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QGIS Plugin Development

QGIS Plugin Development. Xing Kang, Yan-ting Liau , Ngoc Nguyen Hong, Michael Palmer. Overview. What is QGIS? What were our goals? QT Framework GUI Implementation Methods Implemented Weights Matrix Creation ESDA – Moran’s I Spatial Dynamics – Spatial Markov

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QGIS Plugin Development

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  1. QGIS Plugin Development Xing Kang, Yan-ting Liau, Ngoc Nguyen Hong, Michael Palmer

  2. Overview • What is QGIS? • What were our goals? • QT Framework • GUI Implementation • Methods Implemented • Weights Matrix Creation • ESDA – Moran’s I • Spatial Dynamics – Spatial Markov • QGIS PySalPlugin in Action!

  3. QGIS (Quantum GIS) • Open source GIS • Small lightweight • Easy to learn • GNU GPL License

  4. Goals: Pruning the PySal Tree

  5. Why Use QT? • QGIS is written using QT Library • Why did they use QT? • Cross Platform • Widely used (Photoshop and Skype also use QT) • What we liked • Fast rough development with WYSISYG Editor • Fine tune the code afterwards

  6. Signals in QT • User actions generate signals • use signals to change other widgets in the Editor • Handle signals with python functions The function name corresponds to the specific signal @pyqtSignature('int') #prevents actions being handled twice defon_sourceLayer_currentIndexChanged(self,i): l = self.layers[i] self.lcount = l.featureCount() self.ui.horizontalSlider.setMaximum(self.lcount-1) self.ui.horizontalSlider.setTickInterval((self.lcount-1)/10 or 1) select the layer with the index i Use a method of Layer Update a GUI Widget Update a GUI Widget

  7. Design Decisions • Use the PySal splatter-chart to organize our plugin • PySalMenuBar. • Each Branch is a submenu. • Each Node is an Action in the submenu.

  8. One quick python trick • Instead of adding another if statement • Python returns the last variable read for boolean logic. • Remember False = (0, “”, None) True = (all else) • .setTickInterval((self.lcount-1)/10 or 1) use (self.lcount-1)/10 unless it equals 0 then use 1 Numbers Strings

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