How to do a color animation of a QLineEdit background

[JesusM]

Hi, I want to change the background of a QLineEdit in order to provide feedback to the user so, I change it to green if the text introduced is correct and red if it's incorrect but, I don't want the color to persist all the time. I just want to change the color 1 second and then come back to the default color background.

How can I do it?. I was thinking about using QPropertyAnimation but I read It doesn't accept QString as property for animation.

Thanks.

[jsulm]

@JesusM said in How to do a color animation of a QLineEdit background:

but I read It doesn't accept QString as property for animation

You want to animate color not string, so no problem. You need to anymate background color.

[sierdzio]

QPropertyAnimation is based on QVariantAnimation, which does support QColor: https://doc.qt.io/qt-5/qvariantanimation.html. You can add custom types there as well (including QString), if you want to - check the example in class description.

[JesusM]

@jsulm oh, I thought what I had to animate was the stylesheet so I needed to introduce a QString. I will try that.

Thanks

[JesusM]

@sierdzio ok, the answer I found it's a bit old so now It seems I can use also QString. I will try.
Thanks!

[sierdzio]

You can set QLineEdit background using setPalette():

const QColor(Qt::Red);
QPalette palette(widget->palette());
palette.setBrush(QPalette::Button, QBrush(color));
palette.setBrush(QPalette::Base, QBrush(color));
widget->setPalette(palette);

Stylesheet is an option, too, but in this case seems like an overkill (and will likely be slower).

[JesusM]

@sierdzio but I need to do it with the QPropertyAnimation so I cant use QPalette as QVariant as it is not supported. I tried this:

checkIaAnimation = new QPropertyAnimation(ui->IaValue,"palette",this);
    checkIaAnimation->setDuration(1000);
    checkIaAnimation->setStartValue(QColor(Qt::white));
    checkIaAnimation->setEndValue(QColor(Qt::green));
    checkIaAnimation->setDirection(QPropertyAnimation::Forward);
    checkIaAnimation->start();

It doesn't crash but It does nothing, as is logical, because I am not specifying which color of the palette I want to change (background) but I don't know how to specify it.

[sierdzio]

Ah, right, makes sense. QPalette is not even a QObject so it does not have properties.

So I think that leaves 2 options:

• write custom interpolator for QPaletter and register it with qRegisterAnimationInterpolator and your current code should start working
• subclass QLineEdit and add a QColor property that will update the background palette when modified, then animate that property

[Devopia53]

@JesusM

In that case, QTimer is appropriate, but if you need animation, you can use QTimeLine as well. like this:

    auto    timeLine = new QTimeLine(1000, this);
    timeLine->setFrameRange(0, 255);
    connect(timeLine, &QTimeLine::frameChanged, [=](int frame){
        auto    p = ui->IaValue->palette();
        p.setBrush(QPalette::Base, QBrush(QColor(frame, frame, frame)));
       ui->IaValue->setPalette(p);
    });
    connect(timeLine, &QTimeLine::finished, timeLine, &QTimeLine::deleteLater);
    timeLine->start();

[sierdzio]

Yep, that's also a neat idea.

@Devopia53 said in How to do a color animation of a QLineEdit background:

connect(timeLine, &QTimeLine::frameChanged, [=](int frame){

There should be a control object for this labda, so:

 connect(timeLine, &QTimeLine::frameChanged, this, [=](int frame){

[anil_arise]

@JesusM May be like that type result ::

connect(ui->lineEdit,SIGNAL(textChanged(QString)),this,SLOT(ChangeColor(QString)));

ChangeColor(QString text)
{
if(text.size()==0)
ui->lineEdit->setStyleSheet("background-color:none; color:none;");
else if(text.size()>10)
ui->lineEdit->setStyleSheet("background-color:rgb(255,0,0); color:rgb(255,255,255);");
else
ui->lineEdit->setStyleSheet("background-color:rgb(0,170,0); color:rgb(255,255,0);");

}

[JesusM]

Thanks all of you. Your answers gave me the solution! Now It works fine!