android Room使用

使用Room实现数据库增删改查。

1. 引入room

def room_version = "2.3.0"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"

2. 添加配置

android {
defaultConfig {
javaCompileOptions {
annotationProcessorOptions {
arguments = [
// app内会自动生产schemas文件夹
"room.schemaLocation":"$projectDir/schemas".toString()
]
}
}
}
}

3.创建实体类

@Entity(tableName = "device") // 表名
public class DeviceEntity {
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "id")
private int id;
private String name;
private String code;
public DeviceEntity() {
}
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 getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
}

4.创建Dao文件

@Dao
public interface DeviceDao {
// 查全部
@Query("SELECT * FROM device")
List<DeviceEntity> getAll();
// 模糊查询
@Query("SELECT * FROM device WHERE name LIKE '%' || :keyword || '%' OR code LIKE '%' || :keyword || '%'")
List<DeviceEntity> getAll(String keyword);
// 查询是否存在
@Query("SELECT EXISTS (SELECT 1 FROM device WHERE code = :code OR name = :name)")
boolean isExistDevice(String code, String name);
// 插入
@Insert
void insert(DeviceEntity device);
// 修改
@Update
int updateDevice(DeviceEntity device);
// 删除
@Query("DELETE FROM device where id=:id")
void delete(int id);
}

5.创建Database

@Database(entities = {DeviceEntity.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract DeviceDao deviceDao();
private static volatile AppDatabase INSTANCE;
public static AppDatabase getDatabase(final Context context) {
if (INSTANCE == null) {
synchronized (AppDatabase.class) {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
AppDatabase.class, "my_db") // 数据库名称
.allowMainThreadQueries()
.build();
}
}
}
return INSTANCE;
}
}

6.使用

DeviceDao deviceDao = AppDatabase.getDatabase(this).deviceDao();
deviceDao.getAll();

7.版本升级
修改实体类中的字段后，修改AppDatabase文件

@Database(entities = {DeviceEntity.class}, version = 2)
public abstract class AppDatabase extends RoomDatabase {
public abstract DeviceDao deviceDao();
private static volatile AppDatabase INSTANCE;
//添加版本号1到2的处理
private static Migration MIGRATION_1_2 = new Migration(1,2) {
@Override
public void migrate(@NonNull SupportSQLiteDatabase database) {
database.execSQL("ALTER TABLE device " + " ADD COLUMN signal TEXT "); // 添加字段
}
};
public static AppDatabase getDatabase(final Context context) {
if (INSTANCE == null) {
synchronized (AppDatabase.class) {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
AppDatabase.class, "my_db") // 数据库名称
.allowMainThreadQueries()
.addMigrations(MIGRATION_1_2) // 添加
.build();
}
}
}
return INSTANCE;
}
}

最后

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