QT GUI代码大全(MainWindow, QFile, QPainter, QGraphicsItem/Scene/View)

窗口设置

QMainWindow类

• QMainWindow(QWidget *parent = nullptr, Qt::WindowFlags flags = Qt::WindowFlags())

• void setCentralWidget(QWidget *widget); //set the given widget to the main window’s central widget

• void setFixedSize(int w, int h); //set the size of the widget

• void setWindowIcon(QIcon(QString filepath));

按钮和菜单

QMenuBar类

• QMenuBar *QMainWindow::menuBar() const
  返回MainWindow的menu bar
  //creates and returns an empty menu bar if the menu bar does not exist.

• QMenuBar::addMenu(QMenu *menu)

• QMenuBar::addMenu(const QString& title)

QMenu类

• addAction(QAction *action)
• addSeparator()

QAction类

可以看成是一个动作,连接到槽

• QAction(const QString &text, QObject *parent = nullptr)

• 设置快捷键

void QAction::setShortcuts(const QList<QKeySequence> &shortcuts)

• ->setStatusTip(tr("Start a new game")); 设置说明
• ->setEnabled(false) 设置按钮激活状态
• connect(aboutAction, &QAction::triggered, this, &MainWindow::about);

文件交互

QFileDialog类

用于打开文件选择窗口

QString fileName = QFileDialog::getOpenFileName(this, tr("Open File"),                                       "/home",  //文件夹目录
tr("Images (*.png *.xpm *.jpg)"));

QFileInfo类

用于获取文件的相关信息,比如后缀名等等

QString extension = fileInfo.suffix().toLower();  // 获取小写的文件后缀名

QFile类

• QFile(QString filename, QObject *parent*);
• .setFileName(filePath);

QTextStream

文本流,用于读取数据
QTextStream::QTextStream(FILE *fileHandle, QIODevice::OpenMode openMode = QIODevice::ReadWrite)

QTextStream in(&file);

• 逐行读取

while(!in.atEnd()){
    QString line = in.readLine(); // 读取一行
     ... // 逐行处理
    }
    file.close();

绘图

QPixmap类

贴图,纹理

• QPixmap::QPixmap(int width, int height)
  //注释:上面尚未fill with color

• QPixmap::QPixmap(const QString &fileName, const char *format = nullptr, Qt::ImageConversionFlags flags = Qt::AutoColor)

• void QPixmap::fill(const QColor &color = Qt::white)

QPainter类

• QPainter(QPaintDevice *device)
  例如

//QPixmap bg(TILE_SIZE, TILE_SIZE);
QPainter p(&bg);
QPainter p(this);

• setBrush(const QBrush)
• setPen(QPen)
• drawRect(int x, int y, int width, int height);
• drawLine
• drawPath(const QPainterPath &path) //current pen
• void QPainter::drawPolygon(const QPolygonF &points, Qt::FillRule fillRule = Qt::OddEvenFill)

void QPainter::drawEllipse(const QRectF &rectangle)

• save 保存当前painter状态

• restore 恢复

• setRenderHint(QPainter::RenderHint hint, bool on = true)
  设置绘画风格
  比如

painter->setRenderHint(QPainter::Antialiasing);
//带有边缘

void QPainter::fillRect(const QRectF]&rectangle, const QBrush&brush)
Fills the given rectangle with the brush specified.

Alternatively, you can specify a QColor instead of a QBrush; the QBrush constructor (taking a QColor argument) will automatically create a solid pattern brush.

相应有 fillPath等等

QBrush类

刷子,可以是纹理/颜色
style设置绘制的方式

QPen类

  pen.setStyle(Qt::DashDotLine);
  pen.setWidth(3);
  pen.setBrush(Qt::green);
  pen.setCapStyle(Qt::RoundCap);
  pen.setJoinStyle(Qt::RoundJoin);
  painter.setPen(pen)

QPainterPath类

• addRect等等

• clear

• boundingRect

• capacity vs length

• connectPath(&path)

• contains(QPoint/QRect/QPainterPath)

• 对应的intersect(相交),而contain是包含(区域)

• lineTo

• cubicTo 画线

0 moveTo
Moves the current position to (x, y) and starts a new subpath, implicitly closing the previous path.

游戏场景

QGraphicsItem类

• setPos(x, y);

• setData(int key, const QVariant &value);
  使用：serData(GD_Type, GO_Food);

• QRectF QGraphicsItem::boundingRect() const;
  自定义，原虚函数
  返回Item的边界
  例子：return QRectF(-TILE_SIZE, -TILE_SIZE, TILE_SIZE * 2, TILE_SIZE * 2 );

• （pure virtual） void QGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
  原虚函数，被QGraphicsView调用
  例子：

painter->save();
painter->setRenderHint(QPainter::Antialiasing);
painter->fillPath(shape(), Qt::red);
painter->restore();

• (virtual) QPainterPath shape()const
  例子:

QPainterPath p;
p.addEllipse(QPointF(TILE_SIZE / 2, TILE_SIZE / 2), FOOD_RADIUS, FOOD_RADIUS);
    return p;

• QPointF mapFromScene(const QPointF &point) const
  将Scene坐标系中的坐标映射到本Item坐标系中的点坐标

• void QGraphicsItem::advance(int phase)
  phase = 0 预更新
  phase = 1 更新
  用于更新Item相关逻辑

void Snake::advance(int step)
{
    if (!step) {
        return;
    }
    if (tickCounter++ % speed != 0) {
        return;
    }
    if (moveDirection == NoMove) {
        return;
    }
    if (growing > 0) {
		QPointF tailPoint = head;
        tail << tailPoint;
        growing -= 1;
    } else {
        tail.removeFirst();
        tail << head;
    }
    switch (moveDirection) {
        case MoveLeft:
            moveLeft();
            break;
        case MoveRight:
            moveRight();
            break;
        case MoveUp:
            moveUp();
            break;
        case MoveDown:
            moveDown();
            break;
    }
    setPos(head);
    handleCollisions();
}

• void QGraphicsItem::setPos(const QPointF &pos)
  Sets the position of the item to pos, which is in parent coordinates.

• 碰撞检测

QList<QGraphicsItem*> QGraphicsItem::collidingItems(Qt::ItemSelectionMode mode = Qt::IntersectsItemShape) const

可用之前设置的data判断与哪个物体的碰撞

QGraphicsScene类

//用于图形存放

• QGraphicsScene(QObject* parent = nullptr);
  构造函数可用：
  …scene(new QGraphicsScene(this));

• setSceneRect(x, y, w, h);//设置scene的位置
  //使用实例：scene->setSceneRect(-100, -100, 200, 200);

• void addItem(QGraphicsItem *item);
  void removeItem(QGraphicsItem *item);

• void QObject::installEventFilter(QObject *filterObj);
  //设置事件过滤器, filterObj会拦截并处理this的实践
  例子: scene.installEventFilter(this);

• (virtual)
  bool QObject::eventFilter(QObject *object, QEvent *event)
  实现拦截处理函数
  例子

if (event->type() == QEvent::KeyPress) {
    handleKeyPressed((QKeyEvent *)event); //自定义的按键处理函数
    return true;//返回已处理
} else {
    return QObject::eventFilter(object, event);
    //不处理
    }

• connect(&timer, SIGNAL(timeout()), &scene, SLOT(advance()));
  用于定时刷新界面

QGraphicsView类

• QGraphicsView(scene, this);

• void fitInView(QRect, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio);
  缩放视图矩阵并滚动滚动条，以确保场景矩形（rect）适应视口内

• setBackgroundBrush(QBrush(QPixmap)); //设置背景