MessageDialog - 从 C++ 更改文本但屏幕上没有更新

Question

我已经设法动态更改包含 MessageDialog 的 QML Item 中的几个属性。我可以读取新设置的属性，但它们不会在屏幕上更新 - 它仍然是可见的 QML 设置的文本。我什至手动发送了 textChanged() 信号（见下文）无济于事。

知道我错过了什么吗？这是我的做法：

"ErrorDialog.qml":

Item{
    id: baseItem
    property string text: "myText"
    property string title: "myTitle"
    signal acceptedSignal()
    onTextChanged: {
        errorDialogItem.text=baseItem.text
    }
    MessageDialog {
        id: errorDialogItem
        objectName: "errorDialogItem"
        text: baseItem.text
        title: baseItem.title
        onAccepted: {
            acceptedSignal()
        }
    Component.onCompleted: visible=true
}

现在 c++:

this->component = QSharedPointer<QQmlComponent>(new QQmlComponent(&this->engine));
QObject::connect(&engine, SIGNAL(quit()), QCoreApplication::instance(), SLOT(quit()));
component->loadUrl(QUrl(QStringLiteral("qrc:///main.qml")));

topLevel = QSharedPointer<QObject>(component->create());
window = qobject_cast<QQuickWindow *>(topLevel.data());

surfaceFormat = window->requestedFormat();
window->setFormat(surfaceFormat);
window->show(); 

QQmlComponent dialogComponent(&engine, QUrl(QStringLiteral("qrc:///ErrorDialog.qml")));
QObject *myObject = dialogComponent.create();
QQuickItem *item = qobject_cast<QQuickItem*>(myObject);

QQmlEngine::setObjectOwnership(item, QQmlEngine::CppOwnership);
qDebug()<<"title"<<item->property("title");
qDebug()<<"text"<<item->property("text");
QString newText="TEXT SET FROM C++";
qDebug()<<"setTextProp: "<<item->setProperty("text",newText);
//-> true
qDebug()<<"new text"<<item->property("text"); 
//-> correctly set!

属性已设置，但视觉上未更改。所以我获取了嵌入式 MessageDialog 本身：

QObject* dialogObject=item->findChild<QObject*>("errorDialogItem");
QQuickItem* dialogItem=reinterpret_cast<QQuickItem*>(dialogObject);

item->setFlag(QQuickItem::ItemHasContents,true);
dialogItem->setFlag(QQuickItem::ItemHasContents,true);

我正在尽我所能，更新屏幕上的文本：

dialogItem->polish();
item->polish();

int methodIndex=item->metaObject()->indexOfMethod("textChanged()"); 
QMetaMethod method = item->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(item,Qt::DirectConnection);
//-->true

methodIndex=item->metaObject()->indexOfMethod("update()"); 
method = item->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(item,Qt::DirectConnection);
//-->true

methodIndex=dialogItem->metaObject()->indexOfMethod("textChanged()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection);
//-->true   

methodIndex=dialogItem->metaObject()->indexOfMethod("windowGeometryChanged()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection);
//-->true

methodIndex=dialogItem->metaObject()->indexOfMethod("geometryChanged()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection);
//-->true

methodIndex=dialogItem->metaObject()->indexOfMethod("reset()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection);
//-->true

methodIndex=dialogItem->metaObject()->indexOfMethod("setVisible()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection,Q_ARG(bool,falseVar));
//-->false

methodIndex=dialogItem->metaObject()->indexOfMethod("setVisible()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection, Q_ARG(bool,trueVar));
//-->false

methodIndex=dialogItem->metaObject()->indexOfMethod("setText()"); 
method = dialogItem->metaObject()->method(methodIndex);
QString textStr = "a different text";
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection, Q_ARG(QString,textStr));
//-->false

methodIndex=dialogItem->metaObject()->indexOfMethod("polish()"); 
method = dialogItem->metaObject()->method(methodIndex);
qDebug()<<"invoke: "<<method.invoke(dialogItem,Qt::DirectConnection);
//-->false

Answer 1

感谢@BaCaRoZzo，在创建最小示例时我发现了问题所在。在打开 Dialog 之前属性更改绝对是强制性的，即处于关闭状态。如果我想更改已打开的 MessageDialog 中的内容，我必须关闭它，更改属性，然后再次打开它。更改属性然后关闭并重新打开（如 "redraw"）是不够的。参见

bool setItemProperty(QString role, T value)

在下面的 .h 文件中。

这是我的工作代码，非常感谢任何进一步的建议。注意："Controller" class 只是一些 class 提供了 GUI 的 QQmlApplicationEngine。

