Part 7: Implementing RoomDB for the saving Bookmark in local storage

Here we have implemented RoomDB for storing news locally in app in the bookmark section

• We have to create a NewsDao

package com.example.newsapp.data.local

import androidx.lifecycle.LiveData
import androidx.room.Dao
import androidx.room.Delete
import androidx.room.Insert
import androidx.room.OnConflictStrategy
import androidx.room.Query
import com.example.newsapp.domain.model.Article
import kotlinx.coroutines.flow.Flow


@Dao
interface NewsDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun upsert(article: Article)

    @Delete
    suspend fun delete(article: Article)

    @Query("SELECT * FROM Article")
    fun getArticles(): Flow<List<Article>>

    @Query("SELECT * FROM Article WHERE url=:url")
    suspend fun getArticle(url: String): Article?


}

• First we have to convert

package com.example.newsapp.data.local

import androidx.room.ProvidedTypeConverter
import androidx.room.TypeConverter
import com.example.newsapp.domain.model.Source


@ProvidedTypeConverter
class NewsTypeConverter {


    @TypeConverter
    fun sourceToString(source: Source): String{
        return "${source.id},${source.name}"
    }

    @TypeConverter
    fun stringToSource(source: String): Source{
        return source.split(',').let { sourceArray ->
            Source(id = sourceArray[0], name = sourceArray[1])
        }
    }
}

• We have to create News Database file for the implementation of the room database

package com.example.newsapp.data.local

import androidx.room.Database
import androidx.room.RoomDatabase
import androidx.room.TypeConverters
import com.example.newsapp.domain.model.Article

@Database(entities = [Article::class],version = 1,)
@TypeConverters(NewsTypeConverter::class)
abstract class NewsDatabase : RoomDatabase() {

    abstract val newsDao: NewsDao

}

• We have to provide it in the App Module

@Provides
    @Singleton
    fun provideNewsDatabase(
        application: Application
    ): NewsDatabase {
        return Room.databaseBuilder(
            context = application,
            klass = NewsDatabase::class.java,
            name = NEW_DATABASE
        ).addTypeConverter(NewsTypeConverter())
            .fallbackToDestructiveMigration()
            .build()

    }

    @Provides
    @Singleton
    fun provideNewsDao(
        newsDatabase: NewsDatabase
    ): NewsDao {
        return newsDatabase.newsDao
    }


}

Make Sure to app the Primary key

@Parcelize
@Entity
data class Article(
    val author: String,
    val content: String,
    val description: String,
    val publishedAt: String,
    val source: Source,
    val title: String,
    @PrimaryKey val url: String,
    val urlToImage: String
): Parcelable

package com.example.newsapp.domain.model

import android.os.Parcelable
import kotlinx.parcelize.Parcelize


@Parcelize
data class Source(
    val id: String,
    val name: String
): Parcelable

This is how you can make the Detail Screen

Lets Build Bookmark Screen

• We have to make the use case for Upsert, Delete, Get Article, Get Articles

package com.example.newsapp.domain.usecases.news

import com.example.newsapp.data.local.NewsDao
import com.example.newsapp.domain.model.Article
import com.example.newsapp.domain.repository.NewsRepository

class UpsertArticle(
    private val newsRepository: NewsRepository
) {

    suspend operator fun invoke(article: Article){
        newsRepository.upsertArticle(article = article)
    }

}

package com.example.newsapp.domain.usecases.news

import com.example.newsapp.data.local.NewsDao
import com.example.newsapp.domain.model.Article
import com.example.newsapp.domain.repository.NewsRepository

class DeleteArticle (
    private val newsRepository: NewsRepository
) {

    suspend operator fun invoke(article: Article){
        newsRepository.deleteArticle(article = article)
    }

}

package com.example.newsapp.domain.usecases.news

import com.example.newsapp.data.local.NewsDao
import com.example.newsapp.domain.model.Article
import com.example.newsapp.domain.repository.NewsRepository

class SelectArticle(
    private val newsRepository: NewsRepository
) {
     suspend  operator fun invoke(url: String): Article? {
      return  newsRepository.getArticle(url)
    }
}

package com.example.newsapp.domain.usecases.news

import com.example.newsapp.data.local.NewsDao
import com.example.newsapp.domain.model.Article
import com.example.newsapp.domain.repository.NewsRepository
import kotlinx.coroutines.flow.Flow

class SelectArticles(
    private val newsRepository: NewsRepository
) {

    operator fun invoke(): Flow<List<Article>> {
        return newsRepository.getArticles()
    }

}

• Make sure to add this in the data class

data class NewsUseCases(
    val getNews: GetNews,
    val searchNews: SearchNews,
    val upsertArticle: UpsertArticle,
    val deleteArticle: DeleteArticle,
    val selectArticles: SelectArticles,
    val selectArticle: SelectArticle,
)

