Attribute error when loading rasters in QGIS TOC in plugin

Question

I am trying to display field names dynamically inside a widget based on the number of fields in vector layer selected in combo box. When i load a raster inside QGIS TOC and a vector layer, it is raising an error as shown below

AttributeError: 'OpenlayersLayer' object has no attribute 'pendingFields'

Below is my code

    def addLayerNames(self):
     self.dlg.comboBox.clear()
     for i in reversed(range(self.dlg.verticalLayout.count())):
        self.dlg.verticalLayout.itemAt(i).widget().setParent(None)
     layers = QgsMapLayerRegistry.instance().mapLayers().values()
     layer_list = []
      for layer in layers:
        if layer.type() == QgsMapLayer.VectorLayer:
            layer_list.append(layer.name())
      self.dlg.comboBox.addItems(layer_list)
      selectedLayerIndex = self.dlg.comboBox.currentIndex()
      print selectedLayerIndex
      selectedLayer = layers[selectedLayerIndex]
      print selectedLayer
      fields = selectedLayer.pendingFields()
      fieldnames = [field.name() for field in fields]
      for i,field in enumerate(fieldnames):
        self.labels = QLabel()
        self.linedit = QLineEdit()
        self.labels.setText(field)
        #self.flay = QFormLayout()
        #self.le = QLineEdit()
        self.linedit.setFixedWidth(200)
        self.dlg.verticalLayout.addRow(field, self.linedit)
        #self.linedit.setFixedWidth(100)
        #self.dlg.verticalLayout.addLayout(self.flay)
        #self.dlg.verticalLayout.addWidget(self.linedit)
        request = QgsFeatureRequest().setFilterFid(0)
        layer.setSelectedFeatures([0])
        self.iface.actionZoomToSelected().trigger()
        feat = layer.getFeatures(request).next()
        self.linedit.setText(str(feat[i]))
        self.linedit.setObjectName(field)
        self.dlg.pushButton.setEnabled(False)
        self.lineedits.append(self.linedit)

Answer 1

I think the error is arising because you are calling the index value

selectedLayerIndex = self.dlg.comboBox.currentIndex()

and using this to identify the loaded layers

layers = QgsMapLayerRegistry.instance().mapLayers().values()
...
selectedLayer = layers[selectedLayerIndex]

So if you select a layer from your widget which has an index of 2, can you ensure that the layers in the Layer Panel are ordered so that the 3rd layer is not a raster?

---

Another approach (probably a little safer) is to match the layer by name and not with an index. Perhaps something like:

layers = QgsMapLayerRegistry.instance().mapLayers().values()
layer_list = []
for layer in layers:
if layer.type() == QgsMapLayer.VectorLayer:
    layer_list.append(layer.name())
self.dlg.comboBox.addItems(layer_list)
# Get text of selected layer's name
selectedLayerIndex = self.dlg.comboBox.currentText()
print selectedLayerIndex
# Match selected name with layer from panel
selectedLayer = QgsMapLayerRegistry.instance().mapLayersByName(str(selectedLayerIndex))[0]
print selectedLayer
fields = selectedLayer.pendingFields()