Qt之自定义界面组件 一

通过qt中的painter绘图事件绘制一个电池电量图的变化。效果如下图

创建一个基于界面widget工程，在wdiget界面添加一个widget界面,将添加的widget界面的类提升为Tbattery.在Tbattery类中重写painEvent电池电量代码

文件目录结构

主要部分代码

//Tbattery.cpp
#include "tbattery.h"
#include<QPainter>
#include<QPaintEvent>
Tbattery::Tbattery(QWidget *parent)
    : QWidget{parent}
{

}

int Tbattery::warningLevel() const
{
    return m_warningLevel;
}

void Tbattery::setWarningLevel(int newWarningLevel)
{

    m_warningLevel=newWarningLevel;
       repaint();
}

int Tbattery::powerLevel() const
{
    return m_powerLevel;
}

void Tbattery::setPowerLevel(int newPowerLevel)
{
    m_powerLevel = newPowerLevel;
    repaint();
}

void Tbattery::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    QRect rect(0,0,width(),height());
    painter.setViewport(rect);//设置屏幕坐标


     painter.setWindow(0,0,120,50);//设置逻辑坐标
     painter.setRenderHint(QPainter::TextAntialiasing);
     painter.setRenderHint(QPainter::Antialiasing);


    QPen pen(colorBorder);
    pen.setWidth(1);
    pen.setStyle(Qt::SolidLine);
    pen.setCapStyle(Qt::FlatCap);
    pen.setJoinStyle(Qt::BevelJoin);
    painter.setPen(pen);
    QBrush brush(colorBackgroud);
    brush.setStyle(Qt::SolidPattern);
    painter.setBrush(brush);

    //绘制边框

     rect.setRect(1,1,109,48);
     painter.drawRect(rect);

    brush.setColor(colorBorder);
    painter.setBrush(brush);
    rect.setRect(110,15,10,20);
    painter.drawRect(rect);

    if(m_powerLevel>m_warningLevel)
    {
        brush.setColor(colorPower);
        pen.setColor(colorPower);
    }
    else
    {
        brush.setColor(colorWarning);
        pen.setColor(colorWarning);
    }
    painter.setPen(pen);
    painter.setBrush(brush);

    if(m_powerLevel>0)
    {
        rect.setRect(5,5,m_powerLevel,40);
        painter.drawRect(rect);
    }
    QString powStr=QString::asprintf("%d%%",m_powerLevel);
    QFontMetrics textSize(this->font());
    QRect textRect=textSize.boundingRect(powStr);
    painter.setFont(this->font());
    pen.setColor(colorBorder);
    painter.setPen(pen);
    painter.drawText(55-textRect.width()/2,25+textRect.height()/2,powStr);
    event->accept();
}
//Tbattery.h/


#ifndef TBATTERY_H
#define TBATTERY_H

#include <QWidget>

class Tbattery : public QWidget
{
    Q_OBJECT
public:
    explicit Tbattery(QWidget *parent = nullptr);
    int warningLevel() const;
    void setWarningLevel(int newWarningLevel);

    int powerLevel() const;
    void setPowerLevel(int newPowerLevel);

private:
    QColor colorBackgroud=Qt::white;
    QColor colorBorder=Qt::black;
    QColor colorPower=Qt::green;
    QColor colorWarning=Qt::red;
    int m_powerLevel  = 60;
    int m_warningLevel = 20;

signals:

    // QWidget interface
protected:
    virtual void paintEvent(QPaintEvent *event) override;
};



#endif // TBATTERY_H