QML - How to use QStringList as a model of ListView?

Question

I try to make TelnetClient.I use FileIO for read Telnet.There is no problem read or write and also create a string list but I need to show QStringList to ListView but I m getting error: "m_model is not defined".

I create QStringList:

QStringList FileIO::read() { if (m_source.isEmpty()) { emit error("source is empty"); return QStringList(); } QFile file(m_source); QString fileContent; QString line; QStringList list; if ( file.open(QIODevice::ReadWrite) ) { QTextStream t( &file ); line = t.readAll(); fileContent += line; list.append(line.split("\r\n")); foreach (QString item, list) { if (item[0].isNumber()) { list2.append(item); } } QQmlContext *ctxt; ctxt->setContextProperty("m_model", QVariant::fromValue(list2)); qDebug() << "\r\n\r\nlist2 =" << list2; line = t.readAll(); qDebug() << "SOURCE" << m_source; file.close(); } else { emit error("Unable to open the file"); return QStringList(); } return list2;

This can make a new QStringList successfully and also I assign my string list as a model; m_model.

ListView { id: listView1 x: 0 y: 0 model: m_model delegate: Rectangle{ Text {text: modelData } } }

and here is my ListView. When I try like this, I m getting error. How can I solve this problem. If I can use "list2" in main.cpp I can solve the problem but I don't know how can I use it in main.cpp because it exist in another class.

Thank you!

QQmlContext *ctxt; ctxt->setContextProperty("m_model", QVariant::fromValue(list2)); You even doesn't create ctxt object. The program should crash at this step. Despite the fact that you have no qml engine no context at all. This link can help you too. — folibis
– folibis, Commented Aug 5, 2016 at 17:22

Francisco Hernandez · Accepted Answer · 2016-10-10 04:29:44Z

You can try to set the context property with an instance of the class. That way, you can instantiate the class in main, and then pass it's address to set the context property. If the data of the model is subject to change while the program is running, I would suggest implementing the QStringList as a Q_Property.

//main.cpp FileIO fileIO; QQmlApplicationEngine engine; QQmlContext* ctx = engine.rootContext(); ctx->setContextProperty("fileio", &fileIO); engine.load(/* Path to your qml */); //qml ListView { id: listView1 x: 0 y: 0 model: fileio.m_model delegate: Rectangle{ Text {text: modelData } } }

tanius · Accepted Answer · 2020-07-10 11:01:46Z

To elaborate on Francisco's answer: if the data of the model is subject to change while the program is running, it is indeed the cleanest solution to implement the QStringList as a Q_PROPERTY, because that will send signals to QML objects when the model data changes. A good example is here.

According to the Qt Manual there is also another option:

Note: There is no way for the view to know that the contents of a QStringList have changed. If the QStringList changes, it will be necessary to reset the model by calling QQmlContext::setContextProperty() again.

An (untested) example of this technique is demonstrated below:

main.cpp:

QStringList updateStringList() { // Your code from "I create QStringList" goes here. } QStringList myStringList = updateStringList(); QQmlApplicationEngine engine; QQmlContext* ctx = engine.rootContext(); ctx->setContextProperty("m_model", &myStringList); engine.load("ListView.qml"); // ... more code ... myStringList = updateStringList(); ctx->setContextProperty("m_model", &myStringList);

ListView.qml:

ListView { id: listView1 x: 0 y: 0 model: fileio.m_model delegate: Rectangle{ Text {text: modelData } } }

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