FilterAndBrowseModel QML Type

The FilterAndBrowseModel is a generic model which can be used to search, browse, filter and sort data. More...

Import Statement: import QtInterfaceFramework 1.0
Instantiates: QIfFilterAndBrowseModel
Inherits:

PagingModel

Properties

Methods

Detailed Description

The FilterAndBrowseModel should be used directly or as a base class whenever a lot of data needs to be presented in a ListView.

The model is built upon the basic principle of filtering and sorting the data already where they are created instead of retrieving everything and sort or filter it locally. In addition the FilterAndBrowseModel only fetches the data it really needs and can it can be configured how this can be done.

All rows in the model need to be subclassed from StandardItem.

The following roles are available in this model:

Role nameTypeDescription
namestringThe name of the item. E.g. The name of a contact in a addressbook, or the artist-name in a list of artists.
typestringThe type of the item. E.g. "artist", "track", "contact".
itemobjectThe item itself. This provides access to the properties which are type specific. E.g. the address of a contact.
canGoForwardboolTrue if this item can be used to go one level forward and display the next set of items.

Setting it up

The FilterAndBrowseModel is using QtInterfaceFramework's Dynamic Backend System and is derived from QIfAbstractFeatureListModel. Other than most "QtInterfaceFramework Feature classes", the FilterAndBrowseModel doesn't automatically connect to available backends.

The easiest approach to set it up, is to connect to the same backend used by another feature. E.g. for connecting to the media backend, use the instance from the mediaplayer feature:

Item {
    MediaPlayer {
        id: player
    }

    FilterAndBrowseModel {
        serviceObject: player.serviceObject
    }
}

Content Types

Once the model is connected to a backend, the contentType needs to be selected. All possible content types can be queried from the availableContentTypes property. As the name already suggests, this property selects what type of content should be shown in the model. For the mediaplayer example, the available content types could be "track", "album" and "artist".

Filtering and Sorting

One of the main use case of the FilterAndBrowseModel is to provide a powerful way of filtering and sorting the content of the underlying data model. As explained above, the filtering and sorting is supposed to happen where the data is produced. To make this work across multiple backends the Qt Interface Framework Query Language was invented.

The query property is used to sort the content of the model: e.g. by setting the string "[/name]", the content will be sorted by name in ascending order.

For filtering, the same property is used but without the brackets e.g. "name='Example Item'" for only showing items which have the 'name' property set to 'Example Item'.

Filtering and sorting can also be combined in one string and the filter part can also be more complex. More on that can be found in the detailed Qt Interface Framework Query Language Documentation.

Browsing

In addition to filtering and sorting, the FilterAndBrowseModel also supports browsing through a hierarchy of different content types. The easiest way to explain this is to look at the existing media example.

When implementing a library view of all available media files, you might want to provide a way for the user to browse through the media database and select a song. You might also want to provide several staring points and from there limit the results. E.g.

  • Artist -> Album -> Track
  • Album -> Track
  • Track

This can be achieved by defining a complex filter query which takes the previously selected item into account. That is the most powerful way of doing it, as the developer/designer can define the browsing order and it can easily be changed. The downside of this is that the backend needs to support this way of filtering and sorting as well, which is not always be the case. A good example here is a DLNA backend, where the server already defines a fixed browsing order.

The FilterAndBrowseModel provides the following methods/properties for browsing:

The FilterAndBrowseModel supports two navigation types when browsing through the available data: for most use cases the simple InModelNavigation type is sufficient. By using this, the content type of the current model instance changes when navigating and the model is reset to show the new data. The other navigation type is OutOfModelNavigation and leaves the current model instance as it is. Instead the goForward() method returns a new model instance which contains the new data. This is especially useful when several views need to be open at the same time. E.g. when used inside a QML StackView.

StackView {
    id: stack
    initialItem: view

    Component {
        id: view
        ListView {
            model: FilterAndBrowseModel {
                contentType: "artist"
            }
            delegate: MouseArea {
                onClicked: {
                    stack.push({ "item" : view,
                                "properties:" {
                                    "model" : model->goForward(index, FilterAndBrowseModel.OutOfModelNavigation)
                                }});
                }
            }
        }
    }
}

Note: Please also see the PagingModel documentation for how the data loading works and the Models section for more information about all models in QtInterfaceFramework.

See also goForward().

Property Documentation

availableContentTypes : list<string>

Holds all the available content types

See also contentType.


canGoBack : bool

Holds whether the goBack() function can be used to return to the previous content.

See Browsing for more information.


contentType : string

Holds the current type of content displayed in this model.

Note: When changing this property the content will be reset.

See also FilterAndBrowseModel::availableContentTypes.


query : string

Holds the current query used for filtering and sorting the current content of the model.

Note: When changing this property the content will be reset.

See Qt Interface Framework Query Language for more information.

See also FilteringAndSorting.


Method Documentation

bool canGoForward(i)

Returns true when the item at index i can be used to show the next set of elements.

See also Browsing for more information.


void goBack()

Goes one level back in the navigation history.

See also Browsing for more information.


FilterAndBrowseModel goForward(i, navigationType)

Uses the item at index i and shows the next set of items.

navigationType can be one of the following values:

ConstantDescription
InModelNavigationThe new content will be loaded into this model and the existing model data will be reset
OutOfModelNavigationA new model will be returned which loads the new content. The model data of this model will not be changed and can still be used.

Note: Whether the OutOfModelNavigation navigation type is supported is decided by the backend.

See also Browsing for more information.


indexOf(StandardItem item)

Determines the index of item in this model.

The result is returned as a PendingReply.


insert(int index, StandardItem item)

Insert the item at the position index.

If the backend doesn't accept the provided item, this operation will end in a no op.

The returned PendingReply notifies about when the action has been done or whether it failed.


move(int cur_index, int new_index)

Moves the item at position cur_index to the new position new_index.

The returned PendingReply notifies about when the action has been done or whether it failed.


remove(int index)

Removes the item at position index.

The returned PendingReply notifies about when the action has been done or whether it failed.


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