当QLabel中的文字过长，在最后面显示省略号 

QString newStrMsg = "1234567890abcdefghijklmnopqrstuvwxyz";

QFontMetrics fontWidth(ui->noteValueLabel->font());    //得到每个字符的宽度
QString elideNote = fontWidth.elidedText(newStrMsg, Qt::ElideRight, 150);    //最大宽度150像素

ui->noteValueLabel->setText(elideNote);
ui->noteValueLabel->setToolTip(newStrMsg);

寻找文件夹中所有的某格式文件

bool scanData(const QDir& fromDir, const QStringList& filters = { "*.obj" });

bool QtTest::scanData(const QDir& fromDir, const QStringList& filters)
{
	QFileInfoList fileInfoList = fromDir.entryInfoList(filters, QDir::AllDirs | QDir::Files);
	foreach(QFileInfo fileInfo, fileInfoList)
	{
		if (fileInfo.fileName() == "." || fileInfo.fileName() == "..")
			continue;
		if (fileInfo.isDir())
		{
			if (!scanData(fileInfo.filePath(), filters))
				return false;
		}
		else
		{
			filePathList.append(fileInfo.absoluteFilePath());
		}
	}
	return true;
}

QPushButton设置菜单后取消右下角下拉三角形

m_pushButton->setStyleSheet("QPushButton::menu-indicator{image:none;}");

在qss中使用变量

QString color = "#00FF00";
QString styleSheet = "QLabel { background-color: %1;}";
ui.label->setStyleSheet(styleSheet.arg(color));

相对路径和绝对路径的转换

// 相对路径转绝对路径
QString relativePath = "./Test/test.txt"
QDir dir;
QString path = dir.absoluteFilePath(relativePath);

// 绝对路径转相对路径
QString absolutePath = "/home/wangjun/Test/test.txt"
QDir dir;
QString path = dir.relativeFilePath(abslutePath);

获取文件路径中的各类名字

// 绝对路径
QFileInfo fi("c:/temp/foo"); => fi.absoluteFilePath() => "C:/temp/foo"

// 文件名
QFileInfo fi("/tmp/archive.tar.gz");
QString base = fi.baseName();  // base = "archive"

// 文件名带半后缀
QFileInfo fi("/tmp/archive.tar.gz");
QString base = fi.completeBaseName();  // base = "archive.tar"

// 后缀名
QFileInfo fi("/tmp/archive.tar.gz");
QString ext = fi.suffix();  // ext = "gz"

// 完整后缀名
QFileInfo fi("/tmp/archive.tar.gz");
QString ext = fi.completeSuffix();  // ext = "tar.gz"

// 文件名带后缀
QFileInfo fi("/tmp/archive.tar.gz");
QString name = fi.fileName();                // name = "archive.tar.gz"、

QPushButton/QToolButton设置选中状态

思路：为Button设置Icon为具体图标，设置border-image为选中状态的边框图

// QPushButton类似
auto btn_1 = new QToolButton(this);
btn_1->setFixedSize(QSize(30, 30));
btn_1->setIcon(QIcon(":/img.png"));
btn_1->setStyleSheet("QToolButton{ border-image: url(:/test.png); }");
btn_1->setCheckable(true);
btn_1->setChecked(true);
this->layout()->addWidget(btn_1);

connect(btn_1, &QToolButton::clicked, this, [=]()
{
	if (btn_1->isChecked())
	{
		btn_1->setStyleSheet("QToolButton{ border: none; }");
	}
	else
		btn_1->setStyleSheet("QToolButton{ border-image: url(:/test.png); }");
});

QPushButton/QToolButton设置互斥

auto btn1 = new QPushButton();
auto btn2 = new QPushButton();
QButtonGroup* buttonGround = new QButtonGroup();
buttonGrounp->addButton(btn1);
buttonGrounp->addButton(btn2);
buttonGrounp->setExclusive(true);

QButtonGroup不选中任何按钮

QButtonGroup中默认必须有一个被选中，且无法取消其选中状态Qt官方描述如下：In an exclusive group, the user cannot uncheck the currently checked button by clicking on it; instead, another button in the group must be clicked to set the new checked button for that group。参照stackoverflow上的问答，可以自定义QToollButton解决此问题，链接如下：https://stackoverflow.com/questions/15177771/alternative-to-qbuttongroup-that-allows-no-selection

class CustomButton : public QToolButton
{
    Q_OBJECT

  public:
    CustomButton (QWidget* apo_parent = 0, const char* as_name = 0);
    virtual ~CustomButton ();

  protected:
    virtual void mousePressEvent(QMouseEvent* a_Event);
};


void CustomButton ::mousePressEvent(QMouseEvent* a_Event)
{
  if(group() && isToggleButton())
  {
    CustomButton* selectedButton(dynamic_cast<CustomButton*>(group()->selected()));
    if(selectedButton)
    {
      if(selectedButton->name() == name())
      {
        group()->setExclusive(false);
        toggle();
        group()->setExclusive(true);
        return;
      }
    }
  }
  QToolButton::mousePressEvent(a_Event);
}

将控件放入布局中的指定位置

 auto lbl_1 = new QLabel("Test", this);
 dynamic_cast<QVBoxLayout*>(this->layout())->insertWidget(1, lbl_1);

调用系统默认程序打开某文件

QDesktopServices::openUrl(QUrl("C://Users//wangjun//Desktop//qt5_cadaques.pdf"));

设置QSlider不可移动

slider.setEnabled(false);

QTimer和QThread

// 在构造函数中
thread = new QThread(this);
thread->start();
 
QTimer *timer = new QTimer(0);
timer->setInterval(100);
connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()), Qt::DirectConnection);
timer->start();
timer->moveToThread(thread);

// 在析构函数中
thread->quit();
if(!t->wait(3000))        // Wait until it actually has terminated (max. 3 sec)
{
    thread->terminate();  // Thread didn't exit in time, probably deadlocked, terminate it!
    thread->wait();       // We have to wait again here!
}

获取当前程序中的模态窗口

QApplication::activeModalWidget

在构造函数中退出程序

1.exit（-1）

2.QTimer::singleShot(0, qApp, SLOT(quit()))

判断鼠标是否在某一控件上

if(btn->geometry().contains(this->mapFromGlobal(QCursor::pos())))

枚举与字符串的相互转换

class QtTest : public QWidget
{
    Q_OBJECT
public:
	QtTest(QWidget *parent = 0);
	enum Color { RED, GREEN, BLUE };
	Q_ENUM(Color)


private:
    Ui::QtTest10Class ui;
};


QtTest10::QtTest10(QWidget *parent)
    : QWidget(parent)
{
    ui.setupUi(this);

	QMetaEnum metaColor = QMetaEnum::fromType<Color>();
	qDebug() << metaColor.valueToKey(BLUE);
	qDebug() << metaColor.keyToValue("BLUE", &isOk) << isOk;
	qDebug() << metaColor.keyToValue("BLUE", &isOk) << isOk;
}

QListWidget设置item可编辑

item->setFlags(item->flags() | Qt::ItemIsEditable);

QWidget像QDialog一样阻塞窗口

connect(ui->pushButton, &QPushButton::clicked, this, [=]()
{
    QWidget widget;
	widget.setAttribute(Qt::WA_ShowModal, true);
	widget.show();
	QEventLoop loop;
	loop.exec();
}

打印当前Qt版本

qDebug() << QT_VERSION_STR;