Qt Quick 从角色返回对象

Posted 2023-02-16

【中文标题】Qt Quick 从角色返回对象

【英文标题】：Qt Quick returning objects from roles

【发布时间】：2016-02-26 20:47:42

【问题描述】：

我正在尝试让角色返回一个对象。当我尝试访问 display.blockNumber 和 display.time 时遇到了未定义的错误

这是我的代码

blockdisplay.h:

#ifndef BLOCKDISPLAY_H
#define BLOCKDISPLAY_H

#include <QMetaType>

class BlockDisplay

public:
    BlockDisplay();
    BlockDisplay(int blocknum, long time);
    BlockDisplay(const BlockDisplay &other);
    ~BlockDisplay();

    int blockNumber() const;
    long time() const;

private:
    int m_blocknumber;
    long m_time;
;

Q_DECLARE_METATYPE(BlockDisplay)

#endif // BLOCKDISPLAY_H

blockdisplay.cpp:

#include "blockdisplay.h"

BlockDisplay::BlockDisplay() 



BlockDisplay::BlockDisplay(int blocknum, long time) 
    this->m_blocknumber = blocknum;
    this->m_time = time;


BlockDisplay::BlockDisplay(const BlockDisplay &other) 
    this->m_blocknumber = other.blockNumber();
    this->m_time = other.time();


BlockDisplay::~BlockDisplay() 



int BlockDisplay::blockNumber() const 
    return this->m_blocknumber;


long BlockDisplay::time() const 
    return this->m_time;

模型类.h：

#ifndef MODELCLASS_H
#define MODELCLASS_H

#include <QObject>
#include <QAbstractListModel>
#include <QStringListModel>

#include <blockchain.h>

class ModelClass : public QAbstractListModel

    Q_OBJECT

    Q_PROPERTY(qint32 blockheight READ blockheight)

protected:
    Blockchain bc;
    int first;
public:
    ModelClass();
    qint32 blockheight();
    void init();

    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
;

#endif // MODELCLASS_H

modelclass.cpp：

#include "modelclass.h"

#include <string.h>
#include <qdebug>

#include "blockdisplay.h"

using namespace std;

ModelClass::ModelClass()




void ModelClass::init() 
    bc.init();
    if ( !bc.Valid() )
        qDebug() << "invalid";
    else 
        bc.SeekToFirst();
        bc.Next();
        if ( !bc.Valid() )
            qDebug() << "invalid";
        else
            first = bc.GetCurrentBlock().signedhead().head().num();
    

    //setProperty("blockheight",bc.GetBlockHeight());


qint32 ModelClass::blockheight() 
    return bc.GetBlockHeight();


int ModelClass::rowCount(const QModelIndex &parent) const 
    //qInfo() << " 0test " << bc.GetBlockHeight();

    return bc.GetBlockHeight() - first;


QVariant ModelClass::data(const QModelIndex & index, int role) const 
    qInfo() << " 1test " << index;
    int row = bc.GetBlockHeight() - index.row();// + 1 + first;
    if (index.isValid()) 

        bc.Seek(row);

        if (bc.Valid()) 
            if (role == Qt::DisplayRole) 
                int blocknum = bc.GetCurrentBlock().signedhead().head().num();
                long timestamp = bc.GetCurrentBlock().signedhead().head().timestamp();

                BlockDisplay dsplyblocknum, timestamp;
                QVariant var = QVariant::fromValue(dsply);
                return var;
            
        
    

    return QVariant();

来自block.qml的sn-p：

Component 
    id: gridComp
    Row 
        Text 
            text: display.blockNumber + " "

            MouseArea 
                anchors.fill: parent
                onClicked: 
                    list.currentIndex = index;
                    ld.setSource("detail.qml")
                
            
        
        Text 
            text: display.time + " "
        
    

【参考方案1】：

我认为Q_DECLARE_METATYPE(BlockDisplay) 还不够。如果你想在 QML 中使用它的属性，你必须使用Q_PROPERTY 宏来创建properties，就像你为ModelClass 所做的那样。您可能还需要致电qRegisterMetaType

添加 Q_DECLARE_METATYPE() 使所有基于模板的函数都知道该类型，包括 QVariant。请注意，如果您打算在排队的信号和槽连接或 QObject 的属性系统中使用该类型，您还必须调用 qRegisterMetaType()，因为名称是在运行时解析的。