Question

我有以下QML ListView：

ListView
{
    antialiasing: true
    Layout.alignment: Qt.AlignCenter
    Layout.fillWidth: true

    Layout.preferredHeight: 128

    clip: true

    spacing: 64

    model: uePeopleModel

    orientation: ListView.Horizontal

    highlightFollowsCurrentItem: true

    delegate: Image
    {
        source: "image://uePeopleModel/"+model.ueRoleImage

        scale: parent.ListView.isCurrentItem ? 1.5 : 1

        Behavior on scale
        {
            NumberAnimation
            {
                duration: 200
            }   // NumberAnimation
        }   // Behavior
    }   // delegate

    preferredHighlightBegin: width/2
    preferredHighlightEnd: width /2
    highlightRangeMode: ListView.StrictlyEnforceRange
    Component.onCompleted:
    {
        currentIndex=count/2
        print("ListView.count: "+count)
        print("ListView.currentIndex: "+currentIndex)
        print("ListView.currentItem: "+currentItem)
    }   // Component.onCompleted
}   // ListView

现在，当我运行app时，ListView中会显示项目（图像），但调试print语句报告：

qml：ListView.count：0 qml：ListView.currentIndex：0 qml： ListView.currentItem：null

因此我无法获得＆＃34;居中的项目＆＃34;。为什么？！根据{{1}}的声明ListView，项目既不会缩放，为什么？

scale: parent.ListView.isCurrentItem ? 1.5 : 1

这是它的实施：

Here is coresponding model header file:
#ifndef UEPEOPLEMODEL_H
#define UEPEOPLEMODEL_H

#include <QImage>
#include <QVariant>
#include <QStringList>
#include <QHash>
#include <QByteArray>
#include <QSqlError>
#include <QSqlQueryModel>
#include <QSqlRecord>
#include <QModelIndex>
#include <QQuickImageProvider>
#include <QByteArray>
#include <QSqlRecord>
#include <QSqlQuery>

#include "../settings/uedefaults.h"
#include "../core/uedatabaseconnectionstatus.h"
#include "../core/uetypes.h"
#include "../core/ueapplicationstatus.h"
#include "../core/ueuserrecord.h"

class UePeopleModel : public QSqlQueryModel,
                      public QQuickImageProvider
{
    Q_OBJECT

private:
    QSqlDatabase m_ueDb;

private:
    QSqlDatabase ueDatabase() const
        { return this->m_ueDb; }
    void ueSetDatabase(const QSqlDatabase& database)
        { this->m_ueDb=database; }
    QImage ueImage(const QString& id) const;

public:
    UePeopleModel(QObject *parent=0);
    ~UePeopleModel();

    QVariant data(const QModelIndex &index,
                  int role) const Q_DECL_OVERRIDE;
    QImage requestImage(const QString &id,
                        QSize *size,
                        const QSize &requestedSize);
    UeTypeRoles roleNames() const;
    void ueConnectToDatabase();
    UeTypeUsers* ueFetchUsers();

public:
    static const int ueRoleName=Qt::UserRole+1;
    static const int ueRoleImage=Qt::UserRole+2;
    static const int ueRolePassword=Qt::UserRole+3;

signals:
    void ueSignalDatabaseConnectionChanged(const UeDatabaseConnectionStatus::UeTypeDatabaseConnectionStatus& newStatus);
};

