接下來我們來新增線要素,其實畫點畫線的方法有好多種,這裡我就介紹一種,不多說了,我們來看程式碼:
``#include "mainwindow.h"

include "ui_mainwindow.h"

include <qgsmapcanvas.h>

include <qgsvectorlayer.h>

include

include <qgssymbol.h>

include <qgssymbollayer.h>

include <qgsvectordataprovider.h>

MainWindow::MainWindow(QWidget *parent)

QMainWindow(parent)

{
//老規矩我們來建立畫布
QgsMapCanvas *canvas = new QgsMapCanvas(this);
//新增一個背景向量圖層
QString path = "D:/Qt/bbb.shp";
QgsVectorLayer *layer = new QgsVectorLayer(path,"MyPoint","ogr");

//在這裡缺少一步<建立連結串列>,我把QList<QgsMapLayer *>Layers設定成全域性變數
//這個是線要素的新增方法,我們跳進函式來看一下
AddLine();
//將向量層追加到連結串列中
Layers.append(layer);

//設定畫布縮放
canvas->setLayers(layers);
canvas->zoomToFullExtent();
//設定畫布背景顏色,當然這個可以根據你自己的需求來設定
canvas->setCanvasColor(QColor(124,134,205));

//設定畫布為當前中心視窗
this->setCentralWidget(canvas);
 

}

MainWindow::~MainWindow()
{

}void MainWindow::AddLine()
{
// 建立一個線圖層。
QgsVectorLayer *Line_Layer = new QgsVectorLayer("LineString?crs=epsg:4326","MyLine","memory");
QgsVectorDataProvider *dataProder =Line_Layer->dataProvider();
//在指定座標新增點
QgsFeature feature;
QgsGeometry geometry = QgsGeometry::fromPointXY(QgsPointXY(50,50));
//通過點座標進行畫線
QgsPolyline line ;
line << QgsPoint(100.4443,32.2123) << QgsPoint(130.5557,50.4445);
geometry =QgsGeometry::fromPolyline(line);
feature.setGeometry( geometry );
dataProder->addFeatures(QgsFeatureList()<< feature);
Line_Layer->updateExtents();
//將線圖層載入到連結串列中
layers.append(Line_Layer);
}``

實現如下圖:

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