CheckBox

1. Definition

A CheckBox is a UI component that allows users to select or deselect one or more options.

It works like a small square box that can be checked (✓) or unchecked.

Example:

☐ Pizza
☐ Burger
☐ Sandwich

After selection:

☑ Pizza
☐ Burger
☑ Sandwich

Simple meaning:

CheckBox = A selectable box used to choose options.

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2. Purpose

CheckBox is used when users can select multiple choices.

Common uses:

App Feature	Example
Food ordering app	Select toppings
Settings screen	Enable notifications
Survey form	Select hobbies
Terms & conditions	Accept agreement

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3. Basic Syntax (XML)

Example layout:

<CheckBox
    android:id="@+id/checkPizza"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Pizza"/>

Explanation:

• id → unique identifier

• layout_width → width

• layout_height → height

• text → label shown beside checkbox

Result:

☐ Pizza

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4. Using CheckBox in Kotlin

Example inside Activity:

import android.os.Bundle
import android.widget.CheckBox
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val pizzaCheck = findViewById<CheckBox>(R.id.checkPizza)

        if (pizzaCheck.isChecked) {
            println("Pizza selected")
        }
    }
}

Explanation:

• findViewById() connects Kotlin to XML

• isChecked checks whether the box is selected

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5. Important Properties

1. text

Sets label text.

android:text="Burger"

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2. checked

Sets default selection.

android:checked="true"

Example result:

☑ Burger

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3. textColor

Changes label color.

android:textColor="#000000"

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4. textSize

Changes text size.

android:textSize="18sp"

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5. padding

Adds space inside.

android:padding="8dp"

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6. Important Methods (Kotlin)

isChecked

Checks whether checkbox is selected.

if (checkBox.isChecked) {
    println("Selected")
}

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setChecked()

Set checkbox state.

checkBox.isChecked = true

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toggle()

Switch checked/unchecked.

checkBox.toggle()

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setOnCheckedChangeListener()

Detect when user checks/unchecks.

checkBox.setOnCheckedChangeListener { _, isChecked ->
    if (isChecked) {
        println("Checked")
    } else {
        println("Unchecked")
    }
}

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7. Real-Time Examples

Example 1: Food Order App

☐ Pizza
☐ Burger
☐ Pasta

Users can choose multiple items.

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Example 2: App Settings

☑ Enable Notifications
☐ Dark Mode
☐ Auto Update

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Example 3: Terms and Conditions

☐ I agree to Terms and Conditions

Button becomes enabled only after checking.

Kotlin example:

val termsCheck = findViewById<CheckBox>(R.id.checkTerms)

termsCheck.setOnCheckedChangeListener { _, isChecked ->
    button.isEnabled = isChecked
}

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Example 4: Survey Form

Hobbies:

☐ Reading
☐ Gaming
☐ Sports
☐ Music

Multiple answers allowed.

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8. Advantages

✔ Allows multiple selections
✔ Easy for users to understand
✔ Simple to implement
✔ Common in forms and settings

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9. Disadvantages

❌ Not suitable when only one option must be selected
(Use **RadioButton instead.)

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10. One-Line Summary

CheckBox is an Android UI component that allows users to select or deselect multiple options.

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