- 首先,在app的build.gradle文件中添加以下依赖项:
dependencies {
def lifecycle_version = "2.2.0"
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
implementation "androidx.paging:paging-runtime-ktx:2.1.2"
implementation "androidx.room:room-runtime:2.2.5"
kapt "androidx.room:room-compiler:2.2.5"
}
- 然后,创建一个Room数据库,其中包含要进行分页的实体类:
@Entity(tableName = "my_table")
data class MyEntity(
@PrimaryKey(autoGenerate = true) val id: Int = 0,
val name: String
)
@Database(entities = [MyEntity::class], version = 1, exportSchema = false)
abstract class MyDatabase : RoomDatabase() {
abstract fun myDao(): MyDao
companion object {
private const val DATABASE_NAME = "my_database"
private var instance: MyDatabase? = null
fun getInstance(context: Context): MyDatabase {
return instance ?: synchronized(this) {
instance ?: Room.databaseBuilder(
context.applicationContext,
MyDatabase::class.java,
DATABASE_NAME
).build().also { instance = it }
}
}
}
}
- 接下来,创建一个Dao接口,其中包含用于获取数据的分页查询:
@Dao
interface MyDao {
@Query("SELECT * FROM my_table ORDER BY id DESC")
fun getData(): DataSource.Factory
}
- 创建一个ViewModel类,它将使用MyDao类的方法将数据返回并对其进行分页:
class MyViewModel(application: Application) : AndroidViewModel(application) {
private val dao: MyDao = MyDatabase.getInstance(application).myDao()
fun getData(): LiveData> =
Pager(PagedList.Config.Builder()
.setPageSize(10)
.setInitialLoadSize