How to Set a Default Value for a Radio Button Group in a Qt Widget Application in C++

In this article, we show how to set a default value for a radio button group in a Qt widget application in C++.

An example of a group of radio buttons is shown below with the first choice, Mastercard, selected as the default value for the group.

This is shown below.

MasterCard
Visa
American Express
Discover

So how do we select a default value for a radio button group?

So in order to set the default value for a radio button group in a Qt widget applicaiton, we go to the "widget.cpp" header file and add in a line, which checks the radio button that you want selected by default.

#include "widget.h" #include "ui_widget.h" Widget::Widget(QWidget *parent) : QWidget(parent) , ui(new Ui::Widget) { ui->setupUi(this); ui->radioButton->setChecked(true); } Widget::~Widget() { delete ui; } void Widget::on_pushButton_clicked() { //Main code }

The line we add is, ui->radioButton->setChecked(true);, which uses the setChecked() function to create a default value for the radio button group.

The setChecked() function takes in the parameters of either true or false. When creating a default value, true must be passed in as its parameter.

radioButton refers to the name of the radio button that you want selected. In this case, it is the first radio button that we select as the default selected item.

Let's say there are 4 radio buttons in a certain radio button group. These 4 radio buttons have the following names: radiobutton, radiobutton_2, radiobutton_3, and radiobutton_4.

If we want to select the second radio button as the default selected radio button, then you would add the following line into code, ui->radioButton_2->setChecked(true);

If we want to select the third radio button as the default selected radio button, then you would add the following line into code, ui->radioButton_3->setChecked(true);

If we want to select the fourth radio button as the default selected radio button, then you would add the following line into code, ui->radioButton_4->setChecked(true);

Keep in mind that if you have several radio buttons groups, you can select a default value for each one. But you must make sure that each group of radio buttons is delineated in the software as its own group.

So if you have 8 radio buttons on a certain user interface in your Qt widget application and the first radio button group is radio buttons 1-4 and the second radio button group is radio buttons 5-8, then you select one of the radio buttons from 1-4 as the default value and one of the radio buttons from 5-8 as the default value.

And this is how to set a default value for a radio button group in a Qt widget application in C++.

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