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read same data set twice ? [message #1710013]

Fri, 02 October 2015 16:06

Ivan Mising name

Messages: 32
Registered: July 2009

Member

Hi,

I just tried this logic and notice NatTable read twice same data set.
Is there anyway to prevent this happen ?

Thanks

this is the out put :
left side is column and right side is row.

0=0
0=1
0=2
0=0
0=1
0=2

----------------------------
IDataProvider myDataProvider = new IDataProvider() {

@Override
public int getColumnCount() {
return 5;//26;
}

@Override
public int getRowCount() {
return 1000;
}

@Override
public Object getDataValue(int columnIndex, int rowIndex) {

if( columnIndex == 0 ){//&& rowIndex == 0
System.out.println(columnIndex + "=" + rowIndex );
}
String columnLetter = String
.valueOf((char) ('A' + columnIndex));
String rowNumber = String.valueOf(rowIndex + 1);
return columnLetter + rowNumber;
}

@Override
public void setDataValue(int columnIndex, int rowIndex,
Object newValue) {
// Do nothing
}
};

DataLayer bodyDataLayer = new DataLayer(myDataProvider);

ViewportLayer viewportLayer = new ViewportLayer( bodyDataLayer );

natTable = new NatTable(this, viewportLayer);

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Re: read same data set twice ? [message #1710039 is a reply to message #1710013]

Fri, 02 October 2015 20:39

Dirk Fauth

Messages: 2902
Registered: July 2012

Senior Member

I would need to debug why getDataValue() is called twice. Maybe because of a repaint caused by a client are resize or the viewport initializiation. But it shouldn't be an issue as getDataValue() is called a lot of times, e.g. on scrolling as the table gets re-rendered on scrolling.

The real question is, why do you care about how often getDataValue() is called?

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Re: read same data set twice ? [message #1710043 is a reply to message #1710039]

Sat, 03 October 2015 04:38

Ivan Mising name

Messages: 32
Registered: July 2009

Member

Hi,

not only that it read the visible rows data event just a click to make the window focus. this is important as every row it needs to read an image thumbnail in. if visible rows read twice, am easily out of handle. and, i'm try to dispose the out of visible area images as well.

Thanks

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Re: read same data set twice ? [message #1710057 is a reply to message #1710043]

Sat, 03 October 2015 13:31

Dirk Fauth

Messages: 2902
Registered: July 2012

Senior Member

If you load resources in getDataValue() you might run into several issues. IMHO you should rethink your resource handling and look at JFace resources.

Also the disposal of resources that are out of the visible area is currently not supported in NatTable. At least I don't know a way to do this with the current code base. I think you already created a ticket for this.

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Re: read same data set twice ? [message #1710061 is a reply to message #1710057]

Sat, 03 October 2015 14:18

Ivan Mising name

Messages: 32
Registered: July 2009

Member

Yape, already. but is there anyway to prevent nattable read same data set twice ? Thanks

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Re: read same data set twice ? [message #1710063 is a reply to message #1710061]

Sat, 03 October 2015 14:36

Dirk Fauth

Messages: 2902
Registered: July 2012

Senior Member

So you either didn't read my previous posts or you didn't understand.

In short, no you can't prevent that. There is no magic loading mechanism. The data model is accessed directly and this happens all the time, on scrolling, reloading, refreshing, updates, ...

You should not perform long running tasks to access the data model there as it breaks the performance. And you should not deal with resources in the data provider, it is not its intention. And if accessing the data model multiple times creates resource handle issues, you are doing something wrong regarding resource handling and should rethink your resource handling strategy for loading thumbnail images. I already suggested the usage of JFace resources to avoid loading resources multiple times.

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Re: read same data set twice ? [message #1710089 is a reply to message #1710063]

Sun, 04 October 2015 07:41

Ivan Mising name

Messages: 32
Registered: July 2009

Member

Hi, thanks for your reply. for this topic. actually I just wanted to confirm, is it NatTable will always read same visible data set twice ? or is there anyway that I prevent that ? this nothing to do with dispose objects or not. Hope you understand what I means.... thanks and waiting your reply again. best regards

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Re: read same data set twice ? [message #1710098 is a reply to message #1710089]

Sun, 04 October 2015 08:06

Dirk Fauth

Messages: 2902
Registered: July 2012

Senior Member

Quote:

In short, no you can't prevent that. There is no magic loading mechanism. The data model is accessed directly and this happens all the time, on scrolling, reloading, refreshing, updates, ...

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