So I'm new to Qt and I'm trying to improve my C++ skills, so I decided to start a project where I can search items in a QStringList using a textfield. I got the search function working and I was able to move the result of the search into another QStringList, where I can use it to display to the user in a function that is declared as a "public slot".
The main Idea is that the list will auto update as soon as the user enters a character into the textfield, which it already does. So I managed to get the resulted list into the Slot function to be able to display a different list every time and character gets typed in the textfield.
In the function where I pass in the list of search results, I am trying to use this
m_context->setContextProperty("resultModel",QVariant::fromValue(m_resultList));
where resultModel is the name of my model in QML and m_resultList is where the results of the search are being stored, to display the list in the ListView. My program compiles but it crashes after I run it.
So, my true question is: Is there any way that I can display a C++ QStringList not in the main.cpp into a QML ListView?
The reason why I'm asking for it to not be in the main is because I tried to use that same line above in the main.cpp with a hard coded QStringList and the list was able to display, so there must be an issue with it not being in the main. Also because I would not be able to use the slot function in SearchClass to auto update.
main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QDebug>
#include "searchclass.h"
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
qmlRegisterType<SearchClass>("b9c.backend", 1, 0, "BackEnd");
QQmlApplicationEngine engine;
SearchClass obj;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
QQmlContext *context = engine.rootContext();
obj.getContext(context);
//the line below works if provided with a qstringlist
//context->setContextProperty("resultModel", QVariant::fromValue(resultList));
return app.exec();
}
SearchClass.h
#ifndef SEARCHCLASS_H
#define SEARCHCLASS_H
#include <QObject>
#include <QQmlContext>
class SearchClass : public QObject
{
Q_OBJECT
Q_PROPERTY(QString userSearch READ userSearch WRITE setUserSearch NOTIFY userSearchChanged)
public:
SearchClass(QObject *parent = 0);
QStringList resultList;
QString userSearch();
void setUserSearch(QString &userSearch);
void getFilenameAndInput(QString inputString);
QString CompareInputAndFilename(QString inputString, QString filename);
QStringList getFileName();
//get context
void getContext(QQmlContext *context);
signals:
void userSearchChanged();
public slots:
void setUserSearch();
private:
QStringList m_resultList;
QString m_userSearch;
QQmlContext* m_context;
};
#endif // SEARCHCLASS_H
SearchClass.cpp
#include "searchclass.h"
#include <QDebug>
#include <QQmlContext>
#include <QGuiApplication>
#include <QQmlApplicationEngine>
SearchClass::SearchClass(QObject *parent) : QObject(parent)
{
connect(this, SIGNAL(userSearchChanged()), this, SLOT(setUserSearch()));
}
//the result should be displayed in this SLOT when ever the user types in a character into the textfield
void SearchClass::setUserSearch(){
qDebug() << "SLOT: " << m_resultList;
//The line below makes the program crash. It works when implemented in the main.cpp
// m_context->setContextProperty("resultModel", QVariant::fromValue(m_resultList));
}
QString SearchClass::userSearch()
{
return m_userSearch;
}
void SearchClass::setUserSearch(QString &userSearch)
{
if (userSearch == m_userSearch)
return;
m_userSearch = userSearch;
qDebug() << "Input: " <<m_userSearch;
getFilenameAndInput(m_userSearch);
emit userSearchChanged();
}
QStringList SearchClass::getFileName(){
//Returns the items that will be searched for...
}
void SearchClass::getFilenameAndInput(QString inputString){
//Puts the search results into class variable m_resultList...
m_resultList = resultList;
}
QString SearchClass::CompareInputAndFilename(QString inputString, QString filename){
//Search processing...
}
//gets context to use setProperty in the above signal, but it crashes
void SearchClass::getContext(QQmlContext *context){
m_context = context;
}
main.qml
import QtQuick 2.6
import QtQuick.Controls 2.0
import b9c.backend 1.0
import QtQuick.Window 2.2
ApplicationWindow {
id: root
width: 300
height: 480
visible: true
BackEnd { id: backend }
TextField {
id: txtfield
text: backend.userSearch
placeholderText: qsTr("Search...")
width: parent.width
onTextChanged: backend.userSearch = text
}
ListView {
id:view
height: parent.height
width: parent.width
y: 5 + txtfield.height
model: resultModel
delegate: Rectangle {
border.color: "lightblue"
height: 25
width: parent.width
Text {
anchors.centerIn: parent
text: modelData
}
}
}
}
You are doing it wrong. In every possible way. You even name getContext() the function that actually sets the context.
m_resultList is never set to anything in that code you have provided. So there is no way to tell you why your application is crashing, because the actual data is a mystery.
You also have a QObject derived class - your SearchClass. So you should expose that as a context property, and then have the string list interfaced to QML by being implemented as a Q_PROPERTY of SearchClass.
Here is a simple example:
// the equivalent of your SearchClass
class Test : public QObject {
Q_OBJECT
Q_PROPERTY(QStringList model MEMBER m_model NOTIFY modelChanged)
QStringList m_model;
public slots:
void setModel(QString m) {
m_model = m.split(" ");
modelChanged();
}
signals:
void modelChanged();
};
// in main.cpp
Test t;
engine.rootContext()->setContextProperty("Test", &t);
// in main.qml
Column {
TextField {
onTextChanged: Test.setModel(text)
}
ListView {
width: 200; height: 300
spacing: 5
model: Test.model
delegate: Rectangle {
height: 25
width: 200
color: "lightgray"
Text { text: modelData; anchors.centerIn: parent }
}
}
}
As you type the text string is sent to Test::setModel(), which then splits it into space separated tokens and sets the QStringList, which is used as a model source for the list view.