我想在两个QWidget实例之间共享一个字符串。
在main.cpp中,实例化了两个对象,如下所示:
#include "dialog.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Dialog w1,w2; //Derived from QWidget
w1.show();
w2.show();
return a.exec();
}
答案 0 :(得分:2)
我将介绍SharedState类:
// shared_state.h
#ifndef SHARED_STATE_HPP
#define SHARED_STATE_HPP
#include <QObject>
class SharedState : public QObject
{
Q_OBJECT
public:
SharedState(QString initialValue = "")
: currentValue(initialValue)
{}
QString getCurrentValue()
{
return currentValue;
}
public slots:
void setValue(QString newValue)
{
if(currentValue != newValue)
{
currentValue = newValue;
emit valueChanged(currentValue);
}
}
signals:
void valueChanged(QString);
private:
QString currentValue;
};
#endif // SHARED_STATE_HPP
现在我将在Dialog的构造函数中提供对SharedState的引用,
// dialog.h
#ifndef DIALOG_H
#define DIALOG_H
#include <QWidget>
#include "shared_state.h"
namespace Ui {
class Dialog;
}
class Dialog : public QWidget
{
Q_OBJECT
public:
explicit Dialog(SharedState& state, QWidget *parent = 0);
~Dialog();
private slots:
void handleTextEdited(const QString&);
public slots:
void handleInternalStateChanged(QString);
private:
Ui::Dialog *ui;
SharedState& state;
};
#endif // DIALOG_H
您可能已经注意到我添加了两个插槽,一个用于处理手动编辑文本时的情况,另一个用于处理共享状态将告知我们已过期的插槽。
现在在Dialog的构造函数中,我必须将初始值设置为textEdit,并将信号连接到插槽。
// dialog.cpp
#include "dialog.h"
#include "ui_dialog.h"
Dialog::Dialog(SharedState& state, QWidget *parent) :
QWidget(parent),
ui(new Ui::Dialog),
state(state)
{
ui->setupUi(this);
ui->textEdit->setText(state.getCurrentValue());
QObject::connect(ui->textEdit, SIGNAL(textEdited(QString)),
this, SLOT(handleTextEdited(QString)));
QObject::connect(&state, SIGNAL(valueChanged(QString)),
this, SLOT(handleInternalStateChanged(QString)));
}
Dialog::~Dialog()
{
delete ui;
}
void Dialog::handleTextEdited(const QString& newText)
{
state.setValue(newText);
}
void Dialog::handleInternalStateChanged(QString newState)
{
ui->textEdit->setText(newState);
}
现在main
功能的变化:
// main.cpp
#include "dialog.h"
#include "shared_state.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
SharedState state("Initial Value");
Dialog w1(state), w2(state);
w1.show();
w2.show();
return a.exec();
}