QT5的一些常用函数（菜单，工具条，label，QMessageBox，定时器）

最近用QT做UI确实感觉漂亮和方便，常会用到一些小技巧，总结一下，方便以后的快速使用。
1.添加菜单
#include <QMenu>

QMenu* menu_file = new QMenu("File");
menu_file->addAction("Start",this,SLOT(openCamera()));
menu_file->addAction("Stop");
menu_file->addAction("Quit");

QMenu* menu_edit = new QMenu("Edit");
menu_edit->addAction("Show feature points",this,SLOT(show_features()));
menu_edit->addAction("Save face image",this,SLOT(SaveFaceDetected()));

QMenu* menu_help = new QMenu("Help");
menu_help->addAction("Technical Support");
menu_help->addAction("Contact us");

ui->menuBar->addMenu(menu_file);
ui->menuBar->addMenu(menu_edit);

ui->menuBar->addMenu(menu_help);

2.添加工具条
#include <QToolBar>
#include <QAction>

QAction* new_Action = new QAction(QIcon(":/icons/big_icons/new.png") ,tr("&Add New..."),this);
new_Action->setStatusTip(tr("Add a new tool !"));
connect(new_Action,&QAction::triggered,this,MainWindow::add_new_tool);

ui->mainToolBar->addAction(new_Action);
3.开定时器
#include <QTimer>

QTimer* show_timer = new QTimer();
connect(show_timer,SIGNAL(timeout()),this,SLOT(updateTimer()));
show_timer->start(1000);
//需要定义和实现槽函数 updateTimer()
private slots:
void updateTimer();
4.label设置常规属性（label显示图像）
#include <QLabel>
Mat person = Mat::zeros(200,150,CV_8UC3);
cv::cvtColor(person,person,CV_BGR2RGB);
img = QImage((const unsigned char*)(person.data),person.cols,person.rows,QImage::Format_RGB888)

ui->label->setFrameShape(QFrame::Box);//设置边框
ui->label->setStyleSheet("border: 2px solid #00ff00");//边框颜色
ui->label->setScaledContents(true);
ui->label->setPixmap(QPixmap::fromImage(img));
QString name = "姓名： ";
ui->label->setText(name);

//设置字号
QFont name_ft;
name_ft.setPointSize(10);
ui->label->setFont(name_ft);

//设置颜色
QPalette pa;
pa.setColor(QPalette::WindowText,Qt::blue);
ui->label->setPalette(pa);解决显示图像扭曲的问题：void MyDisplayWidget::show_image(Mat im)
{
if(im.empty())
return;
cv::cvtColor(im, im, CV_BGR2RGB);
qt_image = QImage((const unsigned char*)im.data,
im.cols,
im.rows,
im.cols*im.channels(),
QImage::Format_RGB888);

im_label->setPixmap(QPixmap::fromImage(qt_image));
}

5.QMessageBox的使用
#include <QMessageBox>
QMessageBox::information(this,
tr("error"),
tr("Open camera 0 failed！"));