C++-Class header: MessageDialog.h

#ifndef MESSAGEDIALOG_H #define MESSAGEDIALOG_H #include <QObject> #include <QQuickItem> #include <QDialog> #include <QQmlApplicationEngine> #include "src/controller/controller.h" class MessageDialog : public QObject { Q_OBJECT public: enum StandardButton { Ok = 0x00000400, // An "OK" button with AcceptRole. Open = 0x00002000, // An "Open" button with AcceptRole. Save = 0x00000800, // A "Save" button with AcceptRole. Cancel = 0x00400000, // A "Cancel" button with RejectRole. Close = 0x00200000, // A "Close" button with RejectRole. Discard = 0x00800000, // A "Discard" button, DestructiveRole. Apply = 0x02000000, // An "Apply" button with ApplyRole. Reset = 0x04000000, // A "Reset" button with ResetRole. RestoreDefaults = 0x08000000,//"Restore Defaults", ResetRole. Help = 0x01000000, // A "Help" button with HelpRole. SaveAll = 0x00001000, // A "Save All" button with AcceptRole. Yes = 0x00004000, // A "Yes" button with YesRole. YesToAll = 0x00008000, // A "Yes to All" button with YesRole. No = 0x00010000, // A "No" button with NoRole. NoToAll = 0x00020000, // A "No to All" button with NoRole. Abort = 0x00040000, // An "Abort" button with RejectRole. Retry = 0x00080000, // A "Retry" button with AcceptRole. Ignore = 0x00100000, // An "Ignore" button with AcceptRole. NoButton = 0x00000000 // An invalid button. }; typedef QFlags<StandardButton> StandardButtons; enum ButtonRole { InvalidRole = -1, //button is invalid. AcceptRole = 0, //accepted (e.g. OK). RejectRole = 1, //rejected (e.g. Cancel). DestructiveRole = 2,//destructive change ActionRole = 3, //changes dialog. HelpRole = 4, //request help. YesRole = 5, //Yes"-like button. NoRole = 6, //"No"-like button. ApplyRole = 8, //applies current changes. ResetRole = 7 //resets the dialog to default values. }; enum Icon { NoIcon = 0, // the message box does not have any icon. Question = 4, // message is asking a question. Information = 1, // message is nothing out of the ordinary. Warning = 2, // message is a warning, but can be dealt with. Critical = 3 // message represents a critical problem. }; MessageDialog(Controller* controller, QString title=QString(), QString text=QString(), QString informativeText=QString(), QString detailedText=QString(), StandardButtons buttons=QFlags<StandardButton>()); ~MessageDialog(); void setText (const QString &text); void setInformativeText (const QString &text); void setDetailedText (const QString &text); void setTitle(const QString &title); bool open(); bool close(); void setStandardButtons(StandardButtons buttons); void addButton(StandardButton button); void setIcon(Icon icon); StandardButton clickedButton(); void setModality(Qt::WindowModality modality); int result(); StandardButton exec(); static void about(Controller* controller, const QString &title, const QString &text, const QString &informativeText="", const QString &detailedText=""); static StandardButton warning( Controller* controller, const QString &title, const QString &text, const QString &informativeText, const QString &detailedText, StandardButton button0 = NoButton, StandardButton button1 = NoButton, StandardButton button2 = NoButton, StandardButton button3 = NoButton); static MessageDialog::StandardButton information( Controller* controller, const QString &title, const QString &text, const QString &informativeText, const QString &detailedText, StandardButton button0 = NoButton, StandardButton button1 = NoButton, StandardButton button2 = NoButton, StandardButton button3 = NoButton); signals: void buttonClicked(StandardButton standardButton); void accepted(); void apply(); void discard(); void help(); void no(); void rejected(); void reset(); void yes(); public slots: protected: void initItem(Controller* controller); void connectQMLSignals(); bool invokeMethod(QString methodSignature); bool setStrings( const QString &title, const QString &text, const QString informativeText, const QString detailedText); template <typename T> bool setItemProperty(QString role, T value) { Q_ASSERT(m_item); bool wasOpen=m_isOpen; close(); bool success; success=m_item->setProperty(role.toLocal8Bit(),QVariant(value)); if(!success) qDebug()<<"setProperty("<<role<<","<<value<<") failed."; if (wasOpen) open(); return success; } QQmlApplicationEngine* m_engine; QQuickItem* m_item; bool m_isOpen; StandardButtons m_standardButtons; StandardButton m_result; }; #endif // MESSAGEDIALOG_H

