How do I connect ComboBox and TextBrowser using PushButton-Qt? - c++

Question

I make a program that reads a file. I have a combobox that reads lines numbers: 1,6,11,..etc. I want to e.g. read lines 1-5 when line number 1 is choosen in combobox and push button is clicked (or read lines 6-10 when line 6 is choosen, end so on).
For now I have this.
int line_counter=1;
if(file.open (QIODevice::ReadOnly | QIODevice::Text))
{
while(!stream.atEnd())
{
line = stream.readLine ();
if(!line.isNull ())
{
if((line_counter%5)==1)
ui->comboBox->addItem (line);
line_counter++;
}
}
}
stream.flush ();
file.close ();
void Servers::on_pushButton_clicked()
{
if(file.open (QIODevice::ReadOnly | QIODevice::Text))
{
for(int i=line_counter;i<line_counter+5;i++)
{
ui->textBrowser->setText(stream.readLine(i));
}
}
file.close ();
}

Answer 1

You can avoid reading from file each team you want to update textBrowser if the text is already in the comboBox.
First of all connect the pushButton signal with your method:
connect(ui->pushButton, &QPushButton::clicked, this, &Servers::on_pushButton_clicked);
Then change on_pushButton_clicked like so:
void Servers::on_pushButton_clicked()
{
if(file.open (QIODevice::ReadOnly | QIODevice::Text))
{
int index = ui->comboBox->currentIndex();
int from = 5 * index;
int to = from + 5;
QTextStream stream(&file);
int lineCount = 0;
QString text;
QString line;
while (stream.readLineInto(&line)) {
if (from >= lineCount && lineCount < to) {
text += line;
text += '\n';
}
lineCount++;
}
ui->textBrowser->setText(text.toString());
}
}