1.1Androidx 地址

versions.room = "2.2.5"
deps.room = "androidx.room:room-runtime:$versions.room"
deps.roomcompiler = "androidx.room:room-compiler:$versions.room"

1.2建表

@Entity(tableName = "user_info")
public class Im_user {
//主键
    @PrimaryKey
    @NonNull
    public String user_id;
    @ColumnInfo
    public String user_name;
    @ColumnInfo
    public String user_photo;
    @ColumnInfo
    public String user_sex;


    public Im_user(@NonNull String user_id, String user_name, String user_photo) {
        this.user_id = user_id;
        this.user_name = user_name;
        this.user_photo = user_photo;
    }

1.3dao 操作

@Dao
public interface ImUserDao {

    @Query("SELECT * FROM user_info")
    List<Im_user> getAll();

    @Query("SELECT * FROM user_info WHERE user_id = :user_id")
    Im_user queryUserByid(String user_id);

    @Insert(onConflict = REPLACE)
    void insertAll(Im_user... users);

    @Delete
    void delete(Im_user user);
}

1.4数据配置

@Database(entities = {Im_user.class}, version = 6)
public abstract class DatabaseConfig extends RoomDatabase {
    public abstract ImUserDao userDao();
}

1.5

public class DatabaseInitialize {

    private static DatabaseConfig databaseConfig;

    private DatabaseInitialize() {
    }

    private static Migration MIGRATION_1_2 = new Migration(1, 2) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("ALTER TABLE user_info "
                    + " ADD COLUMN user_photo TEXT");
        }
    };
    private static Migration MIGRATION_2_3 = new Migration(2, 3) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("ALTER TABLE user_info "
                    + " ADD COLUMN user_sex INTEGER NOT NULL DEFAULT 0 ");
        }
    };
    private static Migration MIGRATION_3_4 = new Migration(3, 4) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            // 创建临时表
            database.execSQL(
                    "CREATE TABLE  IF NOT EXISTS users_new (user_id TEXT NOT NULL, user_name TEXT, user_photo TEXT,user_sex TEXT, PRIMARY KEY(user_id))");

            // 拷贝数据
            database.execSQL(
                    "INSERT INTO users_new (user_id, user_name, user_photo,user_sex) SELECT user_id, user_name, user_photo,user_sex FROM user_info");
            // 删除老的表
//            database.execSQL("DROP TABLE user_info");
//            // 改名
//            database.execSQL("ALTER TABLE users_new RENAME TO user_info");
            //删除列
//            ALTER TABLE table_name
//            DROP COLUMN column_name
            //这种做法是不支持的
//            database.execSQL("ALTER TABLE user_info" + " ALTER COLUMN  user_sex TEXT NOT NULL");
        }
    };
    private static Migration MIGRATION_4_5 = new Migration(4, 5) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            // 创建临时表
            database.execSQL(
                    "CREATE TABLE  IF NOT EXISTS users_new2 (user_id TEXT NOT NULL, user_name TEXT, user_photo TEXT,user_sex TEXT, PRIMARY KEY(user_id))");

            // 拷贝数据
            database.execSQL(
                    "INSERT INTO users_new2 (user_id, user_name, user_photo,user_sex) SELECT user_id, user_name, user_photo,user_sex FROM user_info");
            // 删除老的表
//            database.execSQL("DROP TABLE user_info");
//            // 改名
//            database.execSQL("ALTER TABLE users_new RENAME TO user_info");
            //删除列
//            ALTER TABLE table_name
//            DROP COLUMN column_name
            //这种做法是不支持的
//            database.execSQL("ALTER TABLE user_info" + " ALTER COLUMN  user_sex TEXT NOT NULL");
        }
    };
    private static Migration MIGRATION_5_6 = new Migration(5, 6) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            //将原表改成暂存表
            database.execSQL("ALTER TABLE user_info RENAME TO temp_user_info");
            // 用原表创建新表
            database.execSQL(
                    "CREATE TABLE IF NOT EXISTS user_info (user_id TEXT NOT NULL, user_name TEXT, user_photo TEXT, user_sex TEXT, PRIMARY KEY(user_id))");

            // 拷贝数据
            database.execSQL(
                    "INSERT INTO user_info SELECT * FROM temp_user_info");
            // 删除老的表
            database.execSQL("DROP TABLE temp_user_info");

            //删除列
//            ALTER TABLE table_name
//            DROP COLUMN column_name
            //这种做法是不支持的
//            database.execSQL("ALTER TABLE user_info" + " ALTER COLUMN  user_sex TEXT NOT NULL");
        }
    };
    private static Migration MIGRATION_1_3 = new Migration(1, 3) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("ALTER TABLE user_info "
                    + " ADD COLUMN user_photo TEXT");
            database.execSQL("ALTER TABLE user_info "
                    + " ADD COLUMN user_sex INTEGER NOT NULL DEFAULT 0 ");
        }
    };

    public static void init(Context context) {
        // 生成数据库实例
        synchronized (DatabaseInitialize.class) {
            if (databaseConfig == null) {
                databaseConfig = Room
                        .databaseBuilder(context.getApplicationContext(), DatabaseConfig.class, "test1.db")
                        //是否允许在主线程进行查询
                        .allowMainThreadQueries()
                        //数据库创建和打开后的回调
                        //.addCallback()
                        //设置查询的线程池
                        //.setQueryExecutor()
                        .openHelperFactory(new SafeHelperFactory("123456".toCharArray()))
                        //room的日志模式
                        //.setJournalMode()
                        //数据库升级异常之后的回滚
                        //.fallbackToDestructiveMigration()
                        //数据库升级异常后根据指定版本进行回滚
                        //.fallbackToDestructiveMigrationFrom()
                        //数据库升级的入口（如果没有配置升级的时候会将数据库内容全部清除）
                        .addMigrations(MIGRATION_1_2, MIGRATION_2_3, MIGRATION_3_4,MIGRATION_4_5,MIGRATION_5_6)
                        .build();
            }
        }
    }

    static DatabaseConfig getDatabaseConfig() {
        if (databaseConfig == null) {
            throw new NullPointerException("DatabaseInitialize.init(context) has not call, remember call this function in your Application.class");
        }
        return databaseConfig;
    }


}

1.6

public final class DatabaseSession {
    private DatabaseSession(){}
    public static DatabaseConfig get() {
        return DatabaseInitialize.getDatabaseConfig();
    }
}

1.7数据库加密

   implementation "com.commonsware.cwac:saferoom.x:1.3.0"
    implementation 'net.zetetic:android-database-sqlcipher:4.4.0@aar'

一行代码搞定

   databaseConfig = Room
                        .databaseBuilder(context.getApplicationContext(), DatabaseConfig.class, "test1")
                        //是否允许在主线程进行查询
                        .allowMainThreadQueries()
                        //数据库创建和打开后的回调
                        //.addCallback()
                        //设置查询的线程池
                        //.setQueryExecutor()
                        .openHelperFactory(new SafeHelperFactory("123456".toCharArray()))
                        //room的日志模式
                        //.setJournalMode()
                        //数据库升级异常之后的回滚
                        //.fallbackToDestructiveMigration()
                        //数据库升级异常后根据指定版本进行回滚
                        //.fallbackToDestructiveMigrationFrom()
                        //数据库升级的入口（如果没有配置升级的时候会将数据库内容全部清除）
                        .addMigrations(MIGRATION_1_2, MIGRATION_2_3, MIGRATION_3_4,MIGRATION_4_5,MIGRATION_5_6)
                        .build();