qlist

I am trying to display a large amount of columnar records in a scrollable view using Qt (5.1). The number of rows I would like to be able to browse can vary from 100 million to 1 Billion, say. The QTableWidget with a custom model works a few million rows, but the QTableWidget allocates data for each row because you can re-size the rows height, and so it must store data for this, which can use megabytes or even gigabytes of memory with 100M rows. I do not require the re-sizeable rows functionality just a multi-column list would be ideal, but QTreeCtrl doesnt seem to work with many rows, and

Reimplemented Protected Functions（重新实现的受保护的方法） 在我测试关于drag and drop (拖放事件)的时候，我发现同样给QFrame和QListWidget添加三个Qlabel组件，QFrame和QListWidget对于鼠标响应事件的处理机制是不同的，后面翻看Qt源代码之后发现： QFrame直接继承于QWidget，对于event(QEvent* e)实现了一次重载。 而QListWidget通过多次继承之后继承于QWidget，在此期间event(QEvent* e)实现了多次重载，具体是做什么没有去细看，可以想象QFrame和QListWidget对于事件的处理是有差别的。 自己做的测试是 ：把三个QLabel分别放进QFrame和QListWidget之后对QLabel使用鼠标点击，QFrame和QListWidget都重新实现了mousePressEvent(QMousePressEvent* event),但是只有QFrame对鼠标按下事件做出响应，QListWidget没有对鼠标按下事件做出响应。 来源： https://blog.csdn.net/n__o_more/article/details/100980329

I want to save a QList<int> to my QSettings without looping through it. I know that I could use writeArray() and a loop to save all items or to write the QList to a QByteArray and save this but then it is not human readable in my INI file.. Currently I am using the following to transform my QList<int> to QList<QVariant> : QList<QVariant> variantList; //Temp is the QList<int> for (int i = 0; i < temp.size(); i++) variantList.append(temp.at(i)); And to save this QList<Variant> to my Settings I use the following code: QVariant list; list.setValue(variantList); //saveSession is my QSettings object

Qt提供了多种容器类，这些容器可以用于存储指定类型的数据项，并且可以实现对字符串列表的添加，存储，删除等操作。 容器类是基础模板的类，如常用的容器类 QList <T> ,T是一个具体的类型，可以是int，float等简单类型，也可以是QString,QDate等类，但不可以是QObject或任何其子类。T必须是一个可赋值的类型。 例如用 QList <T> 定义一个字符串列表的容器，其定义方法是： QList <QString> strList; 这样定义了一个QList容器类的变量strList，它的数据项是QString,所以strList可以用于处理字符串列表，例如： strList.append("one"); strList.append("two"); strList.append("three"); QString str = strList[0]; //str = "one" Qt的容器类大致分为 顺序容器 和 关联容器 。 顺序容器类 Qt的顺序容器类有QList,QLinkedList,QVector,QStack和QQueue。 QList QList是最常用的容器类，虽然它是以数组列表的形式实现的，但是在其前后添加数据非常快，QList以下标索引的方式对数据项进行访问。 QList用于添加，插入，替换，移动，删除数据项的函数有：insert()

If I've got a list of things in C++, how do I expose that to QML (in Qt5 / QtQuick 2)? It seems like QML can only understand QObject -derived classes, which is an issue because QObject s can't be put in a QList or copied. How do I do this: struct Thing { int size; QString name; }; class ThingManager : public QObject { Q_OBJECT // These macros support QtQuick, in case we one day want to use it to make a slick // interface (when QML desktop components are released). Q_PROPERTY(QList<Thing> things READ things NOTIFY thingssChanged) public: // ... QList<Thing> things() const; // ... }; So that I

The Qt container classes QList<T> , QVector<T> etc. require their element types to be copyable. Since C++11, the STL containers require their element type to be copyable or movable only. Why do the Qt containers not support move-only element types? Qt bug #54685 has explicit confirmation from Qt developers that move-only types are not (and will never be) supported because of Qt containers' principle of implicit sharing. When you copy one Qt container to another, you're not doing a deep copy—the containers share their contents internally. Only when a modifying function is called on a container

I have a graphical application written in Qt for embedded linux. Part of this application is to update a display screen every 250 ms. However, after about 8-10 hours the application crashes with a "QList: Out of memory" error. I've isolated the function and the lines (in a sense) where it happens, but I have no idea why it happens since I'm not using QList. The only active lines of code in this function are at the end of this question. I realize that QList doesn't ever 'shrink' the memory it uses to hold items, but I'm not using QList anywhere in my code. I'm only calling 'setStyleSheet' to