C++-Class 实现：MessageDialog.cpp

#include "messagedialog.h" #include <QQuickItem> #include <QQmlApplicationEngine> MessageDialog::MessageDialog( Controller *controller, QString title, QString text, QString informativeText, QString detailedText, StandardButtons buttons) { Q_ASSERT(controller); this->initItem(controller); m_isOpen=false; m_result=MessageDialog::NoButton; this->setTitle(title); this->setText(text); this->setInformativeText(informativeText); this->setDetailedText(detailedText); this->setStandardButtons(buttons); this->connectQMLSignals(); } MessageDialog::~MessageDialog() { delete m_item; } void MessageDialog::setText(const QString &text) { setItemProperty("text",text); } void MessageDialog::setInformativeText(const QString &text) { setItemProperty("informativeText",text); } void MessageDialog::setDetailedText(const QString &text) { setItemProperty("detailedText",text); } void MessageDialog::setTitle(const QString &title) { setItemProperty("title",title); } void MessageDialog::setStandardButtons(StandardButtons buttons) { setItemProperty("standardButtons",buttons); m_standardButtons=buttons; } void MessageDialog::addButton(MessageDialog::StandardButton button) { m_standardButtons|=button; setItemProperty("standardButtons",m_standardButtons); } void MessageDialog::setIcon(MessageDialog::Icon icon) { setItemProperty("icon",icon); } MessageDialog::StandardButton MessageDialog::clickedButton() { int i=m_item->property("clickedButton").toInt(); return static_cast<MessageDialog::StandardButton>(i); } void MessageDialog::setModality(Qt::WindowModality modality) { setItemProperty("modality",modality); } int MessageDialog::result() { return this->clickedButton(); } MessageDialog::StandardButton MessageDialog::exec() { QEventLoop loop; connect(m_item, SIGNAL(accepted()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(apply()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(discard()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(help()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(no()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(rejected()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(reset()),& loop, SLOT(quit()),Qt::UniqueConnection); connect(m_item, SIGNAL(yes()),& loop, SLOT(quit()),Qt::UniqueConnection); invokeMethod("open()"); setModality(Qt::ApplicationModal); loop.exec(); return this->clickedButton(); } void MessageDialog::about( Controller *controller, const QString &title, const QString &text, const QString &informativeText, const QString &detailedText) { MessageDialog dialog(controller); dialog.setStrings(title,text,informativeText,detailedText); dialog.setIcon(MessageDialog::Information); dialog.setStandardButtons(Ok); dialog.exec(); } MessageDialog::StandardButton MessageDialog::warning( Controller *controller, const QString &title, const QString &text, const QString &informativeText, const QString &detailedText, MessageDialog::StandardButton button0, MessageDialog::StandardButton button1, MessageDialog::StandardButton button2, MessageDialog::StandardButton button3) { MessageDialog dialog(controller); dialog.setStrings(title,text,informativeText,detailedText); dialog.setIcon(MessageDialog::Warning); dialog.setStandardButtons( StandardButtons(button0|button1|button2|button3)); dialog.exec(); return dialog.clickedButton(); } MessageDialog::StandardButton MessageDialog::information( Controller *controller, const QString &title, const QString &text, const QString &informativeText, const QString &detailedText, MessageDialog::StandardButton button0, MessageDialog::StandardButton button1, MessageDialog::StandardButton button2, MessageDialog::StandardButton button3) { MessageDialog dialog(controller); dialog.setStrings(title,text,informativeText,detailedText); dialog.setIcon(MessageDialog::Information); dialog.setStandardButtons( StandardButtons(button0|button1|button2|button3)); dialog.exec(); return dialog.clickedButton(); } bool MessageDialog::open() { Q_ASSERT(m_item); if (m_isOpen) return false; m_isOpen=invokeMethod("open()"); return m_isOpen; } bool MessageDialog::close() { Q_ASSERT(m_item); if (!m_isOpen) return false; m_isOpen=!invokeMethod("close()"); return !m_isOpen; } bool MessageDialog::invokeMethod(QString methodSignature) { Q_ASSERT(m_item); int methodIndex; methodIndex=m_item->metaObject()->indexOfMethod( methodSignature.toLocal8Bit()); QMetaMethod method = m_item->metaObject()->method(methodIndex); return method.invoke(m_item,Qt::DirectConnection); } bool MessageDialog::setStrings( const QString &title, const QString &text, const QString informativeText, const QString detailedText) { bool success=true; success &= this->setItemProperty("title",title); success &= this->setItemProperty("text",text); success &= this->setItemProperty("informativeText",informativeText); success &= this->setItemProperty("detailedText",detailedText); return success; } void MessageDialog::initItem(Controller *controller) { m_engine=controller->engine(); Q_ASSERT(m_engine); QQmlComponent* myComponent=new QQmlComponent( m_engine, QUrl(QStringLiteral("qrc:/MessageDialog.qml"))); Q_ASSERT(myComponent); if (!myComponent->isReady()) { qWarning("%s", qPrintable(myComponent->errorString())); } QObject *myObject = myComponent->create(); Q_ASSERT(myObject); m_item = qobject_cast<QQuickItem*>(myObject); Q_ASSERT(m_item); QQmlApplicationEngine::setObjectOwnership( m_item,QQmlApplicationEngine::CppOwnership); } void MessageDialog::connectQMLSignals() { connect(m_item, SIGNAL(accepted()),this, SIGNAL(accepted())); connect(m_item, SIGNAL(apply()),this, SIGNAL(apply())); connect(m_item, SIGNAL(discard()),this, SIGNAL(discard())); connect(m_item, SIGNAL(help()),this, SIGNAL(help())); connect(m_item, SIGNAL(no()),this, SIGNAL(no())); connect(m_item, SIGNAL(rejected()),this, SIGNAL(rejected())); connect(m_item, SIGNAL(reset()),this, SIGNAL(reset())); connect(m_item, SIGNAL(yes()),this, SIGNAL(yes())); }

