<div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial">hello,<br>When I first loaded a map,I want to display a part of map,I used Qgsmapcanvas.setextent(),<br><div>But the map didn't change. <span id="result_box" class="short_text" lang="en"><span class="">The following code:<br></span></span><br><span id="result_box" class="short_text" lang="en"><span class=""><span id="result_box" class="short_text" lang="en"><span class="">    QgsMapLayerRegistry::instance()->addMapLayer(Layer);<br>    mapCanvasLayerSet.append(Layer);<br>    mapCanvas->setLayerSet(mapCanvasLayerSet);<br>    mapCanvas->setVisible(true);<br></span></span></span></span><span id="result_box" class="short_text" lang="en"><span class=""><span id="result_box" class="short_text" lang="en"><span class=""><span id="result_box" class="short_text" lang="en"><span class="">    QgsRectangle r(0, 0, 800, 800);<br>    mapCanvas->setExtent(r,true);<br>    mapCanvas->setCachingEnabled(true);<br>    mapCanvas->refresh();<br></span></span></span></span></span></span><span id="result_box" class="short_text" lang="en"><span class="">How to use setextent,I could not understand this,and how to display a part of map,Can you tell me ?<br>Thanks for help!!<br>tong<br></span></span></div></div><br><br><span title="neteasefooter"><p> </p></span>