WheelHandler QML 类型

用于鼠标滚轮的处理程序。 更多...

import 语句：	import QtQuick 2.15
继承：	SinglePointHandler

• 所有成员列表，包括继承成员

特性

• acceptedButtons : flags
• acceptedDevices : flags
• acceptedModifiers : flags
• acceptedPointerTypes : flags
• active : bool
• activeTimeout : real
• cursorShape : Qt::CursorShape
• dragThreshold : int
• enabled : bool
• grabPermissions : flags
• invertible : bool
• margin : real
• orientation : enum
• parent : Item
• point : HandlerPoint
• property : string
• rotation : real
• rotationScale : real
• target : Item
• targetScaleMultiplier : real
• targetTransformAroundCursor : bool

信号

• canceled (EventPoint point )
• grabChanged (GrabTransition transition , EventPoint point )
• wheel (PointerScrollEvent event )

详细描述

WheelHandler is a handler that is used to interactively manipulate some numeric property of an Item as the user rotates the mouse wheel. Like other Input Handlers, by default it manipulates its target . Declare property to control which target property will be manipulated:

import QtQuick 2.14
Rectangle {
    width: 170; height: 120
    color: "green"; antialiasing: true
    WheelHandler {
        property: "rotation"
        onWheel: console.log("rotation", event.angleDelta.y,
                             "scaled", rotation, "@", point.position, "=>", parent.rotation)
    }
}
					

BoundaryRule is quite useful in combination with WheelHandler (as well as with other Input Handlers) to declare the allowed range of values that the target property can have. For example it is possible to implement scrolling using a combination of WheelHandler and DragHandler to manipulate the scrollable Item's y property when the user rotates the wheel or drags the item on a touchscreen, and BoundaryRule to limit the range of motion from the top to the bottom:

import QtQuick 2.14
import Qt.labs.animation 1.0
Item {
    width: 320; height: 480
    Flow {
        id: content
        width: parent.width
        spacing: 2; padding: 2
        WheelHandler {
            orientation: Qt.Vertical
            property: "y"
            rotationScale: 15
            acceptedDevices: PointerDevice.Mouse | PointerDevice.TouchPad
            onActiveChanged: if (!active) ybr.returnToBounds()
        }
        DragHandler {
            xAxis.enabled: false
            onActiveChanged: if (!active) ybr.returnToBounds()
        }
        BoundaryRule on y {
            id: ybr
            minimum: content.parent.height - content.height
            maximum: 0
            minimumOvershoot: 400; maximumOvershoot: 400
            overshootFilter: BoundaryRule.Peak
        }
        Repeater {
            model: 1000
            Rectangle { color: "gray"; width: 10 + Math.random() * 100; height: 15 }
        }
    }
}
					

Alternatively, if property is not set or target is null, WheelHandler will not automatically manipulate anything; but the rotation property can be used in a binding to manipulate another property, or you can implement onWheel and handle the wheel event directly.

WheelHandler handles only a rotating mouse wheel by default. Optionally it can handle smooth-scrolling events from touchpad gestures, by setting acceptedDevices to PointerDevice.Mouse | PointerDevice.TouchPad .

注意： Some non-mouse hardware (such as a touch-sensitive Wacom tablet, or a Linux laptop touchpad) generates real wheel events from gestures. WheelHandler will respond to those events as wheel events regardless of the setting of the acceptedDevices 特性。

另请参阅 MouseArea and Flickable .

特性文档编制

acceptedButtons : flags

The mouse buttons which can activate this Pointer Handler.

默认情况下，此特性被设为 Qt.LeftButton . It can be set to an OR combination of mouse buttons, and will ignore events from other buttons.

For example, a control could be made to respond to left and right clicks in different ways, with two handlers:

Item {
    TapHandler {
        onTapped: console.log("left clicked")
    }
    TapHandler {
        acceptedButtons: Qt.RightButton
        onTapped: console.log("right clicked")
    }
}
					

注意： Tapping on a touchscreen or tapping the stylus on a graphics tablet emulates clicking the left mouse button. This behavior can be altered via acceptedDevices or acceptedPointerTypes .

acceptedDevices : flags

The types of pointing devices that can activate this Pointer Handler.

