我有一个从表中获取值的组合框。我使用：
获取组合框对象QObject * object=engine->rootObjects().at(0)->findChild<QObject* >("comboobjectname");
现在，如何从组合框列表中设置一个值并使用C ++在GUI上设置它？
答案 0 :(得分：2)
我总是建议：如果你有一个模型，请使用模型更新你的GUI。
我不知道你的整个项目，但是如果你有C ++中的模型，你应该有一个类，可以添加，删除和获取数据。
在这个例子中，我将向您展示一个非常简单的模型Animal，它有两个值：类型和大小。
<强> animal.h
#ifndef ANIMAL_H
#define ANIMAL_H
#include <QString>
class Animal
{
public:
Animal(const QString &type, const QString &size);
QString type() const;
QString size() const;
private:
QString m_type;
QString m_size;
};
#endif // ANIMAL_H
<强> animal.cpp
#include "animal.h"
Animal::Animal(const QString &type, const QString &size)
: m_type(type), m_size(size)
{
}
QString Animal::type() const
{
return m_type;
}
QString Animal::size() const
{
return m_size;
}
<强> animalmodel.h
#ifndef ANIMALMODEL_H
#define ANIMALMODEL_H
#include <QAbstractListModel>
#include <QStringList>
#include "animal.h"
class AnimalModel : public QAbstractListModel
{
Q_OBJECT
public:
enum AnimalRoles {
TypeRole = Qt::UserRole + 1,
SizeRole
};
AnimalModel(QObject *parent = 0);
Q_INVOKABLE void addAnimal(const QString &type, const QString &size);
void addAnimal(const Animal &animal);
Q_INVOKABLE void removeAnimal(int row);
int rowCount(const QModelIndex & parent = QModelIndex()) const;
QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
protected:
QHash<int, QByteArray> roleNames() const;
private:
QList<Animal> m_animals;
};
#endif // ANIMALMODEL_H
<强> animalmodel.cpp
#include "animalmodel.h"
#include <QDebug>
#include <QListIterator>
AnimalModel::AnimalModel(QObject *parent)
: QAbstractListModel(parent)
{
}
void AnimalModel::addAnimal(const QString &type, const QString &size)
{
addAnimal(Animal(type, size));
}
void AnimalModel::addAnimal(const Animal &animal)
{
beginInsertRows(QModelIndex(), rowCount(), rowCount());
m_animals << animal;
endInsertRows();
}
void AnimalModel::removeAnimal(int row)
{
beginRemoveRows(QModelIndex(), row, row);
m_animals.removeAt(row);
removeRow(row, QModelIndex());
endRemoveRows();
}
int AnimalModel::rowCount(const QModelIndex & parent) const {
Q_UNUSED(parent);
return m_animals.count();
}
QVariant AnimalModel::data(const QModelIndex & index, int role) const {
if (index.row() < 0 || index.row() >= m_animals.count())
return QVariant();
const Animal &animal = m_animals[index.row()];
if (role == TypeRole)
return animal.type();
else if (role == SizeRole)
return animal.size();
return QVariant();
}
QHash<int, QByteArray> AnimalModel::roleNames() const {
QHash<int, QByteArray> roles;
roles[TypeRole] = "type";
roles[SizeRole] = "size";
return roles;
}
感谢此模型，我们可以在QML中使用它来显示，例如TableView和ComboBox：
import QtQuick 2.0
import QtQuick.Controls 1.4
import QtQuick.Layouts 1.1
import QtQuick.Controls.Styles 1.4
ApplicationWindow {
id: window
visible: true
width: 640
height: 480
title: qsTr("")
toolBar: ToolBar {
id: toolbar
width: parent.width
style: ToolBarStyle {
padding {
left: 20
right: 20
top: 15
bottom: 15
}
background: Rectangle {
implicitWidth: 100
implicitHeight: 40
border.color: "#999"
gradient: Gradient {
