[SOLVED] ListView's flickable problems

alex2202375

Alicemirror: I don't think this is a memory problem, because I use QAbstractListModel to provide the data, and following is the data function that I used:
@QVariant RFileModel::data(const QModelIndex & index, int /role/) const {
int row = index.row();
return data(row);
}

QVariant RFileModel::data(int row) const {
// return QVariant();
if (row < m_file_line_pos.count()) {
if (m_file->seek(m_file_line_pos[row])) {
QTextStream stream(m_file);
stream.setCodec(m_codec);
stream.setAutoDetectUnicode(true);
QString str = stream.readLine();
if (str.length() || !m_file->atEnd()) {
qDebug()<<"Read str row"<<row
<<"pos"<<m_file_line_pos[row]
<<"length"<<str.length()<<str;
return str+KNewLine;
}
else {
qDebug()<<"read file line failed, line number"<<row
<<"Position"<<m_file_line_pos[row]
<<m_file->errorString();
}
}
else {
qDebug()<<"could not seek to position/line"<<m_file_line_pos[row]<<row;
}
}
else {
qDebug()<<"row number is too large:row/max"<<row<<m_file_line_pos.count();
}
return QVariant();
}@

Alicemirror

Thank yo Alex, just a ping :) I'll answer to this shortly

Milnadar

still actual

mbrasser

[quote author="Milnadar" date="1316020663"]I noticed that when (vertical) listView's items has different height, contentHeight value doesn't equal to height of all items. When changing ListView's height, contentHeight may be larger or smaller than it should be. Why is it so? How does ListView count it's contentHeight?[/quote]

When items in a vertical ListView don't have a fixed height, contentHeight is estimated. This is to avoid the cost of instantiating every item in order to query their actual height.

Regards,
Michael

Mixa84

Im sorry to bring this topic from the dead, but I still dont see what is the solution to this problem and I need to solve this.

Here is the example of the code on which I`m trying to resolve the problem with contentHeight change and also with a problem when you go to positionViewAtEnd() contentY get some strange values:

@
import QtQuick 1.1

Rectangle
{
width: 360
height: 360

ListView
{
    id: lv
    anchors.fill: parent
    anchors.bottomMargin: 50
    spacing: 5
    model: msgmodel
    delegate:
        Rectangle
        {
            id: rect;
            width: lv.width;
            height: txt.height;
            Text
            {
                id: txt;

                width: 50;
                anchors.topMargin: 5;

                wrapMode: Text.WordWrap;
                text: " contentY: " + lv.contentY + "|" + lv.contentHeight + " y: " + y + " " + msgtext;
            }
        }
}

Text
{
    id: btn;
    objectName: "btn";

    signal add();

    text: "Click to move at end"
    anchors.bottom: parent.bottom
    MouseArea
    {
        anchors.fill: parent
        onReleased:  lv.positionViewAtEnd();
    }
}

}
@

Every time I go to view end contentY at the top of the view goes more in negative value.

EDIT: I have also tried this in QtQuick 2.0 and it is working better but it still has problem when going to view end. But this time instead of going into negative value, contentY increase its value.

Mixa84

Is there any solution to this when you have ListView items with variable height?

Milnadar

Hi Mixa84.

Yes, there is a solution, but it is about to implement your own listVew .

I mark this topic as solved.

mdrost

In my opinion ListView should be doing what it says in the docs, even if it is slow.

Kieren

Thank you for the good discussion.
Helped me a lot to understand my problem.

Even so it is kind of disappointing, that we can't even use the sizeHintRole for ListViews.
Or have an option to supply the ListView with the correct contentHeight, so it doesn't try calculate it on its own...

I've the idea of wrapping the actual list view into another flick able object to kind of wrap the broken scrolling with an item i can control the scrolling better. If it works I'll paste it here.

Pradip

@Milnadar
Hi, Milnadar,

I am stuck in same problem. You have discussed here everything except solution.
Can you please tell me the way to proceed with Listview and Scrollbar problem with different height's delegates.

Berzeck

Well I found another solution. I post here so maybe it helps sombedody.

You need to declare a global property which stores the height. For example : reViewHeight
Put the ListView inside a transparent Rectangle: rcView, and put the rectangle inside the ScrollView
Add: Component.onCompleted: { reViewHeight = reViewHeight + height} in your delegate definition
In the ListView add: onCountChanged: { rcView.height = reViewHeight }

Done !

crazymax

up
@Berzeck it didn't help me
Any another solution for this problem?