英文:
How to slow down printing progress values on a label?
问题
我正在使用一个标签来在Qt C++中作为进度条的一部分打印0到100。我使用下面的代码来实现，但它执行得太快了：
for (i = 0; i <= 100; i++){data = QString::number(i);ui->label_29->setText(data + "%");}
我尝试使用sleep()函数，但它会冻结exe文件，无法运行。我在考虑使用线程，但我不知道如何做。
英文:
I'm using a label to print 0 to 100 as a part of an progress bar in Qt C++. I use the code below to do it but it executes too fast:
for (i = 0; i <= 100; i++){data = QString::number(i);ui->label_29->setText(data + "%");}
I tried to use sleep() function but it froze the exe file and it couldn't run. I'm thinking of using a thread but I don't know how.
答案1
得分: 6
// 使用Qt的QTimer类在每个步骤之间设置延迟以更新进度条，而不会冻结GUI。class ProgressBarExample : public QObject{Q_OBJECTpublic:ProgressBarExample() : i(0){// 创建并配置标签label = new QLabel();label->setAlignment(Qt::AlignCenter);label->setFixedSize(200, 30);// 创建QTimer对象并将其超时信号连接到updateProgressBar槽timer = new QTimer(this);connect(timer, &QTimer::timeout, this, &ProgressBarExample::updateProgressBar);// 设置更新之间的所需间隔（以毫秒为单位）int interval = 100; // 根据您的需求调整此值timer->setInterval(interval);// 启动定时器timer->start();// 显示标签label->show();}private slots:void updateProgressBar(){if (i > 100) {// 如果进度达到100％，则停止定时器timer->stop();return;}QString data = QString::number(i);label->setText(data + "%");i++; // 增加计数器}private:QLabel* label;QTimer* timer;int i;};int main(int argc, char *argv[]){QApplication app(argc, argv);ProgressBarExample example;return app.exec();}
英文:
To update the progress bar with a delay between each step without freezing the GUI, you can utilize Qt's QTimer class to schedule the updates at regular intervals.
Here's an example:
#include <QApplication>#include <QLabel>#include <QTimer>class ProgressBarExample : public QObject{Q_OBJECTpublic:ProgressBarExample() : i(0){// Create and configure the labellabel = new QLabel();label->setAlignment(Qt::AlignCenter);label->setFixedSize(200, 30);// Create the QTimer object and connect its timeout signal to the updateProgressBar slottimer = new QTimer(this);connect(timer, &QTimer::timeout, this, &ProgressBarExample::updateProgressBar);// Set the desired interval (in milliseconds) between updatesint interval = 100; // Adjust this value as per your requirementtimer->setInterval(interval);// Start the timertimer->start();// Show the labellabel->show();}private slots:void updateProgressBar(){if (i > 100) {// Stop the timer if the progress reaches 100%timer->stop();return;}QString data = QString::number(i);label->setText(data + "%");i++; // Increment the counter}private:QLabel* label;QTimer* timer;int i;};int main(int argc, char *argv[]){QApplication app(argc, argv);ProgressBarExample example;return app.exec();}#include "main.moc"
答案2
得分: 0
从Qt文档的QThread部分：
>注意：通常情况下，wait() 和 sleep() 函数应该是不必要的，因为Qt是一个事件驱动的框架。可以考虑使用 finished() 信号来代替 wait()。可以考虑使用 QTimer 来代替 sleep() 函数。
QThread::sleep：
>如果需要等待特定条件发生，请避免使用此函数。相反，连接一个槽到指示变化的信号，或者使用事件处理程序...
而且，由于您的目标是：
>我正在使用标签来打印0到100作为进度条的一部分
以下是实现这一目标的两种方法：
解决方案1：
您可以使用 QLabel 模仿进度条，并通过使用 QTimer 将其连接到一个 lambda 函数，该函数会增加标签上显示的值，从而使进度可见。我使用了 100ms 的超时，我正在循环进行进度，您可以在某个条件下使用 QTimer::stop 来停止它。
这是一个最小化的可复现示例：
#include <QApplication>#include <QTimer>#include <QLabel>int main(int argc,char*argv[]){QApplication a(argc, argv);QLabel *l = new QLabel();l->setText("0");l->setAlignment(Qt::AlignCenter);QTimer *t = new QTimer();t->connect(t,&QTimer::timeout,[=](){l->setText(QString::number((l->text().toInt()+1)%100));});t->start(100);l->show();return a.exec();}
这是它的外观：
解决方案2：
要显示进度，Qt 提供了 QProgressBar，以下是如何在上述解决方案中使用它的方法：
#include <QApplication>#include <QProgressBar>#include <QTimer>int main(int argc,char*argv[]){QApplication a(argc, argv);QProgressBar *p = new QProgressBar();p->setRange(0,100);p->setValue(0);p->setOrientation(Qt::Horizontal);QTimer *t = new QTimer();t->connect(t,&QTimer::timeout,[=](){p->setValue((p->value()+1)%p->maximum());});t->start(100);p->show();return a.exec();}
这是它的外观：
英文:
From Qt documentation of QThread:
>Note: wait() and the sleep() functions should be unnecessary in general, since Qt is an event-driven framework. Instead of wait(), consider listening for the finished() signal. Instead of the sleep() functions, consider using QTimer.
QThread::sleep:
>Avoid using this function if you need to wait for a given condition to change. Instead, connect a slot to the signal that indicates the change or use an event handler...
And since your goal is:
>I'm using a label to print 0 to 100 as a part of a progress bar
Here are 2 ways you can achieve that:
Solution 1:
You can use a QLabel to mimic a progress bar, and make it possible to see it progressing, by using a QTimer, connecting its timeout signal to a lambda that incrementing the value displayed on the label itself.
I used a timeout of 100ms, and I'm looping the progress, you can tweak that to make it stop at a 100 by using QTimer::stop at some condition.
Here's a minimal reproducible example:
#include <QApplication>#include <QTimer>#include <QLabel>int main(int argc,char*argv[]){QApplication a(argc, argv);QLabel *l = new QLabel();l->setText("0");l->setAlignment(Qt::AlignCenter);QTimer *t = new QTimer();t->connect(t,&QTimer::timeout,[=](){l->setText(QString::number((l->text().toInt()+1)%100));});t->start(100);l->show();return a.exec();}
Here's how it looks:
Solution 2:
To display a progress, Qt offers QProgressBar, here's how you can use it in the above solution:
#include <QApplication>#include <QProgressBar>#include <QTimer>int main(int argc,char*argv[]){QApplication a(argc, argv);QProgressBar *p = new QProgressBar();p->setRange(0,100);p->setValue(0);p->setOrientation(Qt::Horizontal);QTimer *t = new QTimer();t->connect(t,&QTimer::timeout,[=](){p->setValue((p->value()+1)%p->maximum());});t->start(100);p->show();return a.exec();}
Here's how it looks:
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