Alert Dialogs are the UI elements that pop up when the user performs some crucial actions with the application. These window-like elements may contain multiple or single items to select from the list or have the error message and some action buttons. In this article, it's been discussed how to implement the Alert Dialogs with the single item selection. Look at the following image to differentiate the alert dialogs with action buttons and single item selection. We will implement this project using both Java and Kotlin Programming Languages for Android.
Implementation Alert Dialog with SingleItemSelection
Step 1: Create a New Project in Android Studio
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio.
The code for that has been given in both Java and Kotlin Programming Language for Android.
Step 2: Working with the XML Files
Next, go to the activity_main.xml file, which represents the project's UI. Below is the code for the activity_main.xml file. Comments are added inside the code to help you understand the code in more detail.
activity_main.xml:
<?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"
android:orientation="vertical"
tools:context=".MainActivity"
tools:ignore="HardcodedText">
<Button
android:id="@+id/openAlertDialogButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:backgroundTint="@android:color/holo_green_dark"
android:text="OPEN ALERT DIALOG"
android:textSize="18sp"
app:layout_constraintBottom_toTopOf="@+id/selectedItemPreview"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_chainStyle="packed" />
<TextView
android:id="@+id/selectedItemPreview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Selected Item is: "
android:textSize="18sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/openAlertDialogButton" />
</androidx.constraintlayout.widget.ConstraintLayout>
Design UI:
Step 3: Working with the MainActivity File
Go to the MainActivity File and refer to the following code. Below is the code for the MainActivity File. Comments are added inside the code to understand the code in more detail. There is a need to understand the parts of the AlertDialog with single item selection.
Have a look at the following image:
The function used for implementing the single item selection is setSingleChoiceItems which is discussed below:
Syntax:
alertDialog.setSingleChoiceItems(listItems, checkedItem[0]) { dialog, which ->
}
Parameters:
- listItems: are the items to be displayed on the alert dialog.
- checkedItems: the boolean array maintains the selected values as true and unselected values as false.
- DialogInterface.OnMultiChoiceClickListener(): This is a callback when a change in the selection of items takes place.
Invoke the following code. Comments are added inside the code for better understanding.
package org.geeksforgeeks.demo;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
private Button bOpenAlertDialog;
private TextView tvSelectedItemPreview;
// Store the selected item index (-1 means no selection by default)
private int selectedItemIndex = -1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bOpenAlertDialog = findViewById(R.id.openAlertDialogButton);
tvSelectedItemPreview = findViewById(R.id.selectedItemPreview);
// List of items to choose from
String[] listItems = {"Android Development", "Web Development", "Machine Learning"};
bOpenAlertDialog.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v) {
// AlertDialog builder instance to build the alert dialog
AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this)
.setIcon(R.mipmap.ic_launcher_round)
.setTitle("Choose an Item");
// Build the alert dialog with single-choice items
alertDialog.setSingleChoiceItems(listItems, selectedItemIndex, (dialog, which) -> {
// Update the selected item index
selectedItemIndex = which;
// Update the TextView to show the selected item
tvSelectedItemPreview.setText("Selected Item is:\n" + listItems[which]);
// Dismiss the dialog
dialog.dismiss();
});
// Create and show the AlertDialog
AlertDialog customAlertDialog = alertDialog.create();
customAlertDialog.show();
}
});
}
}
package org.geeksforgeeks.demo
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
private lateinit var bOpenAlertDialog: Button
private lateinit var tvSelectedItemPreview: TextView
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
bOpenAlertDialog = findViewById(R.id.openAlertDialogButton)
tvSelectedItemPreview = findViewById(R.id.selectedItemPreview)
// single item array instance to store which element
// is selected by user initially it should be set to
// zero meaning none of the element is selected by default
val checkedItem = intArrayOf(-1)
bOpenAlertDialog.setOnClickListener {
// AlertDialog builder instance to build the alert dialog
val alertDialog = AlertDialog.Builder(this)
// set the custom icon to the alert dialog
.setIcon(R.mipmap.ic_launcher_round)
// title of the alert dialog
.setTitle("Choose an Item")
val listItems = arrayOf("Android Development", "Web Development", "Machine Learning")
// the function setSingleChoiceItems is the function which
// builds the alert dialog with the single item selection
alertDialog.setSingleChoiceItems(listItems, checkedItem[0]) { dialog, which ->
// update the selected item which is selected by the
// user so that it should be selected when user opens
// the dialog next time and pass the instance to setSingleChoiceItems method
checkedItem[0] = which
// now also update the TextView which previews the selected item
tvSelectedItemPreview.text = buildString {
append("Selected Item is :\n")
append(listItems[which])
}
// when selected an item the dialog should be closed
// with the dismiss method
dialog.dismiss()
}
// create and build the AlertDialog instance with the
// AlertDialog builder instance
val customAlertDialog = alertDialog.create()
// show the alert dialog when the button is clicked
customAlertDialog.show()
}
}
}