="@color/black"
        android:textSize="17sp" />

    <Button
        android:id="@+id/btn_query"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查询"
        android:textColor="@color/black"
        android:textSize="17sp" />

</LinearLayout>

1.8效果：

1.8.1schema：

1.json

{
  "formatVersion": 1,
  "database": {
    "version": 1,
    "identityHash": "b72d0053ebd9b4bd9d877174fb85477e",
    "entities": [
      {
        "tableName": "BookInfo",
        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `name` TEXT, `author` TEXT, `press` TEXT, `price` REAL)",
        "fields": [
          {
            "fieldPath": "id",
            "columnName": "id",
            "affinity": "INTEGER",
            "notNull": true
          },
          {
            "fieldPath": "name",
            "columnName": "name",
            "affinity": "TEXT",
            "notNull": false
          },
          {
            "fieldPath": "author",
            "columnName": "author",
            "affinity": "TEXT",
            "notNull": false
          },
          {
            "fieldPath": "press",
            "columnName": "press",
            "affinity": "TEXT",
            "notNull": false
          },
          {
            "fieldPath": "price",
            "columnName": "price",
            "affinity": "REAL",
            "notNull": false
          }
        ],
        "primaryKey": {
          "columnNames": [
            "id"
          ],
          "autoGenerate": true
        },
        "indices": [],
        "foreignKeys": []
      }
    ],
    "views": [],
    "setupQueries": [
      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, 'b72d0053ebd9b4bd9d877174fb85477e')"
    ]
  }
}

1.8.2增：

点击“查询”控制台输出：

2022-11-04 21:01:52.857 5045-5045/com.example.chapter06 D/ning: BookInfo{id=1, name='bookName1', author='author1', press='press1', price=19.0}
2022-11-04 21:01:52.858 5045-5045/com.example.chapter06 D/ning: BookInfo{id=2, name='bookName1', author='author1', press='press1', price=19.0}

1.8.3删除：

根据id=1删除：点击“查询”控制台输出：

2022-11-04 21:03:06.541 5045-5045/com.example.chapter06 D/ning: BookInfo{id=2, name='bookName1', author='author1', press='press1', price=19.0}

发现id=1的已成功删除。

1.8.4修改：

按下图输入，点“修改”，

点击“查询”控制台输出：

2022-11-04 21:05:01.265 5045-5045/com.example.chapter06 D/ning: BookInfo{id=2, name='bookName1', author='author2', press='press2', price=222.0}

发现name为bookName1的对象的各字段已成功修改。

原文地址：http://www.cnblogs.com/pingfanliliang/p/16856469.html

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