默认情况下，此特性被设为 PointerDevice.AllDevices . If you set it to an OR combination of device types, it will ignore events from non-matching devices.

For example, a control could be made to respond to mouse and stylus clicks in one way, and touchscreen taps in another way, with two handlers:

Item {
   TapHandler {
       acceptedDevices: PointerDevice.Mouse | PointerDevice.Stylus
       onTapped: console.log("clicked")
   }
   TapHandler {
       acceptedDevices: PointerDevice.TouchScreen
       onTapped: console.log("tapped")
   }
}
					

acceptedModifiers : flags

If this property is set, it will require the given keyboard modifiers to be pressed in order to react to pointer events, and otherwise ignore them.

If this property is set to Qt.KeyboardModifierMask (the default value), then the PointerHandler ignores the modifier keys.

For example, an Item could have two handlers of the same type, one of which is enabled only if the required keyboard modifiers are pressed:

Item {
   TapHandler {
       acceptedModifiers: Qt.ControlModifier
       onTapped: console.log("control-tapped")
   }
   TapHandler {
       acceptedModifiers: Qt.NoModifier
       onTapped: console.log("tapped")
   }
}
					

若设置 acceptedModifiers to an OR combination of modifier keys, it means all of those modifiers must be pressed to activate the handler:

Item {
   TapHandler {
       acceptedModifiers: Qt.ControlModifier | Qt.AltModifier | Qt.ShiftModifier
       onTapped: console.log("control-alt-shift-tapped")
   }
}
					

The available modifiers are as follows:

常量	描述
NoModifier	No modifier key is allowed.
ShiftModifier	A Shift key on the keyboard must be pressed.
ControlModifier	A Ctrl key on the keyboard must be pressed.
AltModifier	An Alt key on the keyboard must be pressed.
MetaModifier	A Meta key on the keyboard must be pressed.
KeypadModifier	A keypad button must be pressed.
GroupSwitchModifier	X11 only (unless activated on Windows by a command line argument). A Mode_switch key on the keyboard must be pressed.
KeyboardModifierMask	The handler does not care which modifiers are pressed.

If you need even more complex behavior than can be achieved with combinations of multiple handlers with multiple modifier flags, you can check the modifiers in JavaScript code:

Item {
    TapHandler {
        onTapped:
            switch (point.modifiers) {
            case Qt.ControlModifier | Qt.AltModifier:
                console.log("CTRL+ALT");
                break;
            case Qt.ControlModifier | Qt.AltModifier | Qt.MetaModifier:
                console.log("CTRL+META+ALT");
                break;
            default:
                console.log("other modifiers", point.modifiers);
                break;
            }
    }
}
					

另请参阅 Qt::KeyboardModifier .

acceptedPointerTypes : flags

The types of pointing instruments (finger, stylus, eraser, etc.) that can activate this Pointer Handler.

默认情况下，此特性被设为 PointerDevice.AllPointerTypes . If you set it to an OR combination of device types, it will ignore events from non-matching events.

For example, a control could be made to respond to mouse, touch, and stylus clicks in some way, but delete itself if tapped with an eraser tool on a graphics tablet, with two handlers:

Rectangle {
   id: rect
   TapHandler {
       acceptedPointerTypes: PointerDevice.GenericPointer | PointerDevice.Finger | PointerDevice.Pen
       onTapped: console.log("clicked")
   }
   TapHandler {
       acceptedPointerTypes: PointerDevice.Eraser
       onTapped: rect.destroy()
   }
}
					

[read-only] active : bool

This holds true whenever this Input Handler has taken sole responsibility for handing one or more EventPoints, by successfully taking an exclusive grab of those points. This means that it is keeping its properties up-to-date according to the movements of those Event Points and actively manipulating its target (if any).

activeTimeout : real

The amount of time in seconds after which the active property will revert to false if no more wheel events are received. The default is 0.1 (100 ms).

当 WheelHandler handles events that contain scroll phase information, such as events from some touchpads, the active property will become false as soon as an event with phase Qt::ScrollEnd is received; in that case the timeout is not necessary. But a conventional mouse with a wheel does not provide the scroll phase: the mouse cannot detect when the user has decided to stop scrolling, so the active property transitions to false after this much time has elapsed.

cursorShape : Qt::CursorShape

This property holds the cursor shape that will appear whenever the mouse is hovering over the parentItem while active is true .

