Synchronizing QGIS Print Composer with map view?

Question

I want to create a template using the "Print Composer" from my layers loaded in QGIS 2.18.7 (Las Palmas). The problem is that it seems the map element is not "synchronized" with the map view. For instance, if I zoom-in on the map view, I want the map element on the template also being automatically updated with the zoom.

Another problem related to this is that I don't know how to display the selected features in the template:

Is there any way of updating the map template automatically?

Answer 1

With a little help from Python, we could create a function which refreshes your composer map each time the canvas extent (from the main window) has changed. In otherwords, whenever you pan or zoom in/out of the canvas, the composer map will also update. You can type the following code into the Python Console:

def update_composer():
    active_Composer = iface.activeComposers()
    canvas = iface.mapCanvas()
    composer = active_Composer[0]
    composition = composer.composition()
    maps = [item for item in composition.items() if item.type() == QgsComposerItem.ComposerMap and item.scene()]
    composer_map = maps[0]
    moveX = composer_map.extent().center().x()-canvas.extent().center().x()
    moveY = composer_map.extent().center().y()-canvas.extent().center().y()
    unitCon = composer_map.mapUnitsToMM()
    composer_map.moveContent(-moveX * unitCon, moveY * unitCon)
    composer_map.setNewScale(canvas.scale())

iface.mapCanvas().extentsChanged.connect(update_composer)

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Credit to the author Ed B for his plugin: Sync Composer With Map of which this code was based upon (you can download/install this plugin from the menubar: Plugins > Manage and Install Plugins...).

Answer 2

I try this solution:

def print_image(self):
    layers = QgsMapLayerRegistry.instance().mapLayers()
    """select layer by name"""
    for name, layer in layers.iteritems():
        if(layer.name()=="[YOUR LAYER NAME]"):

            lay=layer
    self.iface.mapCanvas().zoomToSelected( lay )
    self.iface.mapCanvas().refresh()
    path = 'C:\new folder\image.png'
    self.iface.mapCanvas().saveAsImage(path)

This makes a photo of the map view and I get the selected objects

Answer 3

I have finally used this solution:

In layer Properties->Style->Rule-based

With $id=$atlasfeatureid I can see the items selected by the atlas

Answer 4

In the "Layers" section you just need to thick the "Follow map theme" option and your current view from QGIS should have to come out.