Qt 5.8,Windows 10。
快速控制 2 应用程序。在 QML 中,我有一个从 QAbstractListModel 派生的模型的 ListView。
在模型中,我有以下代码:
void MediaPlaylistModel::update()
{
beginResetModel();
{
std::unique_lock<std::mutex> lock(m_mutex);
m_ids = m_playlist->itemsIds();
}
endResetModel();
}
调用此方法后,QML 视图中没有任何反应:列表未更新。如果我返回然后转发(到带有 ListView 的页面)-它将包含更新的数据。模型对象实例始终相同。
难道我做错了什么?
更新#1:
我覆盖的唯一方法是:
QHash<int, QByteArray> roleNames() const override;
int rowCount(const QModelIndex &parent) const override;
QVariant data(const QModelIndex &index, int role) const override;
更新#2:
C++模型代码:
MediaPlaylistModel::MediaPlaylistModel(
QSharedPointer<AbstractMediaPlaylist> playlist,
QObject *parent) :
base_t(parent),
m_playlist(playlist)
{
Q_ASSERT(m_playlist);
connect(playlist.data(), &AbstractMediaPlaylist::changed,
this, &MediaPlaylistModel::update);
update();
}
QHash<int, QByteArray> MediaPlaylistModel::roleNames() const
{
QHash<int, QByteArray> result;
result[IdRole] = "id";
result[TitleRole] = "title";
result[DurationRole] = "duration";
return result;
}
void MediaPlaylistModel::update()
{
Q_ASSERT_SAME_THREAD;
beginResetModel();
{
std::unique_lock<std::mutex> lock(m_mutex);
m_ids = m_playlist->itemsIds();
}
endResetModel();
}
int MediaPlaylistModel::rowCount(
const QModelIndex &parent) const
{
Q_UNUSED(parent);
std::unique_lock<std::mutex> lock(m_mutex);
return static_cast<int>(m_ids.size());
}
QVariant MediaPlaylistModel::data(
const QModelIndex &index,
int role) const
{
auto row = static_cast<size_t>(index.row());
int id = 0;
{
std::unique_lock<std::mutex> lock(m_mutex);
if (row >= m_ids.size())
return QVariant();
id = m_ids[row];
}
if (role == IdRole)
return id;
QVariant result;
auto item = m_playlist->item(id);
switch(role)
{
case Qt::DisplayRole:
case TitleRole:
result = item.title;
break;
case DurationRole:
result = item.duration;
break;
}
return result;
}
QML 代码:
import QtQuick 2.7
import QtQuick.Controls 2.0
import com.company.application 1.0
Page
{
id : root
property int playlistId
property var playlistApi: App.playlists.playlist(playlistId)
ListView
{
id : playlist
anchors.fill: parent
model: playlistApi.model
delegate: ItemDelegate
{
text: model.title
width: parent.width
onClicked: App.player.play(playlistId, model.id)
}
ScrollIndicator.vertical: ScrollIndicator {}
}
}
更新#3:
当模型更新(添加一个项目)时,QML ListView 发生了一些奇怪的事情:除了它没有更新(并且它没有调用 MediaPlaylistModel::data 来检索新项目)之外,现有项目已经损坏。当我单击已存在的项目时,它的 model.id 属性始终为 0。例如,在应用程序启动时,其 model.id 为 24,添加一个项目后其 model.id 变为 0。
更新#4:
App.playlists.playlist(playlistId) 返回指向此类实例的指针:
class CppQmlPlaylistApi :
public QObject
{
Q_OBJECT
Q_PROPERTY(QObject* model READ model NOTIFY modelChanged)
Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged)
public:
explicit CppQmlPlaylistApi(
int playlistId,
QWeakPointer<CorePlaylistsManager> playlistsMgr,
QObject *parent = 0);
QObject* model() const;
QString title() const;
void setTitle(const QString &title);
signals:
void modelChanged();
void titleChanged();
void loadPlaylistRequested(int id);
protected slots:
void onPlaylistLoaded(int id);
void onPlaylistRemoved(int id);
protected:
int m_playlistId = 0;
QWeakPointer<CorePlaylistsManager> m_playlistsMgr;
QSharedPointer<QAbstractItemModel> m_model;
};