The available cursor shapes are:

• Qt.ArrowCursor
• Qt.UpArrowCursor
• Qt.CrossCursor
• Qt.WaitCursor
• Qt.IBeamCursor
• Qt.SizeVerCursor
• Qt.SizeHorCursor
• Qt.SizeBDiagCursor
• Qt.SizeFDiagCursor
• Qt.SizeAllCursor
• Qt.BlankCursor
• Qt.SplitVCursor
• Qt.SplitHCursor
• Qt.PointingHandCursor
• Qt.ForbiddenCursor
• Qt.WhatsThisCursor
• Qt.BusyCursor
• Qt.OpenHandCursor
• Qt.ClosedHandCursor
• Qt.DragCopyCursor
• Qt.DragMoveCursor
• Qt.DragLinkCursor

The default value is not set, which allows the cursor of parentItem to appear. This property can be reset to the same initial condition by setting it to undefined.

注意： When this property has not been set, or has been set to undefined , if you read the value it will return Qt.ArrowCursor .

该特性在 Qt 5.15 引入。

另请参阅 Qt::CursorShape , QQuickItem::cursor() ，和 HoverHandler::cursorShape .

dragThreshold : int

The distance in pixels that the user must drag an event point in order to have it treated as a drag gesture.

The default value depends on the platform and screen resolution. It can be reset back to the default value by setting it to undefined. The behavior when a drag gesture begins varies in different handlers.

该特性在 Qt 5.15 引入。

enabled : bool

若 PointerHandler is disabled, it will reject all events and no signals will be emitted.

grabPermissions : flags

This property specifies the permissions when this handler's logic decides to take over the exclusive grab, or when it is asked to approve grab takeover or cancellation by another handler.

常量	描述
PointerHandler.TakeOverForbidden	This handler neither takes from nor gives grab permission to any type of Item or Handler.
PointerHandler.CanTakeOverFromHandlersOfSameType	This handler can take the exclusive grab from another handler of the same class.
PointerHandler.CanTakeOverFromHandlersOfDifferentType	This handler can take the exclusive grab from any kind of handler.
PointerHandler.CanTakeOverFromItems	This handler can take the exclusive grab from any type of Item.
PointerHandler.CanTakeOverFromAnything	This handler can take the exclusive grab from any type of Item or Handler.
PointerHandler.ApprovesTakeOverByHandlersOfSameType	This handler gives permission for another handler of the same class to take the grab.
PointerHandler.ApprovesTakeOverByHandlersOfDifferentType	This handler gives permission for any kind of handler to take the grab.
PointerHandler.ApprovesTakeOverByItems	This handler gives permission for any kind of Item to take the grab.
PointerHandler.ApprovesCancellation	This handler will allow its grab to be set to null.
PointerHandler.ApprovesTakeOverByAnything	This handler gives permission for any any type of Item or Handler to take the grab.

默认为 PointerHandler.CanTakeOverFromItems | PointerHandler.CanTakeOverFromHandlersOfDifferentType | PointerHandler.ApprovesTakeOverByAnything which allows most takeover scenarios but avoids e.g. two PinchHandlers fighting over the same touchpoints.

invertible : bool

Whether or not to reverse the direction of property change if QQuickPointerScrollEvent::inverted is true. The default is true .

If the operating system has a "natural scrolling" setting that causes scrolling to be in the same direction as the finger movement, then if this property is set to true ，和 WheelHandler is directly setting a property on target , the direction of movement will correspond to the system setting. If this property is set to false , it will invert the rotation so that the direction of motion is always the same as the direction of finger movement.

margin : real

The margin beyond the bounds of the parent item within which an event point can activate this handler. For example, on a PinchHandler 在哪里 target is also the parent , it's useful to set this to a distance at least half the width of a typical user's finger, so that if the parent has been scaled down to a very small size, the pinch gesture is still possible. Or, if a TapHandler -based button is placed near the screen edge, it can be used to comply with Fitts's Law: react to mouse clicks at the screen edge even though the button is visually spaced away from the edge by a few pixels.

默认值为 0。