Room数据库框架的使用

一、引入依赖

//Room数据库框架
implementation "androidx.room:room-runtime:2.4.0"
annotationProcessor "androidx.room:room-compiler:2.4.0"

二、数据库的初始化

1、从studio的asset目录中，读取并复制到内存缓存中，

try { ProjectListDataBase projectListDB = Room.databaseBuilder(mActivity.getApplicationContext(), ProjectListDataBase.class, GlobalConstant.BRIDGE_DETECT_DB_NAME) .setJournalMode(RoomDatabase.JournalMode.TRUNCATE) .createFromAsset(GlobalConstant.BRIDGE_DETECT_DB_NAME) .addMigrations(UpdateDB.BRIDGE_DETECT_MIGRATION_1_2) .allowMainThreadQueries() .build(); } catch (Exception e) { LogUtils.log(e.toString()); }

2、可以从指定路径中读取数据库

String dbPath = FileUtils.getFileBasePath() + File.separator + uid + File.separator + File.separator + GlobalConstant.PROJECT_DB_NAME; File file = new File(dbPath); if (file.exists()) { projectDB = Room.databaseBuilder(getApplicationContext(), ProjectDataBase.class, dbPath) .setJournalMode(RoomDatabase.JournalMode.TRUNCATE) .addMigrations(UpdateDB.PROJECT_MIGRATION_1_2) // .fallbackToDestructiveMigration() .allowMainThreadQueries() .build(); } else { LogUtils.log("initProjectDB: 数据库不存在------"); }

三、定义数据实体

@Parcelize @Entity(tableName = "project_member_check_result") public class ResultListBean { @PrimaryKey @NonNull @ColumnInfo(name = "project_task_id") public Integer taskId; @NonNull @ColumnInfo(name = "check_user_id") public Integer checkUserId; @NonNull @ColumnInfo(name = "check_time") public String checkTime; @Ignore public int totalCount; @Ignore public int detectCount; //非表中字段 }

四、定义数据访问对象（DAO）

@Dao public interface ResultListDao { @Insert(onConflict = REPLACE) long insert(ResultListBean bean); @Query("SELECT * FROM project_member_check_result WHERE project_task_id= :taskId and create_user_id =:uid") ResultListBean getResultByTaskId(int taskId, int uid); @Query("delete from project_member_check_result where project_task_id= :taskId and create_user_id =:uid") int deleteByTaskId(int taskId, int uid); }

五、‌创建数据库类（Database）

@Database(entities = {ProjectListBean.class, ResultListBean.class},version = BRIDGE_DETECT_ROOM_VERSION,exportSchema = false) public abstract class ProjectListDataBase extends RoomDatabase { public abstract ProjectListDao getProjectListDao(); public abstract ResultListDao getResultListDao(); }

六、数据库的使用

DiseaseDao diseaseDao = projectDB.getDiseaseDao(); List<DiseaseBean> diseaseBeans = diseaseDao.getDiseaseListByLevel(bean.diseaseLevel, bean.typeUuid);

七、数据库的升级

在RoomDatabase中，初始化时，指定version。在第二步，数据库初始化的时候，提到方法 .addMigrations(UpdateDB.BRIDGE_DETECT_MIGRATION_1_2)，，这是用来数据库升级的方法，代码中是从数据库版本1，升级到版本2

public static Migration BRIDGE_DETECT_MIGRATION_1_2 = new Migration(1, 2) { @Override public void migrate(@NonNull SupportSQLiteDatabase database) { try { database.execSQL("CREATE TABLE IF NOT EXISTS 'tunnel_list' (" + "'id' TEXT PRIMARY KEY NOT NULL, " + "'company_id' INTEGER NOT NULL, " + "'longitude' TEXT, " + "'flag' INTEGER, " + "'tunnel_id' INTEGER NOT NULL, " + "'check_time' TEXT, " + "'deck_pavement' INTEGER )"); } catch (Exception e) { LogUtils.log("BRIDGE_DETECT_MIGRATION_1_2、、、、、、"); } } };