Qt 5.9 | Qt Location | Qt Location Examples | Places (QML)

Qt 5.9.4 Reference Documentation

# Places (QML)

The Places example demonstrates how to search for Places. In particular it shows how further information such as reviews, images and related content can be retrieved.

## Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

The example can work with any of the available geo services plugins. However, some plugins may require additional plugin parameters in order to function correctly. Plugin parameters can be passed on the command line using the `--plugin` argument, which takes the form:

      --plugin.<parameter name> <parameter value>

Refer to the documentation for each of the geo services plugins for details on what plugin parameters they support. The default plugin used by this example is Qt Location Open Street Map Plugin, which does not require any parameters.

## Overview

The Places example presents an application window displaying a map. At the top of the window is a search box, which is used to enter a place search query. To search for a place enter a search term into the text box and click the magnifying glass icon. To search for a place by category, click the category icon to display the list of available categories and select the desired category. The place search query will be for places that are near the current location shown on the map.

For some plugins like Qt Location HERE Plugin the search box provides search term suggestions when three or more characters are entered. Selecting one of the suggestions will cause a place search to be performed with the selected search text.

Clicking on a search result will display details about the place. If a places has rich content (editorials, reviews and images), these can be accessed by the buttons on the details page. To find similar places click the "Find similar" button.

The geo service provider can be changed by accessing the "Provider" menu.

## Displaying Categories

Before search by category can be performed, the list of available categories needs to be retrieved. This is achieved by creating a CategoryModel.

      CategoryModel {
          id: categoryModel
          hierarchical: true
      }

The CategoryModel type provides a model of the available categories. It can provide either a flat list or a hierarchical tree model. In this example, we use a hierarchical tree model, by setting the hierarchical property to true. The plugin property is set during example intalization.

Next we create a ListView to display the category model.

      ListView {
          id: root
          property variant categoryModel
          property variant rootIndex

          signal searchCategory(variant category)
          signal showSubcategories(variant index)

          snapMode: ListView.SnapToItem

          model: DelegateModel {
              id: delegeteDataModel
              model: root.categoryModel
              rootIndex: root.rootIndex
              delegate: CategoryDelegate {
                  onSearchCategory: root.searchCategory(category);
                  onShowSubcategories: root.showSubcategories(delegeteDataModel.modelIndex(index))
              }
          }
      }

Because a hierarchical model is being used, a DelegateModel is needed to provide navigation functionality. If flat list model was being used the view could use the CategoryModel directly.

The rootIndex property sets the root index of the DelegateModel. Categories are displayed by the CategoryDelegate, which provides two signals. The onShowSubcategories emits the showSubcategories() signal with root index to the current index causing the sub categories of the selected category to be displayed. The onSearchCategory handler emits the searchCategory() signal with a category parameter indicating which specific category has been chosen.

The CategoryDelegate displays the category name and emits the searchCategory() signal when the Label is clicked:

      Label {
          id: labelItem
          text: category.name
          anchors.left: icon.right
          anchors.verticalCenter: parent.verticalCenter
          anchors.right: arrow.left
      }

      MouseArea {
          id: mouse
          anchors.fill: parent
          onClicked: root.searchCategory()
      }

The CategoryDelegate also displays arrow ToolButton when hasModelChildren property is set.

      ToolButton {
          id: arrow
          anchors.right: parent.right
          anchors.verticalCenter: parent.verticalCenter
          anchors.rightMargin: 15
          visible: model.hasModelChildren
          iconSource: "../../resources/right.png"
          onClicked: root.showSubcategories()
      }

## Presenting Search Suggestions

The PlaceSearchSuggestionModel type is used to fetch suggested search terms based on a partially entered search term.

A new suggestion search is triggered whenever the entered search term is changed.

      SearchBar {
          id: searchBar
          onSearchTextChanged: {
              if (searchText.length >= 3 && suggestionModel != null) {
                  suggestionModel.searchTerm = searchText;
                  suggestionModel.update();
              }
          }
      }

Suggestions are only queried if the length of the search term is three or more characters.

When the status of the PlaceSearchSuggestionModel changes, search suggestions are displayed.

      PlaceSearchSuggestionModel {
          id: suggestionModel
          searchArea: searchRegion

          onStatusChanged: {
              if (status == PlaceSearchSuggestionModel.Ready)
                  stackView.showSuggestions()
          }
      }

The main object in the "SuggestionsShown" state is the ListView showing the search suggestions.

      ListView {
          id: suggestionView
          property variant suggestionModel
          signal suggestionSelected(string text)

          model: suggestionModel
          delegate: Item {
              width: parent.width
              height: label.height * 1.5
              Label {
                  id: label
                  text: suggestion
              }
              MouseArea {
                  anchors.fill: parent
                  onClicked: suggestionSelected(suggestion)
              }
          }
      }

A Label object is used as the delegate to display the suggestion text. Clicking on the suggested search term updates the search term and triggers a place search using the search suggestion.

## Searching for Places

The PlaceSearchModel type is used to search for places.

      PlaceSearchModel {
          id: placeSearchModel
          searchArea: searchRegion

          function searchForCategory(category) {
              searchTerm = "";
              categories = category;
              recommendationId = "";
              searchArea = searchRegion
              limit = -1;
              update();
          }

          function searchForText(text) {
              searchTerm = text;
              categories = null;
              recommendationId = "";
              searchArea = searchRegion
              limit = -1;
              update();
          }

          function searchForRecommendations(placeId) {
              searchTerm = "";
              categories = null;
              recommendationId = placeId;
              searchArea = null;
              limit = -1;
              update();
          }

          onStatusChanged: {
              switch (status) {
              case PlaceSearchModel.Ready:
                  if (count > 0)
                      stackView.showPlaces()
                  else
                      stackView.showMessage(qsTr("Search Place Error"),qsTr("Place not found !"))
                  break;
              case PlaceSearchModel.Error:
                  stackView.showMessage(qsTr("Search Place Error"),errorString())
                  break;
              }
          }
      }

First some of the model's properties are set, which will be used to form the search request. The searchArea property is set to the searchRegion object which is a geocircle with a center that is linked to the current location displayed on the Map.

