<div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial"><div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial"><div>hello,<br>When I first loaded a map,I want to display a part of map,I used Qgsmapcanvas.setextent(),<br>But the map didn't change. <span id="result_box" class="short_text" lang="en"><span class="">The following code:<br>    QgsMapLayer* Layer = new QgsRasterLayer("Resources/mapdata/zgc.tif", "gdal", false);<br>    if (!Layer->isValid())<br>    {<br>        //QMessageBox::critical(this, "error", "layer is invalid");<br>        return;<br>    }<br>    QgsMapLayerRegistry::instance()->addMapLayer(Layer);<br>    mapCanvasLayerSet.append(Layer);<br>    mapCanvas->setLayerSet(mapCanvasLayerSet);<br>    mapCanvas->setVisible(true);<br>    QgsCoordinateReferenceSystem wgs84(4326, QgsCoordinateReferenceSystem::EpsgCrsId);<br>    QgsCoordinateReferenceSystem web(3857, QgsCoordinateReferenceSystem::EpsgCrsId);<br>    mapCanvas->setDestinationCrs(wgs84);  <br>    mapCanvas->setDestinationCrs(web); <br>    mapCanvas->setCrsTransformEnabled(true);<br><br>    QgsRectangle r(0, 0, 800, 800);<br>    mapCanvas->setExtent(r,true);<br><br>    mapCanvas->setCachingEnabled(true);<br>    mapCanvas->refresh();<br>How to use setextent,and how to display a part of map,Can you tell me ?<br>Thanks for help!!<br>Li<br></span></span></div></div></div><br><br><span title="neteasefooter"><p> </p></span>