qt学习笔记（四） qt编程时遇到的问题的总结

 

qt学习笔记（四） qt编程时遇到的问题的总结

分类： 编程语言 2011-11-27 17:27 3742人阅读 评论(2) 收藏 举报

qt 编程 class object

1、设置qt widget全屏显示

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    //w.show();
    w.showFullScreen();
    return a.exec();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    //w.show();
    w.showFullScreen();
    return a.exec();
}

2、获取屏幕分辨率

#include <QDesktopWidget>
#Include <QApplication>
void MainWindow::GetScreenInfo()
{
    QDesktopWidget* desktopWidget = QApplication::desktop();
    //获取可用桌面大小
    //QRect deskRect = desktopWidget->availableGeometry();
    //获取设备屏幕大小
    QRect screenRect = desktopWidget->screenGeometry();

    sceenSizeX = screenRect.width();
    sceenSizeY = screenRect.height();

    //获取系统设置的屏幕个数（屏幕拷贝方式该值为1）
    //g_nScreenCount = desktopWidget->screenCount();
}

#include <QDesktopWidget>
#Include <QApplication>
void MainWindow::GetScreenInfo()
{
    QDesktopWidget* desktopWidget = QApplication::desktop();
    //获取可用桌面大小
    //QRect deskRect = desktopWidget->availableGeometry();
    //获取设备屏幕大小
    QRect screenRect = desktopWidget->screenGeometry();

    sceenSizeX = screenRect.width();
    sceenSizeY = screenRect.height();

    //获取系统设置的屏幕个数（屏幕拷贝方式该值为1）
    //g_nScreenCount = desktopWidget->screenCount();
}

3、QGraphicsView添加背景图片：1

view = new QGraphicsView;
scene = new QGraphicsScene(0,0,800,480);
QPixmap pixmap(":/gear.png");
scene->addPixmap(pixmap);
view->setScene(scene);

    view = new QGraphicsView;
    scene = new QGraphicsScene(0,0,800,480);
    QPixmap pixmap(":/gear.png");
    scene->addPixmap(pixmap);
    view->setScene(scene);

3、QGraphicsView添加背景图片：2

view->setBackgroundBrush(QImage(":/gear.png"));

view->setBackgroundBrush(QImage(":/gear.png"));

前提是将gear.png加入到资源中

4、设置无边框（标题栏）的应用程序

QApplication a(argc, argv);
MainWindow w;

w.setWindowOpacity(1);
w.setWindowFlags(Qt::FramelessWindowHint);
w.setAttribute(Qt::WA_TranslucentBackground);
w.show();

    QApplication a(argc, argv);
    MainWindow w;

    w.setWindowOpacity(1);
    w.setWindowFlags(Qt::FramelessWindowHint);
    w.setAttribute(Qt::WA_TranslucentBackground);
    w.show();

5 、QGraphicsPixmapItem，显示图片Item

scene = new QGraphicsScene(0,0,800,480);

QGraphicsPixmapItem *pixmapItem = new QGraphicsPixmapItem(QPixmap(":/gear.png"));
pixmapItem->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable);
scene->addItem(pixmapItem);

    scene = new QGraphicsScene(0,0,800,480);

    QGraphicsPixmapItem *pixmapItem = new QGraphicsPixmapItem(QPixmap(":/gear.png"));
    pixmapItem->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable);
    scene->addItem(pixmapItem);

6 Q_OBJECT 问题

class NodeUI : public QGraphicsPixmapItem
{
    Q_OBJECT
...
}

class NodeUI : public QGraphicsPixmapItem
{
    Q_OBJECT
...
}

编译不通过

class NodeUI : public QGraphicsPixmapItem ,public QObject
{
    Q_OBJECT
...
}

class NodeUI : public QGraphicsPixmapItem ,public QObject
{
    Q_OBJECT
...
}

依然不通过

class NodeUI : public QObject,public QGraphicsPixmapItem
{
    Q_OBJECT
...
}

class NodeUI : public QObject,public QGraphicsPixmapItem
{
    Q_OBJECT
...
}

编译通过！

7 ，编译出错：error: passing 'const QPointF' as 'this' argument of 'QPointF& QPointF::operator=(const QPointF&)' discards qualifiers

NodeUI *MainWindow::selectedNodeUI() const
{
    QList<QGraphicsItem *> items = scene->selectedItems();
    if (items.count() == 1) {
        mmyPos = items.first()->pos();
        //QPointF myPos = pos;
        //mmyPos = pos.toPoint();
        //mmyPos.setX(x);
        //mmyPos.setY(y);
        //mmyPos = QPoint(x,y);
        //qDebug()<<"items.x:"<<nodePos.x()<<"items.y:"<<nodePos.y();
        return dynamic_cast<NodeUI *>(items.first());
    } else {
        return 0;
    }
}

NodeUI *MainWindow::selectedNodeUI() const
{
    QList<QGraphicsItem *> items = scene->selectedItems();
    if (items.count() == 1) {
        mmyPos = items.first()->pos();
        //QPointF myPos = pos;
        //mmyPos = pos.toPoint();
        //mmyPos.setX(x);
        //mmyPos.setY(y);
        //mmyPos = QPoint(x,y);
        //qDebug()<<"items.x:"<<nodePos.x()<<"items.y:"<<nodePos.y();
        return dynamic_cast<NodeUI *>(items.first());
    } else {
        return 0;
    }
}

修改为如下，问题解决；

NodeUI *MainWindow::selectedNodeUI()
{
    QList<QGraphicsItem *> items = scene->selectedItems();
    if (items.count() == 1) {
        mmyPos = items.first()->pos();
        //QPointF myPos = pos;
        //mmyPos = pos.toPoint();
        //mmyPos.setX(x);
        //mmyPos.setY(y);
        //mmyPos = QPoint(x,y);
        //qDebug()<<"items.x:"<<nodePos.x()<<"items.y:"<<nodePos.y();
        return dynamic_cast<NodeUI *>(items.first());
    } else {
        return 0;
    }
}

NodeUI *MainWindow::selectedNodeUI()
{
    QList<QGraphicsItem *> items = scene->selectedItems();
    if (items.count() == 1) {
        mmyPos = items.first()->pos();
        //QPointF myPos = pos;
        //mmyPos = pos.toPoint();
        //mmyPos.setX(x);
        //mmyPos.setY(y);
        //mmyPos = QPoint(x,y);
        //qDebug()<<"items.x:"<<nodePos.x()<<"items.y:"<<nodePos.y();
        return dynamic_cast<NodeUI *>(items.first());
    } else {
        return 0;
    }
}

8，QMap遍历问题

QMap插入时的顺序和最后得到的QMap遍历顺序可能是不通的，QMap所谓的有序是按照key内部自动升序，在不同的电脑上，顺序都可能不同。

对顺序有要求时，不可以用QMap，QHash就更不用说了。

待续。。