How To Use QML ListView: Difference between revisions

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{{Cleanup | reason=Needs to be updated to QtQuick 2}}
{{LangSwitch}}
[[Category:HowTo]]
[[Category:HowTo]]
[toc align_right="yes" depth="3"]
= How to Use QML ListView =
== Introduction ==
== Introduction ==


Line 18: Line 15:


Main.qml
Main.qml
<code>import QtQuick 1.0
<code>
import QtQuick 1.0
 
Item {
Item {
id: rootItem
  id: rootItem
// create a model item instance
  // create a model item instance
  SampleListModel {
   
id: sampleModel
  SampleListModel {
}
    id: sampleModel
  ListView {
  }
id: smapleListView
   
anchors.fill: parent
  ListView {
// concreate model
    id: sampleListView
model: sampleModel
    anchors.fill: parent
// provide delegate component.
    model: sampleModel              // concrete model
delegate: ExampleDelegate { }
    delegate: ExampleDelegate { }  // provide delegate component.
spacing: 4
    spacing: 4
}
  }
}</code>
}
</code>


Now let's code ExampleDelegate component.
Now let's code ExampleDelegate component.
Line 46: Line 46:
ExampleDelegate.qml
ExampleDelegate.qml


<code>import QtQuick 1.0
<code>
import QtQuick 1.0


Rectangle {
Rectangle {
id: delegateItem
  id: delegateItem
width: parent.width; height: 100
  width: parent.width; height: 100
color: "blue"
  color: "blue"
  Image {
   
id: imageItem
  Image {
height: parent.height; width: 100
    id: imageItem
anchors.left: parent.left
    height: parent.height; width: 100
// deligate can directly ues ListElement role name
    anchors.left: parent.left
source: imagePath
    // delegate can directly use ListElement role name
}
    source: imagePath
  Text {
  }
id: itexItem
   
anchors.left: imageItem.right
  Text {
anchors.leftMargin: 20
    id: itexItem
anchors.verticalCenter: parent.verticalCenter
    anchors.left: imageItem.right
font.pixelSize: 40
    anchors.leftMargin: 20
// deligate can direclty use ListElement role name
    anchors.verticalCenter: parent.verticalCenter
text: imageName
    font.pixelSize: 40
}
    // delegate can directly use ListElement role name
}</code>
    text: imageName
  }
}
</code>


As you can see above, '''imagePath''', and '''imageName''' are not properties of delegateItem, so where are they coming from? They are coming from the model of ListView. '''The magic is that delegate components can access roles of each ListElement it visualizes directly inside it'''.
As you can see above, '''imagePath''', and '''imageName''' are not properties of delegateItem, so where are they coming from? They are coming from the model of ListView. '''The magic is that delegate components can access roles of each ListElement it visualizes directly inside it'''.
Line 76: Line 80:
=== Example: Delegate Component Embedded in Main QML file ===
=== Example: Delegate Component Embedded in Main QML file ===


<code>import QtQuick 1.0
<code>
import QtQuick 1.0
 
Item {
Item {
id: rootItem
  id: rootItem
Component {
 
id: delegateComponent
  Component {
Item { ………. }
    id: delegateComponent
}
    Item { ... }
  ListView {
  }
// provide delegate component.
   
delegate: delegateComponent
  ListView {
}
    // provide delegate component.
}</code>
    delegate: delegateComponent
  }
}
</code>


or
or


<code>import QtQuick 1.0
<code>
import QtQuick 1.0
 
Item {
Item {
id: rootItem
  id: rootItem
ListView {
  ListView {
// provide delegate component.
    // provide delegate component.
delegate: Item {
    delegate: Item {
……………
      ...
}
    }
}
  }
}</code>
}
</code>


Now, let's create SimpleListModel model where each row has roles '''imagePath''', and '''imageName'''
Now, let's create SimpleListModel model where each row has roles '''imagePath''', and '''imageName'''
Line 114: Line 126:
Example:
Example:
  SampleListModel.qml
  SampleListModel.qml
<code>import QtQuick 1.0
<code>
import QtQuick 1.0
 
