android Room初步使用

墨蓝 2024-04-17 06:20 31阅读 0赞

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][Room _ _ Android _ _ Android Developers]

![35b3c3e49c464bb9bd04a761c818eaf6.png][]

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：

![0824d742a8794d7a8b81ae6cbe55189b.png][]

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<SignRecord> getSignRecordList();
    
        @Query("SELECT * FROM basic_sign_record WHERE sign_year_month = :sign_year_month")
        List<SignRecord> 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<SignRecord> getAll();
    
        @Query("SELECT * FROM basic_sign_record WHERE uid IN (:userIds)")
        List<SignRecord> 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。

[Room _ _ Android _ _ Android Developers]: https://developer.android.google.cn/topic/libraries/architecture/room?hl=zh_cn#groovy
[35b3c3e49c464bb9bd04a761c818eaf6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/15/c6b4c976577d42b4988a98988bc949aa.png
[0824d742a8794d7a8b81ae6cbe55189b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/15/5eaf27be2eaa412fa55396c122376b3a.png