8.Draw

本例实现2个功能:1）画多条线   2)自定义按钮

 

#ifndef MYBUTTON_H
#define MYBUTTON_H

#include <QWidget>

class MyButton : public QWidget
{
    Q_OBJECT
public:
    explicit MyButton(QWidget *parent = 0);
    MyButton(const QString& text, QWidget* parent = 0);

    QRect _rect;
    QString _text;
    bool _pressed;
    void mousePressEvent(QMouseEvent *);
    void mouseReleaseEvent(QMouseEvent *);

    void paintEvent(QPaintEvent *);

signals:
    void clicked();

public slots:

};

#endif // MYBUTTON_H

#include "MyButton.h"
#include <QPainter>
#include <QMouseEvent>
MyButton::MyButton(QWidget *parent) :
    QWidget(parent), _rect(0, 0, 100, 30), _text(QString())
{
    _pressed = false;
    this->setGeometry(_rect);
}

MyButton::MyButton(const QString &text, QWidget *parent):
    QWidget(parent), _text(text), _rect(0, 0, 100, 30)
{
    _pressed = false;
    this->setGeometry(_rect);
}

void MyButton::mousePressEvent(QMouseEvent *)
{
    _pressed = true;
    update();
}

void MyButton::mouseReleaseEvent(QMouseEvent *ev)
{
    _pressed = false;
    update();

    if(_rect.contains(ev->pos()))
        emit clicked();
    // callback handler
}
void MyButton::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    if(_pressed)
        p.setBrush(Qt::yellow);
    else
        p.setBrush(Qt::darkGray);
    p.drawRect(_rect);
    p.drawText(_rect, _text, QTextOption(Qt::AlignCenter));
}

#ifndef MYWIDGET_H
#define MYWIDGET_H

#include <QWidget>
#include "MyButton.h"

class MyWidget : public QWidget
{
    Q_OBJECT
public:
    explicit MyWidget(QWidget *parent = 0);

    MyButton* button;

    void paintEvent(QPaintEvent *);

    void mousePressEvent(QMouseEvent *);
    void mouseReleaseEvent(QMouseEvent *);
    void mouseMoveEvent(QMouseEvent *);

    QVector< QVector<QPoint> > _lines;

signals:

public slots:
    void slotButtonClicked();
};

#endif // MYWIDGET_H

 

#include "MyWidget.h"
#include <QPainter>
#include <QPixmap>
#include <QMouseEvent>
#include <QDebug>

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{
    button = new MyButton("MyButton", this);
    connect(button, SIGNAL(clicked()), this, SLOT(slotButtonClicked()));

    button->setGeometry(30, 30, 100, 30);
}

void MyWidget::slotButtonClicked()
{
    qDebug() << "button is clicked";
}

void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    for(int i=0; i<_lines.size(); ++i)
    {
        const QVector<QPoint>& line = _lines.at(i);
        for(int j=0; j<line.size()-1; ++j)
        {
            p.drawLine(line.at(j), line.at(j+1));
        }
    }
}

void MyWidget::mouseMoveEvent(QMouseEvent *ev)
{
    if(_lines.size() == 0)
    {
        QVector<QPoint> line;
        _lines.append(line);
    }

    QVector<QPoint>& lastLine = _lines.last();
    lastLine.append(ev->pos());

    update();
}
void MyWidget::mousePressEvent(QMouseEvent *ev)
{
    QVector<QPoint> line;
    _lines.append(line);

    QVector<QPoint>& lastLine = _lines.last();
    lastLine.append(ev->pos());
}
void MyWidget::mouseReleaseEvent(QMouseEvent *ev)
{
    QVector<QPoint>& lastLine = _lines.last();
    lastLine.append(ev->pos());
}

#include <QApplication>
int main(int argc, char** argv)
{
    QApplication app(argc, argv);

    MyWidget w;
    w.show();

    return app.exec();
}