Loader QML Type

This property is true if the Loader is currently active. The default value for this property is true.

If the Loader is inactive, changing the source or sourceComponent will not cause the item to be instantiated until the Loader is made active.

Setting the value to inactive will cause any item loaded by the loader to be released, but will not affect the source or sourceComponent.

The status of an inactive loader is always Null.

See also source and sourceComponent.

This property holds whether the component will be instantiated asynchronously. By default it is false.

When used in conjunction with the source property, loading and compilation will also be performed in a background thread.

Loading asynchronously creates the objects declared by the component across multiple frames, and reduces the likelihood of glitches in animation. When loading asynchronously the status will change to Loader.Loading. Once the entire component has been created, the item will be available and the status will change to Loader.Ready.

Changing the value of this property to false while an asynchronous load is in progress will force immediate, synchronous completion. This allows beginning an asynchronous load and then forcing completion if the Loader content must be accessed before the asynchronous load has completed.

To avoid seeing the items loading progressively set visible appropriately, e.g.

Loader {
    source: "mycomponent.qml"
    asynchronous: true
    visible: status == Loader.Ready
}

Note that this property affects object instantiation only; it is unrelated to loading a component asynchronously via a network.

This property holds the top-level object that is currently loaded.

Since QtQuick 2.0, Loader can load any object type.

This property holds the progress of loading QML data from the network, from 0.0 (nothing loaded) to 1.0 (finished). Most QML files are quite small, so this value will rapidly change from 0 to 1.

See also status.

This property holds the URL of the QML component to instantiate.

Since QtQuick 2.0, Loader is able to load any type of object; it is not restricted to Item types.

To unload the currently loaded object, set this property to an empty string, or set sourceComponent to undefined. Setting source to a new URL will also cause the item created by the previous URL to be unloaded.

See also sourceComponent, status, and progress.

This property holds the Component to instantiate.

Item {
    Component {
        id: redSquare
        Rectangle { color: "red"; width: 10; height: 10 }
    }

    Loader { sourceComponent: redSquare }
    Loader { sourceComponent: redSquare; x: 10 }
}

To unload the currently loaded object, set this property to undefined.

Since QtQuick 2.0, Loader is able to load any type of object; it is not restricted to Item types.

See also source and progress.

This property holds the status of QML loading. It can be one of:

• Loader.Null - the loader is inactive or no QML source has been set
• Loader.Ready - the QML source has been loaded
• Loader.Loading - the QML source is currently being loaded
• Loader.Error - an error occurred while loading the QML source

Use this status to provide an update or respond to the status change in some way. For example, you could:

• Trigger a state change:

  State { name: 'loaded'; when: loader.status == Loader.Ready }

• Implement an onStatusChanged signal handler:

  Loader {
      id: loader
      onStatusChanged: if (loader.status == Loader.Ready) console.log('Loaded')
  }

• Bind to the status value:

  Text { text: loader.status == Loader.Ready ? 'Loaded' : 'Not loaded' }

Note that if the source is a local file, the status will initially be Ready (or Error). While there will be no onStatusChanged signal in that case, the onLoaded will still be invoked.

See also progress.

This signal is emitted when the status becomes Loader.Ready, or on successful initial load.

Note: The corresponding handler is onLoaded.

Creates an object instance of the given source component that will have the given properties. The properties argument is optional. The instance will be accessible via the item property once loading and instantiation is complete.

If the active property is false at the time when this function is called, the given source component will not be loaded but the source and initial properties will be cached. When the loader is made active, an instance of the source component will be created with the initial properties set.

Setting the initial property values of an instance of a component in this manner will not trigger any associated Behaviors.

Note that the cached properties will be cleared if the source or sourceComponent is changed after calling this function but prior to setting the loader active.

Example:

// ExampleComponent.qml
import QtQuick 2.0
Rectangle {
    id: rect
    color: "red"
    width: 10
    height: 10

    Behavior on color {
        NumberAnimation {
            target: rect
            property: "width"
            to: (rect.width   20)
            duration: 0
        }
    }
}

// example.qml
import QtQuick 2.0
Item {
    Loader {
        id: squareLoader
        onLoaded: console.log(squareLoader.item.width);
        // prints [10], not [30]
    }

    Component.onCompleted: {
        squareLoader.setSource("ExampleComponent.qml",
                             { "color": "blue" });
        // will trigger the onLoaded code when complete.
    }
}

See also source and active.