Render features in a layer using a distinct symbol for each unique attribute value.
Use case
A unique value renderer allows you to symbolize features in a layer based on one or more matching attributes. This is typically done by using unique colors, fill styles, or images to represent features with equal values in a string field. A unique value renderer could be used to show different types of trees on a vegetation map by using a symbols corresponding to matching name attributes.
How to use the sample
The map with the symbolized feature layer will be shown automatically when the sample loads.
How it works
This sample demonstrates how to use a UniqueValueRenderer to style different features in a FeatureLayer. Using the UniqueValueRenderer allows for separate symbols to be used for features that have a specific value in a certain field. In this case, the field is state abbreviations in the USA. Multiple fields can be used; this sample only uses one:
- Multiple
SimpleFillSymbolss are defined for each type of feature we want to render differently. SimpleFillSymbols can be applied to polygon features, which is the type of feature used for thisServiceFeatureTable.- Separate
UniqueValues objects are created which define the values in the renderer field and what symbol should be used to render matching features. - A default symbol is created to render all features that do not match the
UniqueValues defined.
Relevant API
- FeatureLayer
- ServiceFeatureTable
- SimpleFillSymbol
- SimpleLineSymbol
- UniqueValue
- UniqueValueRenderer
About the data
The map shows U.S. states symbolized by subregion. Symbols are defined for Pacific, Mountain, and West South Central states. All other features are symbolized with the default symbol.
Tags
draw, renderer, symbol, symbology, values
Sample Code
// [WriteFile Name=Unique_Value_Renderer, Category=DisplayInformation]
// [Legal]
// Copyright 2016 Esri.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// [Legal]
#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD
#include "Unique_Value_Renderer.h"
#include "Map.h"
#include "MapQuickView.h"
#include "Basemap.h"
#include "ServiceFeatureTable.h"
#include "FeatureLayer.h"
#include "UniqueValueRenderer.h"
#include "SimpleFillSymbol.h"
#include "Viewpoint.h"
#include "Envelope.h"
#include "MapTypes.h"
#include "LayerListModel.h"
#include "SymbolTypes.h"
#include "UniqueValue.h"
#include "UniqueValueListModel.h"
#include "SimpleLineSymbol.h"
#include "SpatialReference.h"
#include <QUrl>
#include <QStringList>
#include <QVariantList>
using namespace Esri::ArcGISRuntime;
Unique_Value_Renderer::Unique_Value_Renderer(QQuickItem* parent) :
QQuickItem(parent)
{
}
Unique_Value_Renderer::~Unique_Value_Renderer() = default;
void Unique_Value_Renderer::init()
{
qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
qmlRegisterType<Unique_Value_Renderer>("Esri.Samples", 1, 0, "Unique_Value_RendererSample");
}
void Unique_Value_Renderer::componentComplete()
{
QQuickItem::componentComplete();
// find QML MapView component
m_mapView = findChild<MapQuickView*>("mapView");
// create a new basemap instance
Basemap* basemap = new Basemap(BasemapStyle::ArcGISTopographic, this);
// create a new map instance
m_map = new Map(basemap, this);
// create featureLayer with URL
m_featureTable = new ServiceFeatureTable(QUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer/2"), this);
m_featureLayer = new FeatureLayer(m_featureTable, this);
m_map->operationalLayers()->append(m_featureLayer);
// create unique renderer
m_uniqueValueRenderer = new UniqueValueRenderer(this);
// you can add multiple fields. In this case, only one is used
m_uniqueValueRenderer->setFieldNames(QStringList("STATE_ABBR"));
// create symbols to be used in the renderer
m_defaultSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle::Null, QColor("black"), new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("gray"), 2, this), this);
m_californiaSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle::Solid, QColor("red"), new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("red"), 2, this), this);
m_arizonaSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle::Solid, QColor("green"), new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("green"), 2, this), this);
m_nevadaSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle::Solid, QColor("blue"), new SimpleLineSymbol(SimpleLineSymbolStyle::Solid, QColor("blue"), 2, this), this);
// create unique values and add to the UniqueValueRenderer
createUniqueValue("CA", m_californiaSymbol);
createUniqueValue("AZ", m_arizonaSymbol);
createUniqueValue("NV", m_nevadaSymbol);
// set default symbol
m_uniqueValueRenderer->setDefaultSymbol(m_defaultSymbol);
// set the renderer on the feature layer
m_featureLayer->setRenderer(m_uniqueValueRenderer);
// set initial viewpoint
m_map->setInitialViewpoint(Viewpoint(Envelope(-13893029.0, 3573174.0, -12038972.0, 5309823.0, SpatialReference::webMercator())));
// set map on the map view
m_mapView->setMap(m_map);
}
void Unique_Value_Renderer::createUniqueValue(QString stateName, SimpleFillSymbol* fillSymbol)
{
// add state's attribute value for field "STATE_ABBR" to QVariantList
QVariantList stateValue;
stateValue.append(stateName);
// set value for a State to be rendered. (label, description, attribute value list, symbol, parent)
UniqueValue* uniqueValue = new UniqueValue(stateName, "The State of " + stateName, stateValue, fillSymbol, this);
// append to UniqueValueRenderer
m_uniqueValueRenderer->uniqueValues()->append(uniqueValue);
}