#endif // UEPEOPLEMODEL_H

模特好吗？

根据用户@Mido的回答，我已将#include "uepeoplemodel.h" UePeopleModel::UePeopleModel(QObject* parent) : QSqlQueryModel(parent), QQuickImageProvider(QQmlImageProviderBase::Image, QQmlImageProviderBase::ForceAsynchronousImageLoading) { emit this->ueSignalDatabaseConnectionChanged(UeDatabaseConnectionStatus::NOT_CONNECTED); } // default constructor UePeopleModel::~UePeopleModel() { QString connName=this->ueDatabase().connectionName(); this->ueDatabase().close(); this->ueSetDatabase(QSqlDatabase()); this->ueDatabase().removeDatabase(connName); emit this->ueSignalDatabaseConnectionChanged(UeDatabaseConnectionStatus::NOT_CONNECTED); } // default destructor QVariant UePeopleModel::data(const QModelIndex &index, int role) const { switch(role) { case ueRoleImage: { return QString::number(index.row()); } break; // case case ueRoleName: { return this->record(index.row()).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_NAME).toString(); } break; // case case ueRolePassword: { return this->record(index.row()).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_APPPASSWORD).toString(); } break; // case default: { return QSqlQueryModel::data(index, role); } break; // default } // switch return QVariant(); } // data QImage UePeopleModel::ueImage(const QString &id) const { return QImage::fromData(this->record(id.toInt()).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_IMAGE).toByteArray(), "PNG").scaled(UeDefaults::UeGraphics::PEOPLE_IMAGE_WIDTH, UeDefaults::UeGraphics::PEOPLE_IMAGE_HEIGHT, Qt::IgnoreAspectRatio, Qt::SmoothTransformation); } // ueImage QImage UePeopleModel::requestImage(const QString &id, QSize *size, const QSize &requestedSize) { Q_UNUSED(size) Q_UNUSED(requestedSize); // if(size) // { // *size=QSize(UeDefaults::UeGraphics::PEOPLE_IMAGE_WIDTH, // UeDefaults::UeGraphics::PEOPLE_IMAGE_HEIGHT); // } // if //return this->ueImage(id); return QImage::fromData(this->record(id.toInt()).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_IMAGE).toByteArray(), "PNG").scaled(UeDefaults::UeGraphics::PEOPLE_IMAGE_WIDTH, UeDefaults::UeGraphics::PEOPLE_IMAGE_HEIGHT, Qt::IgnoreAspectRatio, Qt::SmoothTransformation); } // requestImage UeTypeRoles UePeopleModel::roleNames() const { UeTypeRoles roles; const int iRoleName=UePeopleModel::ueRoleName; const int iRoleImage=UePeopleModel::ueRoleImage; const int iRolePassword=UePeopleModel::ueRolePassword; roles.insert(iRoleName, "ueRoleName"); roles.insert(iRoleImage, "ueRoleImage"); roles.insert(iRolePassword, "ueRolePassword"); return roles; } // roleNames void UePeopleModel::ueConnectToDatabase() { if(!QSqlDatabase::connectionNames().contains(UePosDatabase::UeDatabaseConnectionNames::DATABASE_CONNECTION_NAME_PEOPLE, Qt::CaseInsensitive)) { this->ueSetDatabase(QSqlDatabase::addDatabase(UePosDatabase::DATABASE_DRIVER, UePosDatabase::UeDatabaseConnectionNames::DATABASE_CONNECTION_NAME_PEOPLE)); } // if this->ueDatabase().setHostName(UePosDatabase::UeDatabaseConnectionParameters::DATABASE_HOSTNAME); this->ueDatabase().setDatabaseName(UePosDatabase::UeDatabaseConnectionParameters::DATABASE_NAME); this->ueDatabase().setUserName(UePosDatabase::UeDatabaseConnectionParameters::DATABASE_USERNAME); this->ueDatabase().setPassword(UePosDatabase::UeDatabaseConnectionParameters::DATABASE_PASSWORD); if(this->ueDatabase().open()) { this->setQuery(UePosDatabase::UeSqlQueries::UeTablePeople::SQL_QUERY_GET_ALL_PEOPLE, this->ueDatabase()); emit this->ueSignalDatabaseConnectionChanged(UeDatabaseConnectionStatus::CONNECTED); } else { emit this->ueSignalDatabaseConnectionChanged(UeDatabaseConnectionStatus::NOT_CONNECTED); } // if } // ueConnectToDatabase UeTypeUsers* UePeopleModel::ueFetchUsers() { UeTypeUsers* users=new UeTypeUsers(); for(int iIndex=0; iIndex<this->record().count(); iIndex++) { users->append(new UeUserRecord(this, this->record(iIndex).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_ID).toString(), this->record(iIndex).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_NAME).toString(), this->record(iIndex).value(UePosDatabase::UeTableIndexes::UeTablePeople::INDEX_APPPASSWORD).toString())); } // for return users; } // ueFetchUsers重新实现为：

ListView

我还在函数ListView { id: ueUserInfoListView antialiasing: true Layout.alignment: Qt.AlignCenter Layout.fillWidth: true Layout.preferredHeight: 128 clip: true spacing: 64 model: uePeopleModel orientation: ListView.Horizontal highlightFollowsCurrentItem: false delegate: Image { id: ueUserInfoListViewDelegate source: "image://uePeopleModel/"+model.ueRoleImage opacity: 0.3 function ueDoOpacity() { if(ueUserInfoListViewDelegate===parent.ListView.currentItem) opacity=1.0 else opacity=0.3 print(parent.ListView.currentIndex) } Behavior on opacity { NumberAnimation { duration: 300 } // NumberAnimation } // Behavior Component.onCompleted: { ueUserInfoListViewDelegate.focusChanged.connect(ueDoOpacity) } // Component.onCompleted } // delegate Component.onCompleted: { preferredHighlightBegin: width/2 preferredHighlightEnd: width /2 highlightRangeMode: ListView.StrictlyEnforceRange currentIndex=count/2 } // Component.onCompleted } // ListView中添加了print(parent.ListView.currentIndex) 在节目开始时我得到：

qml：undefined

如果我滚动左/右ueDoOpacity的项目，则不会再次调用该函数。为什么呢？！

我已使用ListView替换目标媒体资源scale，此处已升级opacity：

ListView

Answer 1

我不知道为什么你的比例没有变化，解决方法是创建一个函数doScale并将它连接到focusChanged信号，试试这个例子：

import QtQuick 2.0 
import QtQuick.Layouts 1.2
ListView
{
    id:idList
    antialiasing: true
    Layout.alignment: Qt.AlignCenter
    Layout.fillWidth: true
    width:200
    height:200
    Layout.preferredHeight: 128

    clip: true

    spacing: 10

    model: 3

    orientation: ListView.Horizontal

    highlightFollowsCurrentItem: true

    delegate: Rectangle
    {
    id:obj
    // source: "image://uePeopleModel/"+model.ueRoleImage
    color:"yellow"
    width:30
    height:30

    function doScale()
    {
        if(obj === idList.currentItem)
            obj.scale = 1.5
        else
            obj.scale = 1.0
    }
    //scale: parent.ListView.isCurrentItem ? 1.5 : 1
    Component.onCompleted:
    {
        obj.focusChanged.connect(doScale)
    }
    Behavior on scale
    {
        NumberAnimation
        {
            duration: 300
        }   // NumberAnimation
    }   // Behavior
}   // delegate

preferredHighlightBegin: width/2
preferredHighlightEnd: width /2
highlightRangeMode: ListView.StrictlyEnforceRange
Component.onCompleted:
{
    currentIndex=count/2
    print("ListView.count: "+count)
    print("ListView.currentIndex: "+currentIndex)
    print("ListView.currentItem: "+currentItem)
}   // Component.onCompleted
}

QML ListView.count返回0，但在其中看到委托（图像）

1 个答案: