Solved How to modify the data in the model and update the view when new data is received from external?
-
@JonB : As you see in my code i read the Json file only ones i..e during initialization with empty values. Later i just want to update the values but not read again the file. Second point how would you suggest me to implement in my design or code? Example would be nice. Thank you.
-
Re-implement
setData
-
@SGaist: How would i provide the index values? I am really sorry, because somehow i am not able to understand this trick of updating my data (categories_) in model, i.e. how do i get index from my data and call setData? I would really appreciate if you could show in my code? This would then later emit dataChanged which will achieve my goal.
-
How exactly are you getting new data ?
What are these new data ?
One object update ?
Several objects update ?
How do they fit in your model internal representation ? -
@SGaist : I am getting this data when user clicks left mouse button. I have slot, so when user clicks button some magic is done and later i save in model member variable Info_.
The NewStructInfo looks like this:
struct NewStructInfo{
double x;
double y;
} Info_;
So now my model data categories_ looks something like this:
```
Property ----------------------------------------- Value
-->Coordinates(categoryitem pointer)
------X (scenariopropertyitem1 pointer type) ------ "Empty"
------Y (scenariopropertyitem pointer type) -------- "Empty"The above structure you can see in parsejsonobject member function. Now in the above categories_ model data i have iterate along category->secnariopropertyitem and look for the name i,e,
if(scenariopropertyitem->name == x)
// scenariopropertyitem pointer has name as class member
scenariopropertyitem->setValue(QVariant(Info_.X));
Now somehow dataChanged(??,??,Qt::displayrole) has to be called. -
Since you have to go through your model to find the correct item to update, you should already have the index matching the
scenariopropertyitem
you found, no ? -
@SGaist : How would i access it or get the index of the item? Meanwhile would you suggest me to use third option from this answer: https://stackoverflow.com/questions/29921041/getting-the-index-for-a-given-item-in-a-qtreeview-model-application.
Could you provide an example? -
This post is deleted! -
This post is deleted! -
What I always suggest is that if you are not 100% confident in your model design (and, believe me, it's a hard) just use
QAbstractItemModel* model = new QStandardItemModel(parent)
. Then use insertRows, insertColumns, and setData to setup your model -
In my Model.cpp i did the following:
emit beginResetModel(); for (auto& category : categories_) { category->entryAt(0)->setValue(1); // for testing i just set randomly my data value to 1 } emit endResetModel();
But after above changes the view is not displaying the new values.
-
@VInay123
I don't see anyentryAt()
function in Qt. So what type iscategory
, what doescategory->entryAt(0)->setValue(1)
do in the way of setting anything in the model?? -
@JonB: If you see my code Category is a class which has entryAt() function which returns back the propertyitem. So here i am setting the model data i.e. my categories_ member variable in the model class.
-
@VInay123
OK forentryAt()
. But where in your code doesentryAt(0)->setValue(1)
callQAbstractModel::setData()
(http://doc.qt.io/qt-5/qabstractitemmodel.html#setData)? Where is the http://doc.qt.io/qt-5/qabstractitemmodel.html#dataChanged signal being emitted? -
@JonB: That is the problem i am facing. I do not know how to call setData which in turn emits the signal dataChanged. I do not know how to get the indexes. Here the data is only coming from the "Info_" variable. If the it was via delegates or adapters i could easily get the indexes and call setData. But in my case i get in a structure and go through each item and update its value. Could you please show me how can i achieve this in my code i.e. change the value via setData?
-
@VInay123
Your code is way too big for me to wade through.-
If you are using
QAbstractModel
, you are using a model which holds data in rows & columns, right? -
When you put some data (received from JSON parsing or whatever), you have to decide where in the model's row/column you want to put this data, right?
-
Given that
row
&column
, you can construct aQModelIndex()
(http://doc.qt.io/qt-5/qabstractitemmodel.html#createIndex) for the data. -
Then you can pass that to your
Model::setData()
to set the value, andemit dataChanged(index, index)
to notify your view to update.
-
-
@JonB : Thank you. I implemented as following in my model:
QModelIndex index = createIndex(1, 1, categories_[0]->entryAt(0)); this->setData(index, 11, Qt::EditRole);
It is changing the value clearly. But in the view its not being displayed.
-
@VInay123
Well at least we're getting somewhere! Check the return result of yoursetData()
, maybe it's failing? Does (row, column) of (1, 1) exist in your model (else you need toinsertRows()
etc.)? Is thatsetData()
call indeed going into yourModel::setData()
and doing theemit dataChanged()
there (use a debugger or debug/print statements)? There's no point using bothbeginResetModel()
&dataChanged()
, and certainly notdataChanged()
while still inside thebeginResetModel()
before thenedRestModel()
. Change your code accordingly. -
@VInay123 said in How to modify the data in the model and update the view when new data is received from external?:
CategoryItem& parentItem = currentItem->parentItem();
return createIndex(currentItem->row(), 0, &parentItem);This is using the address of a temp item, it will not work.
QString data = file.readAll();
does not handle win/lunix line endings and encodings, use QString data = QTextStream(&file).readAll();
Use the model test to make sure your subclass works correctly
-
@JonB: Yes, I just call the setData ane here i have printed the changed:
if (role == Qt::EditRole && index.column() == 1 && index.isValid()) { auto currentItem = static_cast<ScenarioPropertyItem*>(index.internalPointer()); if (currentItem) { currentItem->setValue(value); qDebug() << currentItem->data(index.column()); emit dataChanged(index, index); return true; } }
The value is being changed here. The output looks like
QVariant(int, 11)
I have included a debug output in Data() but this is printing the default values that is empty("").
QVariantModel::data(const QModelIndex& index, int role /*= Qt::DisplayRole*/) const { if (!index.isValid()) { return QVariant(); } if (role == Qt::DisplayRole && isCategory(index)) { const auto currentCategory = static_cast<CategoryItem*>(index.internalPointer()); if (index.column() == 0) { return currentCategory->displayName(); } else { return QVariant(); } } const auto currentItem = static_cast<ScenarioPropertyItem*>(index.internalPointer()); if (role == Qt::DisplayRole && !isCategory(index)) { qDebug() << currentItem->data(index.column()); // Here its empty return currentItem->data(index.column()); } return QVariant(); }