Skip to content
Related Articles

Related Articles

Improve Article

Custom SimpleAdapter in Android with Example

  • Last Updated : 02 Dec, 2020

The Adapter acts as a bridge between the UI Component and the Data Source. It converts data from the data sources into view items that can be displayed into the UI Component. In Android, SimpleAdapter is an easy adapter to map static data to views defined in an XML (layout) file.  You can specify the data backing the list as an ArrayList of Maps. Each entry in the ArrayList corresponds to one row in the list. The Maps contain the data for each row.

Why use CustomSimpleAdapter? 

SimpleAdapter allows us to add events to each list item but what if we want to add different events to different views that are part of our list item, we cannot achieve it by using SimpleAdapter itself. In a typical android application, a list item can consist of a complex layout that may contain different views. In that condition, we have to use customize SimpleAdapter. The basic syntax of SimpleAdapter.

Syntax:

public SimpleAdapter(Context context, List<? extends Map<String, ?>> data, int resource, String[] from, int[] to)

Parameters:



context: The context where the View associated with this SimpleAdapter is running

data: A List of Maps. Each entry in the List corresponds to one row in the list. The Maps contain the data for each row, and should include all the entries specified in “from”

resource: Resource identifier of a view layout that defines the views for this list item. The layout file should include at least those named views defined in “to”

from: A list of column names that will be added to the Map associated with each item.

to: The views that should display column in the “from” parameter. These should all be TextViews. The first N views in this list are given the values of the first N columns in the from parameter.

Two most important methods of SimpleAdapter:

  1. getCount(): How many items are in the data set represented by this Adapter.
  2. getView(): Get a view that displays the data at the specified position in the data set. You can either create a View manually or inflate it from an XML layout file. When the View is inflated, the parent View (GridView, ListView…) will apply default layout parameters unless you use LayoutInflater.inflate(int, android.view.ViewGroup, boolean) to specify a root view and to prevent attachment to the root.

Example

Below is the gif of the final application that we are going to create for this article. In this, you will notice that by clicking list_item nothing happens but when we click on Image then only Toast is displayed.

Custom SimpleAdapter in Android



Step by step implementation

Step 1: Create a new Project

To create a new Project in Android Studio please refer to How to Create/Start a New Project in Android Studio using Kotlin. We are going to use Kotlin.

Step 2: Working with the activity_main.xml

Now open activity_main.xml and insert the below code in it. It will create a ConstraintLayout which consists of a ListView. Below is the code for the activity_main.xml file.

XML




<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
  
    <!-- This is the listView which will 
         display our list_items -->
    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
      
</androidx.constraintlayout.widget.ConstraintLayout>

Step 3: Creating a new layout XML file for ListItem.

Go to the app > res > layout > right-click > New > Layout Resource File and creates a XML file. Name the file as list_item. Below is the code for the list_item.xml file.

XML




<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/mainLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="2dp">
  
    <!-- ImageView which is display 
         to the left of list_item -->
    <ImageView
        android:id="@+id/avatarImageView"
        android:layout_width="65dp"
        android:layout_height="65dp"
        android:clickable="true"
        android:focusable="true"
        tools:srcCompat="@tools:sample/avatars" />
  
    <!-- LinearLayout to hold title and subtite -->
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_marginStart="4dp"
        android:orientation="vertical">
  
        <!-- TextView to display title -->
        <TextView
            android:id="@+id/titleTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="@color/black"
            android:textSize="18sp"
            android:textStyle="bold"
            tools:text="Title" />
  
        <!-- TextView to display subtitle -->
        <TextView
            android:id="@+id/subtitleTextView"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:ellipsize="end"
            android:gravity="center_vertical"
            android:maxLines="2"
            tools:text="Subtitle" />
          
    </LinearLayout>
</LinearLayout>

Step 4: Implementing CustomSimpleAdapter

Now create a new Kotlin class file and name it CustomSimpleAdapter. In this file, we will override the getView() method to add the custom code. Below is the code for the CustomSimpleAdapter.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin




import android.content.Context
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.SimpleAdapter
import android.widget.TextView
import android.widget.Toast
import androidx.annotation.IdRes
import androidx.annotation.LayoutRes
  
class CustomSimpleAdapter(
    private val mContext: Context,
    data: MutableList<HashMap<String, String>>,
    @LayoutRes
    res: Int,
    from: Array<String>,
    @IdRes
    to: IntArray
) :
    // Passing these params to SimpleAdapter
    SimpleAdapter(mContext, data, res, from, to) {
  
    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
          
        // Get the view in our case list_item.xml
        val view = super.getView(position, convertView, parent)
  
        // Getting reference of ImageView that we 
        // have used in our list_item.xml file
        // so that we can add user defined code
        val avatarImageView = view.findViewById<ImageView>(R.id.avatarImageView)
  
        // Reference of TextView which is treated a title
        val titleTextView = view.findViewById<TextView>(R.id.titleTextView)
  
        // Adding an clickEvent to the ImageView, as soon as we click this
        // ImageView we will see a Toast which will display a message
        // Note: this event wil only fire when ImageView is pressed and
        //       not when whole list_item is pressed
        avatarImageView.setOnClickListener {
            Toast.makeText(
                mContext,
                "Image with title ${titleTextView.text} is pressed",
                Toast.LENGTH_SHORT
            ).show()
        }
  
        // Finally returning our view
        return view
    }
}

Step 5: Working with the MainActivity.kt file

Before writing any code in MainActivity.kt file please add images that you want to show. Below is the code for MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Java




import android.os.Bundle
import android.widget.ListView
import androidx.appcompat.app.AppCompatActivity
  
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Because SimpleAdapter works with static 
        // data so we need to initialize static data
  
        // This is the array for TitleText
        val titles = arrayOf("Test1", "Test2", "Test3")
  
        // This array is for SubtitleText
        val subtitles= arrayOf("This is test1 subtitle", "This is test2 subtitle", "This is test3 subtitle")
  
        // These are the Id's of the images that will be displayed as avatar
        val images = arrayOf(R.drawable.test1, R.drawable.test2, R.drawable.test3)
  
        // Instantiating our data List, which is a list of HashMap
        val data: MutableList<HashMap<String, String>> = mutableListOf()
  
        // Populating our data List with the 
        // arrays that we have already defined
        for (i in titles.indices) {
            val cur: HashMap<String, String> = HashMap()
            cur["titleText"] = titles[i]
            cur["subtitleText"] = subtitles[i]
            cur["avatarImage"] = "${images[i]}"
            data.add(cur)
        }
  
        // From and To array which will be used to map, HashMap values
        // to the Views that are defined in the XML file (in our case list_item.xml)
        val from = arrayOf("avatarImage", "titleText", "subtitleText")
        val to = intArrayOf(R.id.avatarImageView, R.id.titleTextView, R.id.subtitleTextView)
  
        // Instantiating customSimpleAdapter with the above values
        val customSimpleAdapter = CustomSimpleAdapter(this, data, R.layout.list_item, from, to)
  
        // Getting reference of listView which is defined in activity_main.xml
        val listView = findViewById<ListView>(R.id.listView)
  
        // Finally, setting adapter to our customSimpleAdapter
        listView.adapter = customSimpleAdapter
    }
}

Output:

Want a more fast-paced & competitive environment to learn the fundamentals of Android?
Click here to head to a guide uniquely curated by our experts with the aim to make you industry ready in no time!



My Personal Notes arrow_drop_up
Recommended Articles
Page :