Question 171082 in Android Studio Question posted in
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How do I set data fetched from an API in a new Android Studio activity?

I have a News app where I have used Retrofit to get data from API. I have shown news with cardView and Recycler view. Now I want to implement the the next step where I want if a user click on a card the whole news should display on a new activity. But to implement this I don’t have the proper idea that how to do this. Here I am providing my MainActivity , the adapter class and the interface for retrofit. I am looking for the help to implement the next step.

MainActivity.kt

class MainActivity : AppCompatActivity() {
    lateinit var adapter: NewsAdapter
   
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        getNews()
    }

    private fun getNews() {
        val news :Call<News> = NewsSeversis.newsIntence.getHeadlines("in",1)
        
        news.enqueue(object :Callback<News>{
            override fun onResponse(call: Call<News>, response: Response<News>) {
                //here response is a News response
                val news:News?=response.body()
                if (news!=null){
                    Log.d("response",news.toString())
                    adapter= NewsAdapter(news.articles)
                    newsList.adapter=adapter
                    newsList.layoutManager=LinearLayoutManager(this@MainActivity) 
                }
            }
            override fun onFailure(call: Call<News>, t: Throwable) {
                Log.d("response","error occur",t)
            }
        })
    } 
}

Adapter class for recycler view

class NewsAdapter (val artical: List<Artical>):RecyclerView.Adapter<NewsAdapter.articalViewHolder>(){
   inner class articalViewHolder(itemView: View):RecyclerView.ViewHolder(itemView)

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): articalViewHolder {
        val view:View=LayoutInflater.from(parent.context).inflate(R.layout.item_layout,parent,false)
        return articalViewHolder(view)
    }

    override fun onBindViewHolder(holder: articalViewHolder, position: Int) {
        val articals:Artical=artical[position]
        holder.itemView.apply {
            newsTitle.text=articals.title
            newsDescription.text=articals.description
            Glide.with(context).load(articals.urlToImage).into(newsImage)

        }
    }

    override fun getItemCount(): Int {
       return artical.size
    }
}

interface class

const val BASE_URL="https://newsapi.org/"
const val API_KEY="b461fea21cc242458825d1be951ebe1c"
 interface NewsInterface{
    
  @GET("v2/top-headlines?apiKey=$API_KEY")//@GET is to tell the it is a get request
    
  fun getHeadlines(@Query("country")country:String, @Query("page") page:Int) : Call<News> 
  
 }
object NewsSeversis {
   
    val newsIntence:NewsInterface
    init {
        val retrofit=Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build()
       
        newsIntence=retrofit.create(NewsInterface::class.java)
    }

}

layout for every card view

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    app:cardUseCompatPadding="true"
    app:cardCornerRadius="8dp"
    app:cardElevation="4dp">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#F1F1F1"
        android:padding="16dp">

        <ImageView
            android:id="@+id/newsImage"
            android:layout_width="match_parent"
            android:layout_height="180dp"
            android:scaleType="centerCrop"
            android:src="@drawable/ic_launcher_background"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/newsTitle"
            style="@style/TextAppearance.AppCompat.Headline"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:maxLines="2"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginTop="8dp"
            android:text="Title"
            app:layout_constraintTop_toBottomOf="@+id/newsImage" />

        <TextView
            android:id="@+id/newsDescription"
            style="@style/TextAppearance.AppCompat.Body1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:maxLines="2"
            android:text="Description"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toBottomOf="@+id/newsTitle" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>

main activity layout

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/newsList"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

Along with those I have a Artical and a News class with constructor and a Whole new activity for display the whole news on that activity

News class

ata class News(
    val totalResults:Int,
    val articles:List<Artical>
    )

Artical class

data class Artical(
    val author:String,
    val title:String,
    val description:String,
    val url:String,
    val urlToImage:String)
Tags:

2

Answers


  1. 0

    Following are the steps to get callback to activity of an item click from adapter.

    In your NewsAdapter class use a HigherOrder Function to get call back of item click.

    1. First Update the NewsAdapter

    class NewsAdapter (
val artical: List<Artical>,
private val onItemClicked: () -> Unit
                ):RecyclerView.Adapter<NewsAdapter.articalViewHolder>(){
                    // your existing code 
             override fun onBindViewHolder(holder: articalViewHolder, position: Int) {
                    val articals:Artical=artical[position]
                    holder.itemView.apply {
                        newsTitle.text=articals.title
                        newsDescription.text=articals.description
                        Glide.with(context).load(articals.urlToImage).into(newsImage)
    // ADD THIS LINE 
        setOnClickListener { onItemClicked.invoke() } 
            
                    }
                }

    2. Now update the code in MainActivity where you are creating object of NewsAdapter.

    // EXISTING CODE
adapter= NewsAdapter(news.articles){
    // CODE TO LAUNCH THE NEW ACTIVITY       
    }
// EXISTING CODE

    Feel free to ask if you have any queries.

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  2. 0

    To Identify which item was clicked we need to have an interface from which can get us the callback from Adapter to Activity, so create a interface class in Adapter. (In your case you can create it in last second line of NewsAdapter)

    interface AdapterCallback {
    fun onClick(artical: Artical?)
}

    Then we need to take an oject of this interface in Adapter’s Constructor

    class NewsAdapter (val artical: List<Artical>, callback: AdapterCallback): ...

    Then we have to use callback object on click of view(s). (In your case do the following in adapter class’s onBindViewHolder)

    holder.itemView.setOnClickListener {
    callback.onClick(articals)
}

    Now we need to listen this callback in our Activity, so we need create object in Activity in the following way

    private val adapterCallback: AdapterCallback =
        object : AdapterCallback {
            override fun onClick(artical: Artical?) {
                // Code here to navigate to desired Activity by passing required data in the intent (Example below)
                val intent = Intent(this, DestinationActivity::class.java)
                intent.putExtra("news_artical", artical)
                startActivity(intent)
            }
    }

    Now as we have object of AdapterCallback in our Activity, we need to pass it to Adapter

    adapter = NewsAdapter(news.articles, adapterCallback)

    Note: You need to make Artical Class Parcelable

    @Parcelize
data class Artical(
    val author: String,
    val title: String,
    val description: String,
    val url: String,
    val urlToImage: String
): Parcelable
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