ListModel {
ListModel {
ListElement { imagePath: "1.jpg"; imageName: "flower"}
  ListElement { imagePath: "1.jpg"; imageName: "flower" }
ListElement { imagePath: "2.jpg"; imageName: "house"}
  ListElement { imagePath: "2.jpg"; imageName: "house" }
ListElement { imagePath: "3.jpg"; imageName: "water"}
  ListElement { imagePath: "3.jpg"; imageName: "water" }
}</code>
}
</code>


The above example defines a simple ListModel which can be used by a ListView. Each ListElement contains list of roles that can be directly accessed inside delegate element of ListView.
The above example defines a simple ListModel which can be used by a ListView. Each ListElement contains list of roles that can be directly accessed inside delegate element of ListView.
Line 127: Line 142:


Example :
Example :
<code>ListModel {
<code>
id: sampleModel
ListModel {
  id: sampleModel
}
}
…………..
...
sampleModel.append({"name":"sonia";"age":23})
sampleModel.append({"name":"sonia";"age":23})
</code>
</code>
Line 137: Line 153:


Example :
Example :
<code>ListModel {
<code>
id: sampleModel
ListModel {
ListElement { imagePath: "image1.jpg"; imageName:"house" }
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
}
…………..
...
 
// insert a new row to model at index 1. Index starts from 0.
// insert a new row to model at index 1. Index starts from 0.
// This is equivalent to appending at the end as index we provide is 1.
// This is equivalent to appending at the end as index we provide is 1.
sampleModel.insert(1,{"name":"sonia";"age":23})
sampleModel.insert(1, {"name":"sonia", "age":23})
</code>
</code>


Line 152: Line 170:
Example :
Example :
<code>ListModel {
<code>ListModel {
id: sampleModel
  id: sampleModel
ListElement { imagePath: "image1.jpg"; imageName:"house" }
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
}
…………..
...
// prints value of imagePath in the first row of sampleModel
// prints value of imagePath in the first row of sampleModel
console.log(sampleModel.get(0).imagePath)
console.log(sampleModel.get(0).imagePath)
Line 162: Line 180:
To Modify values of roles of a particular row, use ListModel::set(int index,jsobject dict) method
To Modify values of roles of a particular row, use ListModel::set(int index,jsobject dict) method
Example :
Example :
<code>ListModel {
<code>
id: sampleModel
ListModel {
ListElement { imagePath: "image1.jpg"; imageName:"house" }
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
}
…………..
...
sampleModel.set(0,{imagePath: "image2.jpg";imageName:"water"}
sampleModel.set(0, {imagePath: "image2.jpg", imageName:"water"})
</code>
</code>


To set value of a particular role in a given row, use ListModel::setProperty(int index, string rolename, variant value)
To set value of a particular role in a given row, use ListModel::setProperty(int index, string rolename, variant value)
Example :
Example :
<code>ListModel {
<code>
id: sampleModel
ListModel {
ListElement { imagePath: "image1.jpg"; imageName:"house" }
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
}
…………..
...
sampleModel.setProperty(0,"imagePath","image2.jpg"}
sampleModel.setProperty(0, "imagePath", "image2.jpg")
</code>
</code>



Latest revision as of 21:29, 8 July 2015

This article may require cleanup to meet the Qt Wiki's quality standards. Reason: Needs to be updated to QtQuick 2
Please improve this article if you can. Remove the {{cleanup}} tag and add this page to Updated pages list after it's clean.

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Introduction

ListView provides a way to visualize contents of an one-dimensional model. Data can come from QML model elements like ListModel, XmlListModel, or C++ custom model classes inherited from QAbstractListModel.

ListView has a model property which supplies data to be visualized, and has a delegate property which supplies how ( LAF ) each row in the model is visualized. ListView is provided as a part of model/view paradigm in Qt/Qt Quick.

ListView

ListView element needs to be told about the model to visualize and the delegate component to use to visualize each element of the model. This is done with model and delegate properties of ListView

Example

Main.qml

import QtQuick 1.0

Item {
  id: rootItem
  // create a model item instance
 
  SampleListModel {
    id: sampleModel
  }
 
  ListView {
    id: sampleListView
    anchors.fill: parent
    model: sampleModel              // concrete model
    delegate: ExampleDelegate { }   // provide delegate component.
    spacing: 4
  }
}

Now let's code ExampleDelegate component.

