Build a legend

View inC++QMLView on GitHubSample viewer app

Build a legend for all the operational layers in the map.

screenshot

Use case

Legends are used to describe what each symbol on a map represents. A common format is to show an image of the symbol alongside of a text description of what that symbol represents. This sample demonstrates how a simple legend can be built up in code using the LayerContent interface.

How to use the sample

  1. Open the sample
  2. Flick through the legend control to see the various elements that represent features on the map.

How it works

  1. Layers implement the LayerContent interface, which contain a list of LegendInfo. LegendInfo contains a Symbol and a name string. Layer.autoFetchLegendInfos must be called on each Layer instance to fetch the info from the data.
  2. All of the resulting LegendInfo objects are passed into the LegendInfoListModel.
  3. A QML ListView directly consumes this model, and separates each item by using a section.

Relevant API

  • Layer.autoFetchLegendInfos
  • LayerContent
  • LegendInfo
  • LegendInfoListModel

Tags

legend, legend info, symbol swatch, toolkit

Sample Code

BuildLegend.qml
Use dark colors for code blocksCopy
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
// [WriteFile Name=BuildLegend, 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]

import QtQuick
import QtQuick.Controls
import Esri.ArcGISRuntime

Rectangle {
    width: 800
    height: 600

    // Create the MapView
    MapView {
        anchors.fill: parent

        Component.onCompleted: {
            // Set the focus on MapView to initially enable keyboard navigation
            forceActiveFocus();
        }

        // Nest the Map as a child of the MapView
        Map {
            id: map
            // automatically fetch the legend infos for all operational layers
            autoFetchLegendInfos: true

            // Nest the Basemap to add it as the Map's Basemap
            Basemap {
                initStyle: Enums.BasemapStyleArcGISTopographic
            }

            // Add a map image layer as an operational layer
            ArcGISMapImageLayer {
                id: mapImageLayer
                url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Census/MapServer"
            }

            // Add a feature layer as an operational layer
            FeatureLayer {
                id: featureLayer
                featureTable: ServiceFeatureTable {
                    url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/Recreation/FeatureServer/0"
                }
            }

            // Set the initial viewpoint
            initialViewpoint: ViewpointCenter {
                center: Point {
                    x: -11e6
                    y: 6e6
                    spatialReference: SpatialReference {wkid: 102100}
                }
                targetScale: 9e7
            }
        }
    }

    // Create outter rectangle for the legend
    Rectangle {
        id: legendRect
        anchors {
            margins: 10
            left: parent.left
            top: parent.top
        }
        property bool expanded: true
        height: 200
        width: 175
        color: "lightgrey"
        opacity: 0.95
        radius: 10
        clip: true
        border {
            color: "darkgrey"
            width: 1
        }

        // Animate the expand and collapse of the legend
        Behavior on height {
            SpringAnimation {
                spring: 3
                damping: .4
            }
        }

        // Catch mouse signals so they don't propagate to the map
        MouseArea {
            anchors.fill: parent
            onClicked: mouse => mouse.accepted = true
            onWheel: wheel => wheel.accepted = true
        }

        // Create UI for the user to select the layer to display
        Column {
            anchors {
                fill: parent
                margins: 10
            }
            spacing: 2

            Row {
                spacing: 55

                Text {
                    text: qsTr("Legend")
                    font {
                        pixelSize: 18
                        bold: true
                    }
                }

                // Legend icon to allow expanding and collapsing
                Image {
                    source: legendRect.expanded ? "qrc:/Samples/DisplayInformation/BuildLegend/ic_menu_legendpopover_light_d.png" : "qrc:/Samples/DisplayInformation/BuildLegend/ic_menu_legendpopover_light.png"
                    width: 28
                    height: width

                    MouseArea {
                        anchors.fill: parent
                        onClicked: {
                            if (legendRect.expanded) {
                                legendRect.height = 40;
                                legendRect.expanded = false;
                            } else {
                                legendRect.height = 200;
                                legendRect.expanded = true;
                            }
                        }
                    }
                }
            }

            // Create a list view to display the legend
            ListView {
                id: legendListView
                anchors.margins: 10
                width: 165
                height: 150
                clip: true
                model: map.legendInfos

                // Create delegate to display the name with an image
                delegate: Item {
                    width: parent ? parent.width : 0
                    height: 35
                    clip: true

                    Row {
                        spacing: 5
                        anchors.verticalCenter: parent.verticalCenter

                        Image {
                            anchors.verticalCenter: parent.verticalCenter
                            width: 24
                            height: width
                            source: symbolUrl
                        }
                        Text {
                            anchors.verticalCenter: parent.verticalCenter
                            width: 125
                            text: name
                            wrapMode: Text.WordWrap
                            font.pixelSize: 12
                        }
                    }
                }

                section {
                    property: "layerName"
                    criteria: ViewSection.FullString
                    labelPositioning: ViewSection.CurrentLabelAtStart | ViewSection.InlineLabels
                    delegate: Rectangle {
                        width: 180
                        height: childrenRect.height
                        color: "lightsteelblue"

                        Text {
                            text: section
                            font.bold: true
                            font.pixelSize: 13
                        }
                    }
                }
            }
        }
    }
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.