我在里面有listview的滚动视图:
ScrollView{
anchors.fill: parent
ListView{
id: lvCommitsBranch
model: git.getCommitsBranch();
clip: true
delegate: Rectangle {
height: 100
width: parent.width
Text {
anchors.left: parent.left
font.bold: true
text:model.author
id:txtName
}
Text{
anchors.left: parent.left
anchors.top:txtName.bottom
font.pixelSize: 10
text:model.email
id: txtEmail
}
Text {
anchors.left: parent.left
anchors.top:txtEmail.bottom
text: model.message + ' ' + model.hash
id: txtMsg
}
MouseArea{
anchors.fill: parent
onClicked: {
lvCommitsBranch.currentIndex = index;
console.log('Msg: ' + model.message);
console.log('Hash: ' + model.hash);
}
acceptedButtons: Qt.LeftButton | Qt.RightButton
}
}
}
}
问题在于,当我滚动某些项目时会消失(每次都是随机的,有时我必须快速滚动但不总是)。
当我点击尚未消失的项目时,我会在所有模型的属性上获得undefined
。当Mousearea的onclick
被触发时,它会打印以下内容:
qml:Msg:undefined
qml:Hash:undefined
我从我的git
自定义组件返回的方法(QAbstractListModel)中获取模型信息。
这是我的QAbstractListModel:
头:
class CommitsBranch : public QAbstractListModel
{
Q_OBJECT
public:
enum Roles {
AuthorRole,
EMailRole,
MsgRole,
DateRole,
HashRole
};
explicit CommitsBranch(QObject *parent = 0);
CommitsBranch(Repository *repo);
public:
virtual int rowCount(const QModelIndex &parent) const override;
virtual QVariant data(const QModelIndex &index, int role) const override;
protected:
// return the roles mapping to be used by QML
virtual QHash<int, QByteArray> roleNames() const override;
private:
QList<Commit> m_data;
QHash<int, QByteArray> m_roleNames;
};
.cpp的:
CommitsBranch::CommitsBranch(QObject *parent)
: QAbstractListModel(parent)
{
}
CommitsBranch::CommitsBranch(Repository *repo)
{
m_roleNames[AuthorRole] = "author";
m_roleNames[EMailRole] = "email";
m_roleNames[MsgRole] = "message";
m_roleNames[DateRole] = "date";
m_roleNames[HashRole] = "hash";
/*
here we append the m_data (QList) Items using libgit2 methods
*/
}
int CommitsBranch::rowCount(const QModelIndex &parent) const
{
Q_UNUSED(parent);
return m_data.count();
}
QVariant CommitsBranch::data(const QModelIndex &index, int role) const
{
// this function returns the required data
}
QHash<int, QByteArray> CommitsBranch::roleNames() const
{
return m_roleNames;
}
git只是一个继承自QObject的类,它有以下方法:
Q_INVOKABLE QObject* getCommitsBranch();
QObject *Git::getCommitsBranch()
{
CommitsBranch* files = new CommitsBranch(repo.data());
return files;
}
如果没有scrollview,我会得到相同的行为。
编辑: 如果我使用大量提交的存储库(列表视图中有更多行),即使增加cacheBuffer也无济于事,如果我快速滚动,所有项目都将消失。
答案 0 :(得分:3)
这里的问题是,默认情况下,如果你返回一个QObject *,它会将所有权转移到QML。
http://doc.qt.io/qt-5/qtqml-cppintegration-data.html#data-ownership
此规则的例外情况是从一个QObject返回时 显式C ++方法调用:在这种情况下,QML引擎假定 除非对象的所有权具有,否则对象的所有权 显式设置为通过调用保留C ++ QQmlEngine :: setObjectOwnership()与QQmlEngine :: CppOwnership 指定。
您必须手动设置返回的QObject *所有权,因此它不会被QML引擎销毁:
QObject *Git::getCommitsBranch()
{
CommitsBranch* files = new CommitsBranch(repo.data());
QQmlEngine::setObjectOwnership(files, QQmlEngine::CppOwnership)
return files;
}
请注意,由于永远不会删除CommitsBranch
对象,因此会出现内存泄漏。但至少你的QML项目不应该消失了!
编辑:正如所建议你可以这样做以避免内存泄漏:
// CommitsBranch Constructor
CommitsBranch::CommitsBranch(Repository *repo, QObject *parent) :
QAbstractListModel(parent) { /*stuff*/ }
QObject *Git::getCommitsBranch()
{
// Setting ownership is not necessary if you pass the parent to the QAbstractListModel
CommitsBranch* commits = new CommitsBranch(repo.data(), this);
return files;
}