GradientStop { position: 0 ; color: "#fff" }
GradientStop { position: 1 ; color: "#aaa" }
}
}
}
ColumnLayout{
spacing: 2
RowLayout {
Button {
id: addButton
anchors.verticalCenter: parent.verticalCenter
text: "Add item"
onClicked: {
if (typeBox.text || sizeBox.text) {
myModel.addAnimal(typeBox.text, sizeBox.text)
}
}
}
TextField {
id: typeBox
placeholderText: "type"
anchors.verticalCenter: parent.verticalCenter
anchors.left: addButton.right
anchors.leftMargin: 5
}
TextField {
id: sizeBox
placeholderText: "size"
anchors.verticalCenter: parent.verticalCenter
anchors.left: typeBox.right
anchors.leftMargin: 5
}
}
RowLayout {
Button {
id: deleteButton
anchors.verticalCenter: parent.verticalCenter
text: "Delete item"
onClicked: {
if(tableView.currentRow != -1)
{
myModel.removeAnimal(tableView.currentRow)
}
}
}
}
ColumnLayout{
spacing: 2
RowLayout {
ComboBox {
id: myCombobox
currentIndex: 2
model: myModel
textRole : "type"
}
Button {
id: printvaluesButton
anchors.verticalCenter: parent.verticalCenter
text: "Print values"
onClicked: {
console.debug(myCombobox.currentIndex)
comboboxManagement.printValues(myModel,
myModel.index(myCombobox.currentIndex, 0))
}
}
}
}
}
}
TableView {
id: tableView
frameVisible: false
sortIndicatorVisible: true
anchors.fill: parent
Layout.minimumWidth: 400
Layout.minimumHeight: 240
Layout.preferredWidth: 600
Layout.preferredHeight: 400
TableViewColumn {
role: "type"
title: "Type"
width: 100
}
TableViewColumn {
role: "size"
title: "Size"
width: 200
}
model: myModel
}
}
如您所见，我们有一些按钮来添加和删除项目。单击按钮后，TableView和ComboBox都会更新。
在我们的ComboBox的特定情况下，我们有一个C ++类来打印所选元素。是否有这样的课程来执行这些任务取决于您并且取决于您的要求。
<强> comboboxmanagement.h
#ifndef COMBOBOXMANAGEMENT_H
#define COMBOBOXMANAGEMENT_H
#include <QObject>
#include <QDebug>
#include "animalmodel.h"
class ComboboxManagement : public QObject
{
Q_OBJECT
public:
explicit ComboboxManagement(QObject *parent = 0);
Q_INVOKABLE bool printValues(AnimalModel* model,
const QModelIndex &modelIndex);
};
#endif // COMBOBOXMANAGEMENT_H
<强> comboboxmanagement.cpp
#include "comboboxmanagement.h"
ComboboxManagement::ComboboxManagement(QObject *parent) : QObject(parent)
{
}
bool ComboboxManagement::printValues(AnimalModel* model,
const QModelIndex &modelIndex) {
qDebug() << model->data(modelIndex, AnimalModel::TypeRole);
return true;
}
最后，main.cpp
#include "animalmodel.h"
#include "comboboxmanagement.h"
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <qqmlcontext.h>
#include <qqml.h>
#include <QtQuick/qquickitem.h>
#include <QtQuick/qquickview.h>
int main(int argc, char ** argv)
{
QGuiApplication app(argc, argv);
AnimalModel model;
model.addAnimal(Animal("Wolf", "Medium"));
model.addAnimal(Animal("Polar bear", "Large"));
model.addAnimal(Animal("Quoll", "Small"));
ComboboxManagement comboboxManagement;
QQmlApplicationEngine engine;
QQmlContext *ctxt = engine.rootContext();
ctxt->setContextProperty("myModel", &model);
ctxt->setContextProperty("comboboxManagement", &comboboxManagement);
engine.load(QUrl(QStringLiteral("qrc:/view.qml")));
return app.exec();
}