在上一遍文章介绍加载字体库来实现LCD显示数字，本篇介绍使用源码来实现，动手自己写源码。在UI下QLCDNumber控件实现了LCD数字显示，观看该控件的源码，实现自己的LCD数字显示。

首先定义一个类，例如“LCDNumberItem”继承QQuickPaintedItem类。h文件如下所示：主要是仿照QLCDNumber控件

#ifndef LCDNUMBERITEM_H

#define LCDNUMBERITEM_H

 
#include <QtQuick/QQuickPaintedItem>
 
#include <QBitArray>
 
class LCDNumberItem :  public QQuickPaintedItem
 
{
 
    Q_OBJECT
 
    Q_PROPERTY(bool smallDecimalPoint READ smallDecimalPoint WRITE setSmallDecimalPoint)
 
    Q_PROPERTY(int digitCount READ digitCount WRITE setDigitCount)
 
    Q_PROPERTY(Mode mode READ mode WRITE setMode)
 
    Q_PROPERTY(SegmentStyle segmentStyle READ segmentStyle WRITE setSegmentStyle)
 
    Q_PROPERTY(double value READ value WRITE display)
 
    Q_PROPERTY(int intValue READ intValue WRITE display)
 
public:
 
     LCDNumberItem(QQuickItem *parent = 0);
 
 
     ~LCDNumberItem();
 
     enum Mode {
 
         Hex, Dec, Oct, Bin
 
     };
 
     Q_ENUM(Mode)
 
     enum SegmentStyle {
 
        Outline , Filled, Flat
 
     };
 
     Q_ENUM(SegmentStyle)
 
     bool smallDecimalPoint() const;
 
     int digitCount() const;
 
     void setDigitCount(int nDigits);
 
 
     bool checkOverflow(double num) const;
 
     bool checkOverflow(int num) const;
 
 
     Mode mode() const;
 
     void setMode(Mode);
 
 
     SegmentStyle segmentStyle() const;
 
     void setSegmentStyle(SegmentStyle);
 
 
     double value() const;
 
     int intValue() const;
 
     void paint(QPainter *painter);
 
 
public Q_SLOTS:
 
    void display(const QString &str);
 
    void display(int num);
 
    void display(double num);
 
    void setHexMode();
 
    void setDecMode();
 
    void setOctMode();
 
    void setBinMode();
 
    void setSmallDecimalPoint(bool);
 
signals:
 
    void overflow();
 
public slots:
 
private:
 
    void init();
 
    void internalSetString(const QString& s);
 
    void drawString(const QString& s, QPainter &, QBitArray * = 0, bool = true);
 
    void drawDigit(const QPoint &, QPainter &, int, char, char = ' ');
 
    void drawSegment(const QPoint &, char, QPainter &, int, bool = false);
 
 
private:
 
    int ndigits;
 
    double val;
 
    uint base : 2;
 
    uint smallPoint : 1;
 
    uint fill : 1;
 
    uint shadow : 1;
 
    QString digitStr;
 
    QBitArray points;
 
};
 
 
#endif // LCDNUMBERITEM_H
 
 
实现文件基本和QLCDNumber控件差不多，本人还在完善中，争取实现更换颜色。在使用之前要注册一下：
 
qmlRegisterType<LCDNumberItem>("LCDNumberItem", 1, 0, "LCDNumberItem");
 
初步显示效果如下：