android Room初步使用

现在比较流行google官方的JetPack（喷气背包），这是个什么东东呢？

其实就是谷歌官方的一套工具包，提供各种工具类，因此可以部分不用第三方的开源库了，

比如：Room，Room是安卓设备SqlLite的框架，以前也用过不少类似的第三方开源框架，比如：

GreenDao、Realm；

Realm不推荐使用，真难用，谁用谁知道！

GreenDao还不错！

既然Room是大势所趋，那么学一学它该如何使用吧；

Room 持久性库  |  Android 开发者  |  Android Developers

目前最高版本是2.4.3，如果用这个版本的话，compileSdk最低要求31，这里就暂时不用最高版本，以后再用；

主module中build.gradle文件，加上依赖：

implementation 'androidx.room:room-runtime:2.1.0-alpha03'
    annotationProcessor 'androidx.room:room-compiler:2.1.0-alpha03'
    implementation 'androidx.room:room-rxjava2:2.1.0-alpha03'

 数据库包结构如下：

AppDatabase.java文件（创建数据库名称、实例等）：

package com.example.testgps.database;
 
import android.content.Context;
import com.example.testgps.bean.SignRecord;
import com.example.testgps.database.dao.BasicDataDao;
import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;
 
// 与表映射的实体、数据库版本
@Database(entities = {SignRecord.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
 
    private static AppDatabase instance;
 
    public static void initial(Context context) {
        if (instance == null) {
            synchronized (AppDatabase.class) {
                if (instance == null) {
                    // 创建数据库名称和实例
                    instance = Room.databaseBuilder(context,
                            AppDatabase.class, "database-name").build();
                }
            }
        }
    }
 
    public static AppDatabase getInstance() {
        return instance;
    }
 
    public abstract BasicDataDao basicDataDao();
 
 
}

BasicDataDao.java文件（数据库表的CRUD等）：

package com.example.testgps.database.dao;
 
import com.example.testgps.bean.SignRecord;
import java.util.List;
import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.OnConflictStrategy;
import androidx.room.Query;
 
@Dao
public interface BasicDataDao {
    /**
     * 打卡记录表操作
     */
    @Query("SELECT * FROM basic_sign_record")
    List getSignRecordList();
 
    @Query("SELECT * FROM basic_sign_record WHERE sign_year_month = :sign_year_month")
    List getSignRecordList(String sign_year_month);
 
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insertSignRecord(SignRecord... item);
 
    @Query("DELETE FROM basic_sign_record")
    void deleteSignRecord();
 
    @Query("SELECT COUNT(*) FROM basic_sign_record")
    int getSignRecordCount();
 
    @Query("SELECT * FROM basic_sign_record")
    List getAll();
 
    @Query("SELECT * FROM basic_sign_record WHERE uid IN (:userIds)")
    List loadAllByIds(int[] userIds);
 
//    @Query("SELECT * FROM basic_sign_record WHERE first_name LIKE :first AND " +
//            "last_name LIKE :last LIMIT 1")
//    SignRecord findByName(String first, String last);
 
    @Insert
    void insertAll(SignRecord... signRecordList);
 
    @Insert
    void insert(SignRecord signRecord);
 
    @Delete
    void delete(SignRecord signRecord);
 
    /**
     * 其他表操作
     */
 
}
 

SignRecord.java文件（实体）:

package com.example.testgps.bean;
 
import androidx.annotation.NonNull;
import androidx.room.ColumnInfo;
import androidx.room.Entity;
import androidx.room.PrimaryKey;
 
@Entity(tableName = "basic_sign_record")
public class SignRecord {
    @PrimaryKey
    @NonNull
    @ColumnInfo(name = "sign_date")
    public long signDate;
 
    @ColumnInfo(name = "sign_year_month")
    public String signYearMonth;
 
    @ColumnInfo(name = "uid")
    public long uid;
 
    @ColumnInfo(name = "name")
    public String name;
 
    @ColumnInfo(name = "sign_in_time")
    public long signInTime;
 
    @ColumnInfo(name = "sign_out_time")
    public long signOutTime;
 
    public long getSignDate() {
        return signDate;
    }
 
    public void setSignDate(long signDate) {
        this.signDate = signDate;
    }
 
    public String getSignYearMonth() {
        return signYearMonth;
    }
 
    public void setSignYearMonth(String signYearMonth) {
        this.signYearMonth = signYearMonth;
    }
 
    public long getUid() {
        return uid;
    }
 
    public void setUid(long uid) {
        this.uid = uid;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public long getSignInTime() {
        return signInTime;
    }
 
    public void setSignInTime(long signInTime) {
        this.signInTime = signInTime;
    }
 
    public long getSignOutTime() {
        return signOutTime;
    }
 
    public void setSignOutTime(long signOutTime) {
        this.signOutTime = signOutTime;
    }
}
 

在自定义的Application.java文件中去初始化数据库：

public class MyApplication extends Application {
 
    public static MyApplication myApplication;
 
    @Override
    public void onCreate() {
        super.onCreate();
        myApplication = this;
        AppDatabase.initial(this);
    }
 
}

业务代码使用示例，其他的CRUD也是一样的操作：

new Thread(new Runnable() {
                @Override
                public void run() {
                    SignRecord signRecord = new SignRecord();
                    signRecord.setName("小张");
                    BasicDataDao dataDao = AppDatabase.getInstance().basicDataDao();
                    dataDao.insertSignRecord(signRecord);
                }
            }).start();

到这里就初步实现了Room的初步使用；

注意：数据库是I/O操作，所以必须执行在子线程中；

好了，又可以愉快玩耍了。