Changing layer id in QGIS

Question

I use QgsLayerDefinition.loadLayerDefinition(path, project, rootGroup) in my code. But this method changes ids of loaded layers. I need the codes to be old. Is there any way to change ids (for example any custom) of layers after loading layer definitions? Or have any other ideas?

johnzet · Accepted Answer

To solve my problem, it was enough for me to use the idea of methods loadLayerDefinition, using the minimum functionality of these methods (+I added some restriction).
def loadLayerDefinitionCustom(self, path, project, rootGroup):
    file = QFile(path)
    doc = QtXml.QDomDocument()
    doc.setContent(file)

context = QgsReadWriteContext()
    context.setPathResolver( QgsPathResolver(path))
    context.setProjectTranslator(project)
    return self.loadLayerDefinitionDocCustom( doc, project, rootGroup, context )

def loadLayerDefinitionDocCustom(self, doc, project, rootGroup, context):
    root = QgsLayerTreeGroup()

# # check for id layers in project
    # map_layers = list(QgsProject.instance().mapLayers().keys())
    # treeLayerNodes = doc.elementsByTagName("maplayer")
    # for i in range(treeLayerNodes.count()):
    #     node = treeLayerNodes.at(i)
    #     idval = node.firstChildElement("id").text()
    #     if idval in map_layers:
    #         self.iface.messageBar().pushMessage(
    #                 u"Map already consists layer ID",
    #                 u"", 
    #                 duration=5,
    #                 level=2
    #             )
    #         raise Exception("Map already consists layer ID " + idval)

layerTreeElem = doc.documentElement().firstChildElement( "layer-tree-group" )
    loadInLegend = True
    if layerTreeElem is not None:
        root.readChildrenFromXml( layerTreeElem, context )
        loadInLegend = False

layers = QgsLayerDefinition.loadLayerDefinitionLayers( doc, context )
    project.addMapLayers(layers, loadInLegend)

for layer in layers:
        layer.resolveReferences(project)
    root.resolveReferences(project)

nodes = root.children()
    for idx, n in enumerate(nodes):
        root.takeChild(n)
    rootGroup.insertChildNodes(0, nodes)

return True

Kadir Şahbaz · Answer

Use QgsLayerDefinition.loadLayerDefinitionLayers.
Documentation:

QgsLayerDefinition::loadLayerDefinitionLayers(QDomDocument & document,
                                              QgsReadWriteContext & context)

Creates new layers from a layer definition document.
This is a low-level routine that does not resolve layer ID conflicts,
dependencies and joins

Therefore you should use loadLayerDefinitionLayers instead of loadLayerDefinition so that you don't need to change ids.
layer_list = QgsLayerDefinition().loadLayerDefinitionLayers(path)
QgsProject.instance().addMapLayers(layer_list)

Changing layer id in QGIS

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