Finally, we define three helper functions searchForCategory(), searchForText() and searchForRecommendations() which set either the categories or searchTerm or recommendationId properties and invokes the update() method to start the place search. The search results are displayed in a ListView.

      ListView {
          id: searchView
          width: parent.width
          height: parent.height

          property variant placeSearchModel
          signal showPlaceDetails(variant place, variant distance)
          signal showMap()

          model: placeSearchModel
          delegate: SearchResultDelegate {
              onShowPlaceDetails: searchView.showPlaceDetails(place, distance)
              onSearchFor: placeSearchModel.searchForText(query);
          }

          footer:

              RowLayout {
              width: parent.width

              Button {
                  text: qsTr("Previous")
                  enabled: placeSearchModel.previousPagesAvailable
                  onClicked: placeSearchModel.previousPage()
                  Layout.alignment: Qt.AlignHCenter
              }

              Button {
                  text: qsTr("Clear")
                  onClicked: {
                      placeSearchModel.reset()
                      showMap()
                  }
                  Layout.alignment: Qt.AlignHCenter
              }

              Button {
                  text: qsTr("Next")
                  enabled: placeSearchModel.nextPagesAvailable
                  onClicked: placeSearchModel.nextPage()
                  Layout.alignment: Qt.AlignHCenter
              }
          }
      }

The delegate used in the ListView, SearchResultDelegate, is designed to handle multiple search result types via a Loader object. For results of type PlaceResult the delegate is:

      Component {
          id: placeComponent
          Item {
              id: placeRoot
              width: root.width
              height: Math.max(icon.height, 3 * placeName.height)

              Rectangle {
                  anchors.fill: parent
                  color: "#44ffffff"
                  visible: mouse.pressed
              }

              Rectangle {
                  anchors.fill: parent
                  color: "#dbffde"
                  visible: model.sponsored !== undefined ? model.sponsored : false

                  Label {
                      text: qsTr("Sponsored result")
                      horizontalAlignment: Text.AlignRight
                      anchors.right: parent.right
                      anchors.bottom: parent.bottom
                      font.pixelSize: 8
                      visible: model.sponsored !== undefined ? model.sponsored : false
                  }
              }

              GridLayout {
                  rows: 2
                  columns: 2
                  anchors.fill: parent
                  anchors.leftMargin: 30
                  flow: GridLayout.TopToBottom

                  Image {
                      // anchors.verticalCenter: parent.verticalCenter
                      id:icon
                      source: place.favorite ? "../../resources/star.png" : place.icon.url()
                      Layout.rowSpan: 2
                  }

                  Label {
                      id: placeName
                      text: place.favorite ? place.favorite.name : place.name
                      Layout.fillWidth: true
                  }

                  Label {
                      id: distanceText
                      font.italic: true
                      text: Helper.formatDistance(distance)
                      Layout.fillWidth: true
                  }
              }

              Rectangle {
                  anchors.left: parent.left
                  anchors.right: parent.right
                  anchors.margins: 15
                  height: 1
                  color: "#46a2da"
              }

              MouseArea {
                  id: mouse
                  anchors.fill: parent
                  onClicked: {
                      if (model.type === undefined || type === PlaceSearchModel.PlaceResult) {
                          if (!place.detailsFetched)
                              place.getDetails();
                          root.showPlaceDetails(model.place, model.distance);
                      }
                  }
              }
          }
      }

## Displaying Place Content

Places can have additional rich content, including editorials, reviews and images. Rich content is accessed via a set of models. Content models are generally not created directly by the application developer, instead models are obtained from the editorialModel, reviewModel and imageModel properties of the Place type.

      ListView {
          id:view
          property Place place
          signal showEditorial(variant editorial)
          width: parent.width
          height: parent.height
          model: place.editorialModel
          delegate: EditorialDelegate {
              onShowEditorial: view.showEditorial(model)
          }
      }

Files:

- places/helper.js
- places/places.qml
- places/forms/Message.qml
- places/forms/MessageForm.ui.qml
- places/forms/PlaceDetails.qml
- places/forms/PlaceDetailsForm.ui.qml
- places/forms/SearchBoundingBox.qml
- places/forms/SearchBoundingBoxForm.ui.qml
- places/forms/SearchBoundingCircle.qml
- places/forms/SearchBoundingCircleForm.ui.qml
- places/forms/SearchCenter.qml
- places/forms/SearchCenterForm.ui.qml
- places/forms/SearchOptions.qml
- places/forms/SearchOptionsForm.ui.qml
- places/items/MainMenu.qml
- places/items/MapComponent.qml
- places/items/SearchBar.qml
- places/views/CategoryDelegate.qml
- places/views/CategoryView.qml
- places/views/EditorialDelegate.qml
- places/views/EditorialPage.qml
- places/views/EditorialView.qml
- places/views/ImageView.qml
- places/views/RatingView.qml
- places/views/ReviewDelegate.qml
- places/views/ReviewPage.qml
- places/views/ReviewView.qml
- places/views/SearchResultDelegate.qml
- places/views/SearchResultView.qml
- places/views/SuggestionView.qml
- places/main.cpp
- places/places.pro
- places/places.qrc