这是通讯员MessageDialog.qml

import QtQuick 2.4 import QtQuick.Controls 1.3 import QtQuick.Dialogs 1.2 Item{ id: baseItem property alias text: errorDialogItem.text property alias detailedText: errorDialogItem.detailedText property alias informativeText: errorDialogItem.informativeText property alias title: errorDialogItem.title property alias modality: errorDialogItem.modality property alias standardButtons: errorDialogItem.standardButtons property alias icon: errorDialogItem.icon property alias clickedButton: errorDialogItem.clickedButton property alias standardIconSource: errorDialogItem.standardIconSource signal accepted() signal apply() signal discard() signal help() signal no() signal rejected() signal reset() signal yes() function open() { return errorDialogItem.open() } function close() { return errorDialogItem.close() } MessageDialog { id: errorDialogItem objectName: "errorDialogItem" onAccepted: baseItem.accepted() onApply: baseItem.apply() onDiscard: baseItem.discard() onHelp: baseItem.help() onNo: baseItem.no() onRejected: baseItem.rejected() onReset: baseItem.reset() onYes: baseItem.yes() } }

我希望这可以帮助将来有人节省时间。

Answer 2

这是 SeDi 答案的替代方法。它没有完全开发，但可以根据您自己的需要简单轻松地进行修改。

示例实现

 MessageDialog::showCritcalError( myQmlEngine, "The sky is falling!" );

MessageDialog.h

#ifndef MESSAGEDIALOG_H
#define MESSAGEDIALOG_H

#include <QQmlEngine>

struct MessageDialog
{    
    static void showCritcalError( QQmlEngine *engine, const QString &message );
};

#endif // MESSAGEDIALOG_H

MessageDialog.cpp

#include "MessageDialog.h"

#include <QQmlComponent>
#include <QQuickItem>

// ---------------------------------

static const QString QML_RESOURCE_PREFIX( "qrc:/" );
static const QString DIALOG_QML( "MessgeDialog.qml" );

static const char *TITLE_PROP   = "dialogTitle";
static const char *ICON_PROP    = "dialogIcon";
static const char *TEXT_PROP    = "dialogText";
static const char *VISIBLE_PROP = "dialogVisible";

static const QString INFO_DEFAULT_TITLE(     "Information" );
static const QString WARNING_DEFAULT_TITLE(  "Warning" );
static const QString CRITICAL_DEFAULT_TITLE( "Error" );
static const QString QUESTION_DEFAULT_TITLE( "Question" );

static const int NO_ICON = 0,
               INFO_ICON = 1,
                 WARNING = 2,
           CRITICAL_ICON = 3,
           QUESTION_ICON = 4;

void showMessageDialog( QQmlEngine *engine,
    const QString &title, const int icon, const QString &text  )
{
    QQmlComponent component( engine, QUrl( QML_RESOURCE_PREFIX + DIALOG_QML ) );
    QQuickItem *item = qobject_cast<QQuickItem*>( component.create() );
    item->setProperty( TITLE_PROP,   title );
    item->setProperty( ICON_PROP,    icon );
    item->setProperty( TEXT_PROP,    text );
    item->setProperty( VISIBLE_PROP, true ); // must do last after setting other properties
}

// ---------------------------------

void MessageDialog::showCritcalError( QQmlEngine *engine, const QString &message )
{ showMessageDialog( engine, CRITICAL_DEFAULT_TITLE, CRITICAL_ICON, message ); }

MessageDialog.qml（在我的用例中列在 .qrc 中）

import QtQuick 2.2
import QtQuick.Dialogs 1.1

Item {
    property string dialogTitle: ""
    property int     dialogIcon: 0
    property string  dialogText: ""
    property bool dialogVisible: false
    MessageDialog {
        id: messageDialog
        title   : dialogTitle
        icon    : dialogIcon
        text    : dialogText
        visible : dialogVisible
        modality: Qt.ApplicationModal
    }
}

MessageDialog - 从 C++ 更改文本但屏幕上没有更新

MessageDialog - text change from c++ but no update on screen

dialog

dynamic

popup

qml