[Qgis-developer] Displaying map with QgsUniqueValueRenderer

[Marco Hugentobler]

Hi Satya,

Is "Dmg_zip" an attribute name or an attribute value?
You need to specify the attribute _value_ for which you want the symbol to 
apply. Additionally, you need to give the classification field index to the 
renderer, so that it knows in which attribute to look. 

You can see how the QGIS application itself does it. Look at the unique value 
dialog class QgsUniqueValueDialog.cpp/h.

All the best,
Marco

Am Mittwoch, 7. März 2007 17:17 schrieb satya satya:
> Hi Marco,
> I uncommented //mypRenderer->insertValue("point",symbol); , I changed
> "POINT" to "Dmg_zip" which is one of the attributes of my shape file.
> Unfortunately it displayed nothing. Do i need to iterate all the points in
> the shaped file??
> Thaking you
> regards
> satya
>
> On 3/7/07, Marco Hugentobler <marco.hugentobler at karto.baug.ethz.ch> wrote:
> > Hi Satya,
> >
> > Just use the Method QgsUniqueValueRenderer::insertValue(QString name,
> > QgsSymbol* symbol). The first parameter is the attribute value for which
> > the
> > symbol is valid, the second a pointer to your symbol (ok, 'name' is a
> > misleading name for the parameter...)
> >
> > In the code below, there is the outcommented line
> > //mypRenderer->insertValue("point",symbol);
> > I suppose "point" is not the attribute value for which you want the
> > symbol to
> > be applied? Try to replace it with the attribute value and see if it
> > works.
> >
> > If you want the symbol to be valid for all features, then you can use
> > QgsSingleSymbolRenderer, method
> > QgsSingleSymbolRenderer::addSymbol(QgsSymbol*)
> >
> > Best regards,
> > Marco
> >
> > Am Mittwoch, 7. März 2007 15:38 schrieb satya satya:
> > > Hi tim,
> > > Here is the code
> > >
> > > // QGIS Includes
> > > // Qt Includes
> > > // Std Includes
> > >
> > > int main(int argc, char ** argv)
> > > {
> > >   // Start the Application
> > >   QgsApplication app(argc, argv, true);
> > >
> > >   QString myPluginsDir        = "...../lib/qgis";
> > >   QString myLayerPath1         = ".............................
> > > .......shp"; QString myLayerBaseName1     = "....................shp";
> > >   QString myProviderName      = "ogr";
> > >   QgsSymbol* symbol;
> > >   QColor* color;
> > >
> > >
> > >     color = new QColor(255,0,0,255);
> > >
> > >         symbol = new QgsSymbol(color->rgb());
> > >
> > >   // Instantiate Provider Registry
> > >   QgsProviderRegistry::instance(myPluginsDir);
> > >   QgsVectorLayer * mypLayer = new QgsVectorLayer(myLayerPath1,
> > > myLayerBaseName1, myProviderName);
> > >
> > >    //get the field list associated with the layer
> > > std::vector<QgsField> myFields=mypLayer->fields();
> > >   QgsUniqueValueRenderer *mypRenderer=new
> > > QgsUniqueValueRenderer(mypLayer->vectorType());
> > >
> > >   mypRenderer->setClassificationField(5);
> > >
> > > symbol->setColor(Qt::red);
> > >   symbol->setFillColor(QColor(255,0,0));
> > >   symbol->setLabel("HELLO");
> > >   symbol->setPointSize (5);
> > >
> > >
> > >   std::deque<QString> myLayerSet;
> > >   mypLayer->setRenderer(mypRenderer);
> > > //mypRenderer->insertValue("point",symbol);
> > > if (mypLayer->isValid())
> > >   {
> > >     qDebug("Layer is valid");
> > >   }
> > >   else
> > >   {
> > >     qDebug("Layer is NOT valid");
> > >   }
> > >
> > >   // Add the Vector Layer to the Layer Registry
> > >
> > >   QgsMapLayerRegistry::instance()->addMapLayer(mypLayer, TRUE);
> > >     // Add the Layer to the Layer Set
> > >
> > >
> > >
> > >   myLayerSet.push_back(mypLayer->getLayerID());
> > >   mypLayer->setVisible(TRUE);
> > >
> > >
> > >
> > >   // Create the Map Canvas
> > >   QgsMapCanvas * mypMapCanvas = new QgsMapCanvas(0, 0);
> > >   mypMapCanvas->setExtent(mypLayer->extent());
> > >   // cbit qDebug(mypMapCanvas->extent().stringRep(2));
> > >
> > >   mypMapCanvas->enableAntiAliasing(true);
> > >   mypMapCanvas->setCanvasColor(QColor(255, 255, 255));
> > >   mypMapCanvas->freeze(false);
> > >   // Set the Map Canvas Layer Set
> > >   mypMapCanvas->setLayerSet(myLayerSet);
> > >   mypMapCanvas->setVisible(true);
> > >   mypMapCanvas->refresh();
> > >  // Start the Application Event Loop
> > > //cout<<marker_symbol->picture().toStdString()<<endl;
> > > app.exec();
> > >  //QgsMapCanvas myMapCanvas(0, 0);
> > >  QgsMapLayerRegistry::instance()->removeAllMapLayers();
> > > return 0;
> > > }
> > >
> > > I created symbol, but don't know how to add that to the unique value
> > > renderer.
> > >
> > > Thanking you
> > > cheers
> > > satya
> > >
> > > > On 3/5/07, Tim Sutton <tim at linfiniti.com> wrote:
> > > > > Hi
> > > > >
> > > > > How about posting code examples of what you have tried and we can
> >
> > try
> >
> > > > > to help you from there....
> > > > >
> > > > > Regards
> > > > >
> > > > > Tim
> > > > >
> > > > > 2007/3/5, satya satya <satya341 at gmail.com >:
> > > > > > Hello all,
> > > > > >               I am trying to develop a simple application using
> >
> > QGis
> >
> > > > > API.
> > > > >
> > > > > >  I have read all tutorials on QGis blog. I would like to use
> > > > > > "QgsUniqueValueRenderer" in my application to display features in
> > > > > > diff
> > > > > >
> > > > > > colors. I tried that  "QgsUniqueValueRenderer" , but no luck.
> > > > > >  could some body help me .
> > > > > >  cheers
> > > > > >  satya
> > > > > >
> > > > > > _______________________________________________
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> > > > >
> > > > > --
> > > > > --
> > > > > Tim Sutton
> > > > >
> > > > > Visit http://qgis.org for a great Open Source GIS
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