Difference between revisions of "Android-app-using-Kotlin/C2/Adding-Radio-Buttons/English"

Learning Objectives

• Add a Radio Group and Radio buttons
• And run the Kotlin App to see the output in an Android phone

System requirement

• Ubuntu Linux 16.04 operating system
• Android Studio version 3.x and
• Android Phone with minimum of Android OS version 4.03

Pre-requisites

• Java programming language and
• Android Studio

If not, then go through the relevant tutorials on this website.

The label Gender will be created using TextView tool.

Point to the left panel

Click on RegistrationForm

Or you can click on Open an existing Android Studio Project.

And then select the RegistrationForm project from the saved location.

Point to the left panel >> Click on RegistrationForm

Now we will add some more tools.

Once done, we can add the new tools .

Change the text attribute to Gender.

Click on this TextView and change its text attribute to Gender.

Aligning the tools in the layout editor.

• Radio group can hold the Radio Buttons.
• When radio buttons are placed inside a Radio Group, the user can only select one button at one time.
• We can have any number of Radio Groups as per the requirement.

select and drag Radio Group

Now select and drag Radio Group and place it below the Gender TextView.

So first, we need to give a unique ID.

Otherwise, the tool is not able to attach to other tools via constraints.

In the Attributes window, type “genderRadioGroup” in ID field and press Enter.

Aligning the tools in the layout editor

Point to the tree heirarchy

Drag it to the Component Tree panel and release it on the genderRadioGroup.

Note that it should come under the hierarchy of genderRadioGroup and not under ConstraintLayout.

Change second RadioButton text attribute to “Female”.

Likewise, change the text attribute to “Female” for the second radio button.

Now click on the top constraint of the button.

Then drag and attach to the bottom of Radio Group to place it properly.

Declaring variables in kotlin

Here, Int data type is assigned by default to a variable x.

val x =5

The value 5 is a constant when the variable is declared using ‘val’ keyword.

val x: Int =5

We are declaring a constant value 5 to the variable x of type Int.

Otherwise, we can say

val x:Int

and assign the value in the next line as

x=5

var gender = " "

var genderId = genderRadioGroup.checkedRadioButtonId

if(genderId != -1){

val selected_gender : RadioButton = findViewById(genderId)

gender = selected_gender.text.toString()

}

First we will create a new variable to store the gender information.

Type this line of code below the code var name = " "

In setOnClickListener function, after the Toast method, write the below code.

<<code>>

This function returns the id of the Radio Button which is selected from the Radio Group.

The Id is stored in the variable genderId.

This function returns -1 when no radio button is selected.

The Radio Button value is stored in a variable selected_gender by the method findViewById().

findViewById() method returns the view of which ID is passed as argument.

This line extracts the text of the selected radio button and stores it in the gender variable.

This new data can now be accessed inside SecondActivity.kt

Let us resize the TextView to add the gender information.

var obtainedGender = ""

This will store the gender data from FirstActivity in obtainedGender variable.

Show the demo of the run window

Click on the Play button to run the Kotlin app.

Select gender.

Click on the Click Here button.

Enter your name and select any one of the gender radio buttons.

Click on the Click Here button.

Summary

• Add Radio Groups and Radio Buttons
• Run the Kotlin app to see the output in an Android phone

Assignment

1. Add one more radio button to the Radio Group and change the text attribute as “Others”.
2. Run the Kotlin app to check the output.

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Acknowledgement

[1]

More information on this mission is available at this link.

And this is Nirmala Venkat along with the Spoken Tutorial team from IIT Bombay, signing off.

Thanks for watching.