Delegate

Delegate components provide a way to visualize each row of model provided in ListView. An instance of delegate component is created dynamically for each row.

Example: Separate File with Delegate Component

ExampleDelegate.qml

import QtQuick 1.0

Rectangle {
  id: delegateItem
  width: parent.width; height: 100
  color: "blue"
 
  Image {
    id: imageItem
    height: parent.height; width: 100
    anchors.left: parent.left
    // delegate can directly use ListElement role name
    source: imagePath
  }
 
  Text {
    id: itexItem
    anchors.left: imageItem.right
    anchors.leftMargin: 20
    anchors.verticalCenter: parent.verticalCenter
    font.pixelSize: 40
    // delegate can directly use ListElement role name
    text: imageName
  }
}

As you can see above, imagePath, and imageName are not properties of delegateItem, so where are they coming from? They are coming from the model of ListView. The magic is that delegate components can access roles of each ListElement it visualizes directly inside it.

Alternatively, we can place this delegate component in the same .qml file where we have ListView element.

Example: Delegate Component Embedded in Main QML file

import QtQuick 1.0

Item {
  id: rootItem
  
  Component {
    id: delegateComponent
    Item { ... }
  }
 
  ListView {
    // provide delegate component.
    delegate: delegateComponent
  }
}

or

import QtQuick 1.0

Item {
  id: rootItem
  ListView {
    // provide delegate component.
    delegate: Item {
      ...
    }
  }
}

Now, let's create SimpleListModel model where each row has roles imagePath, and imageName

Different ways of providing Model data

As specified earlier, data for ListView can be provided with QML Model elements like ListModel, XmlListModel or C++ custom classes inherited from QAbstractListModel.

ListModel

ListModel provides a way to specify model data to ListView. Each row in ListModel is constructed with ListElement.

Example:

SampleListModel.qml
import QtQuick 1.0

ListModel {
  ListElement { imagePath: "1.jpg"; imageName: "flower" }
  ListElement { imagePath: "2.jpg"; imageName: "house" }
  ListElement { imagePath: "3.jpg"; imageName: "water" }
}

The above example defines a simple ListModel which can be used by a ListView. Each ListElement contains list of roles that can be directly accessed inside delegate element of ListView. Note: Copy three images with names "1.jpb","2.jpg", and "3.jpg" to folder where you have qml files.

ListModel provides methods to manipulate ListModel from JavaScript. If we start with a empty ListModel, the first item inserted in to ListModel determines the roles that will be available to delegate in ListView.

Example :

ListModel {
  id: sampleModel
}
...
sampleModel.append({"name":"sonia";"age":23})

Now, roles name, and age will be available inside delegate of ListView. If we append more rows to above model with different roles, they will not be available to delegate.

Example :

ListModel {
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
...

// insert a new row to model at index 1. Index starts from 0.
// This is equivalent to appending at the end as index we provide is 1.
sampleModel.insert(1, {"name":"sonia", "age":23})

In the above example, roles name, and age will not be available in delegate. Only roles imagePath, and imageName will be available.

To get row at a given index, use ListModel::get(index) Example :

ListModel {
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
...
// prints value of imagePath in the first row of sampleModel
console.log(sampleModel.get(0).imagePath)

To Modify values of roles of a particular row, use ListModel::set(int index,jsobject dict) method Example :

ListModel {
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
...
sampleModel.set(0, {imagePath: "image2.jpg", imageName:"water"})

To set value of a particular role in a given row, use ListModel::setProperty(int index, string rolename, variant value) Example :

ListModel {
  id: sampleModel
  ListElement { imagePath: "image1.jpg"; imageName:"house" }
}
...
sampleModel.setProperty(0, "imagePath", "image2.jpg")

To move elements inside ListModel use ListModel::move(int from, int to,int n) Moves n items from one position to another.

To remove a row from ListModel use ListModel::remove(index) and to clear all the rows in a model call ListModel.clear()