Provide it in a App Module

@Provides
@Singleton
fun provideNewsUseCases(
    newsRepository: NewsRepository,
): NewsUseCases {
    return NewsUseCases(
        getNews = GetNews(newsRepository),
        searchNews = SearchNews(newsRepository),
        upsertArticle = UpsertArticle(newsRepository),
        deleteArticle = DeleteArticle(newsRepository),
        selectArticles = SelectArticles(newsRepository),
        selectArticle = SelectArticle(newsRepository),
    )
}

• Create a Bookmark State

package com.example.newsapp.presentation.bookmark

import com.example.newsapp.domain.model.Article

data class BookmarkState(
    val articles: List<Article> = emptyList(),

)

• After that we have to create a viewmodel for bookmark

package com.example.newsapp.presentation.bookmark

import androidx.compose.runtime.State
import androidx.compose.runtime.mutableStateOf
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.example.newsapp.domain.usecases.news.NewsUseCases
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.flow.launchIn
import kotlinx.coroutines.flow.onEach
import javax.inject.Inject

@HiltViewModel
class BookmarkViewModel @Inject constructor(
    private val newsUseCases: NewsUseCases
) : ViewModel()
{

    private val _state = mutableStateOf(BookmarkState())
    val state: State<BookmarkState> = _state

    init {
        getArticles()
    }

    private fun getArticles() {
        newsUseCases.selectArticles().onEach {
            _state.value = _state.value.copy(articles = it.reversed())
        }.launchIn(viewModelScope)
    }
}

• We have to create new function as

@Composable
fun ArticlesList(
    modifier: Modifier = Modifier,
    articles: List<Article>,
    onClick: (Article) -> Unit
) 

package com.example.newsapp.presentation.common

import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.paging.LoadState
import androidx.paging.compose.LazyPagingItems
import com.example.newsapp.domain.model.Article
import com.example.newsapp.presentation.Dimens.ExtraSmallPadding2
import com.example.newsapp.presentation.Dimens.MediumPadding1
import com.example.newsapp.presentation.Dimens.MediumPadding2


@Composable
fun ArticlesList(
    modifier: Modifier = Modifier,
    articles: List<Article>,
    onClick: (Article) -> Unit
) {
    if (articles.isEmpty()){
        EmptyScreen()
    }
    LazyColumn(
        modifier = modifier.fillMaxSize(),
        verticalArrangement = Arrangement.spacedBy(MediumPadding1),
        contentPadding = PaddingValues(all = ExtraSmallPadding2)
    ) {
        items(
            count = articles.size,
        ) {
            articles[it].let { article ->
                ArticleCard(article = article, onClick = { onClick(article) })
            }
        }
    }

}



@Composable
fun ArticlesList(
    modifier: Modifier = Modifier,
    articles: LazyPagingItems<Article>,
    onClick: (Article) -> Unit
) {

    val handlePagingResult = handlePagingResult(articles = articles)


    if (handlePagingResult) {
        LazyColumn(
            modifier = modifier.fillMaxSize(),
            verticalArrangement = Arrangement.spacedBy(MediumPadding1),
            contentPadding = PaddingValues(all = ExtraSmallPadding2)
        ) {
            items(
                count = articles.itemCount,
            ) {
                articles[it]?.let { article ->
                    ArticleCard(article = article, onClick = { onClick(article) })
                }
            }
        }
    }
}

@Composable
fun handlePagingResult(
    modifier: Modifier = Modifier,
    articles: LazyPagingItems<Article>
): Boolean {

    val loadState = articles.loadState
    val error = when {
        loadState.refresh is LoadState.Error -> loadState.refresh as LoadState.Error
        loadState.prepend is LoadState.Error -> loadState.prepend as LoadState.Error
        loadState.append is LoadState.Error -> loadState.append as LoadState.Error
        else -> null
    }

    return when {
        loadState.refresh is LoadState.Loading -> {
            ShimmerEffect()
            false
        }

        else -> {
            true
        }
    }


}

@Composable
private fun ShimmerEffect(modifier: Modifier = Modifier) {
    Column(verticalArrangement = Arrangement.spacedBy(MediumPadding2)) {
        repeat(10) {
            ArticleCardShimmerEffect(
                modifier = Modifier.padding(horizontal = MediumPadding2)
            )
        }
    }
}

• Hence we have successfully implemented the detail screen.

If you have not read Part 6 of the series the here is the link below
https://medium.com/@mohitrdamke/part-6-implementing-news-detail-screen-in-app-c522856aa74b

You can visit the introduction article for the news app with the link below
https://medium.com/@mohitrdamke/news-app-clean-code-architecture-paging-room-db-in-android-studio-24919ba7d16a


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