一、演示效果

二、核心代码

#ifndef DynamicUnderlineLineEdit_H
#define DynamicUnderlineLineEdit_H#include <QWidget>
#include <QLineEdit>
#include <QPainter>
#include <QPaintEvent>
#include <QFocusEvent>
#include <QTimer>
#include <QColor>
#include <QPointF>
#include <QPalette>//动态下划线单行文本框：Dynamic Underline LineEdit
class DynamicUnderlineLineEdit : public QLineEdit
{Q_OBJECT
public:explicit DynamicUnderlineLineEdit(QWidget *parent = nullptr);explicit DynamicUnderlineLineEdit(const QString &text, QWidget *parent = nullptr);void setLinePen( const QPen &focusInPen,const QPen &focusOutPen = QPen(QBrush(QColor(66,66,66)),2)); // 设置线条的绘制画笔，参数：获取焦点的绘制画笔，失去焦点的绘制画笔void setTextColor(const QColor &textColor);                                 // 设置输入文字颜色void setPlaceholderTextColor(const QColor &placeholderText);                // 设置预设背景文字颜色void setLineSpeed(int speed);                                               // 设置线条填速度,越小越快，最小为1,实际使用可根据文本框的长度不同设置不同的速度以达到最佳观感private:int right_coordinate{-1};   // 线条右侧坐标QTimer *timer;QPen inactive_pen;// 未获得焦点时线条的绘制画笔QPen active_pen; // 获得焦点时线条的绘制画笔void initializeMemberVariable();private slots:void inFocus();  // 获得焦点void outFocus(); // 失去焦点protected:virtual void paintEvent(QPaintEvent *event) override;virtual void focusInEvent(QFocusEvent *event) override;  // 获取焦点事件virtual void focusOutEvent(QFocusEvent *event) override; // 失去焦点事件
};#endif // DynamicUnderlineLineEdit_H

#include "DynamicUnderlineLineEdit.h"DynamicUnderlineLineEdit::DynamicUnderlineLineEdit(QWidget *parent): QLineEdit{parent},timer{new QTimer(this)}
{initializeMemberVariable();
}
DynamicUnderlineLineEdit::DynamicUnderlineLineEdit(const QString &text, QWidget *parent): QLineEdit::QLineEdit(text,parent)
{initializeMemberVariable();
}void DynamicUnderlineLineEdit::setLinePen( const QPen &focusInPen,const QPen &focusOutPen)
{inactive_pen = focusOutPen;active_pen = focusInPen;
}void DynamicUnderlineLineEdit::setTextColor(const QColor &textColor)
{const_cast<QPalette &>(palette()).setColor(QPalette::ColorRole::Text, textColor);
}void DynamicUnderlineLineEdit::setPlaceholderTextColor(const QColor &placeholderText)
{const_cast<QPalette &>(palette()).setColor(QPalette::ColorRole::PlaceholderText, placeholderText);
}void DynamicUnderlineLineEdit::setLineSpeed(int speed)
{timer->setInterval(speed);
}void DynamicUnderlineLineEdit::initializeMemberVariable()
{setFocusPolicy(Qt::ClickFocus);timer->setInterval(12);connect(timer, &QTimer::timeout, this, &DynamicUnderlineLineEdit::inFocus);setAttribute(Qt::WA_TranslucentBackground);//背景透明setFrame(false);//无边框setTextMargins(10, 0, 0, 0);//设置文本左边距10像素inactive_pen.setColor(qRgb(66, 66, 66));inactive_pen.setWidth(2);active_pen.setColor(qRgb(0, 123, 255));active_pen.setWidth(2);
}void DynamicUnderlineLineEdit::inFocus()
{right_coordinate += 10;if (right_coordinate > width())timer->stop();update();
}void DynamicUnderlineLineEdit::outFocus()
{right_coordinate -= 10;if (right_coordinate < 0)timer->stop();update();
}void DynamicUnderlineLineEdit::paintEvent(QPaintEvent *event)
{QLineEdit::paintEvent(event);QPainter painter = QPainter(this);painter.setRenderHint(QPainter::RenderHint::Antialiasing); // 抗锯齿painter.setPen(inactive_pen); // 设置画笔颜色和线条样式painter.drawLine(0, height() - inactive_pen.width(),width(), height() - inactive_pen.width()); // 在底部画未选中时的线条painter.setPen(active_pen);painter.drawLine(-2, height() - active_pen.width(),right_coordinate, height() - active_pen.width()); // 在底部画选中时的线条
}void DynamicUnderlineLineEdit::focusInEvent(QFocusEvent *event)
{QLineEdit::focusInEvent(event);timer->disconnect();connect(timer, &QTimer::timeout, this, &DynamicUnderlineLineEdit::inFocus);timer->start();
}void DynamicUnderlineLineEdit::focusOutEvent(QFocusEvent *event)
{QLineEdit::focusOutEvent(event);timer->disconnect();connect(timer, &QTimer::timeout, this, &DynamicUnderlineLineEdit::outFocus);timer->start();
}

三、下载链接

https://download.csdn.net/download/u013083044/88864880