QLabel设置图像的方法+绘制文本换行显示

news2024/11/13 14:42:11

1、QLabel设置图像有两种方法

(1) void setPicture(const QPicture &);

(2) void setPixmap(const QPixmap &);

QPicture和QPixmap都是继承于QPaintDevice，它们都可以通过加载图片的方式获取：bool load(QIODevice *dev, const char *format = nullptr)，也可以通过QPainter上绘制。

2、QPainter绘制文本换行显示

void drawText(const QRect &r, int flags, const QString &text, QRect *br = nullptr)

在设置第二个参数flags时，使用Qt::TextWrapAnywhere 即可使文本换行显示。

3、核心代码

(1) LabelEx.h

#ifndef LABELEX_H
#define LABELEX_H

#include <QLabel>

const QString kText = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

class LabelEx : public QLabel
{
    Q_OBJECT
public:
    explicit LabelEx(QWidget *parent = nullptr);
    ~LabelEx();
    
protected:
    void paintEvent(QPaintEvent *event) Q_DECL_OVERRIDE;
};

#endif // LABELEX_H

(2) LabelEx.cpp

#include "LabelEx.h"
#include <qpainter.h>

LabelEx::LabelEx(QWidget *parent) : QLabel(parent)
{
}

LabelEx::~LabelEx()
{
}

void LabelEx::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    QPainter painter(this);
    painter.setRenderHint(QPainter::TextAntialiasing);
    
    painter.fillRect(rect(), QColor(255, 160, 160));
    painter.drawText(rect(), Qt::AlignLeft |Qt::AlignTop |Qt::TextWrapAnywhere, kText);
}

(3) LabelTestDlg.h

#ifndef LABELTESTDLG_H
#define LABELTESTDLG_H

#include <QDialog>
#include "LabelEx.h"

class LabelTestDlg : public QDialog
{
    Q_OBJECT    
public:
    LabelTestDlg(QWidget *parent = nullptr);
    ~LabelTestDlg();
    
private:
    void init();
    
private:
    QLabel  *m_lb1 = nullptr;
    QLabel  *m_lb2 = nullptr;
    LabelEx *m_lb3 = nullptr;
};
#endif // LABELTESTDLG_H

(4) LabelTestDlg.cpp

#include "LabelTestDlg.h"
#include <qpicture.h>
#include <qpainter.h>
#include <qboxlayout.h>

LabelTestDlg::LabelTestDlg(QWidget *parent)
    : QDialog(parent)
{
    init();
}

LabelTestDlg::~LabelTestDlg()
{
}

void LabelTestDlg::init()
{
    setWindowTitle("Label测试");
    
    m_lb1 = new QLabel(this);
    m_lb2 = new QLabel(this);
    m_lb3 = new LabelEx(this);
    
    m_lb1->setFixedSize(150, 300);    
    m_lb2->setFixedSize(150, 300);    
    m_lb3->setFixedSize(150, 300);
    
    QPicture pic;
    QPainter painter1(&pic);
    painter1.fillRect(m_lb1->rect(), QColor(160, 255, 160));
    painter1.drawText(m_lb1->rect(), Qt::AlignLeft |Qt::AlignTop |Qt::TextWrapAnywhere, kText);
    m_lb1->setPicture(pic);
    
    QPixmap pix(m_lb2->size());
    pix.fill(QColor(160, 160, 255));
    QPainter painter2(&pix);
    painter2.drawText(m_lb2->rect(), Qt::AlignLeft |Qt::AlignTop |Qt::TextWrapAnywhere, kText);
    m_lb2->setPixmap(pix);
    
    QHBoxLayout *lay = new QHBoxLayout(this);
    lay->setContentsMargins(16, 16, 16, 16);
    lay->setSpacing(16);
    lay->addWidget(m_lb1);
    lay->addWidget(m_lb2);
    lay->addWidget(m_lb3);
}