DragHandler QML Type

Handler for dragging. 更多...

import 语句：	import QtQuick 2.15
继承：	MultiPointHandler

• 所有成员列表，包括继承成员

特性

• acceptedButtons : flags
• acceptedDevices : flags
• acceptedModifiers : flags
• acceptedPointerTypes : flags
• active : bool
• cursorShape : Qt::CursorShape
• dragThreshold : int
• enabled : bool
• grabPermissions : flags
• margin : real
• parent : Item
• target : Item
• translation : QVector2D
• xAxis
  • xAxis.enabled : bool
  • xAxis.maximum : real
  • xAxis.minimum : real
• yAxis
  • yAxis.enabled : bool
  • yAxis.maximum : real
  • yAxis.minimum : real

信号

• canceled (EventPoint point )
• grabChanged (GrabTransition transition , EventPoint point )

详细描述

DragHandler is a handler that is used to interactively move an Item. Like other Input Handlers, by default it is fully functional, and manipulates its target .

import QtQuick 2.12
Rectangle {
    width: 100
    height: 100
    color: "lightsteelblue"
    DragHandler { }
}
					

It has properties to restrict the range of dragging.

If it is declared within one Item but is assigned a different target , then it handles events within the bounds of the parent Item but manipulates the target Item instead:

import QtQuick 2.12
Item {
    width: 640
    height: 480
    Rectangle {
        id: feedback
        border.color: "red"
        width: Math.max(10, handler.centroid.ellipseDiameters.width)
        height: Math.max(10, handler.centroid.ellipseDiameters.height)
        radius: Math.max(width, height) / 2
        visible: handler.active
    }
    DragHandler {
        id: handler
        target: feedback
    }
}
					

A third way to use it is to set target to null and react to property changes in some other way:

import QtQuick 2.12
Item {
    width: 640
    height: 480
    DragHandler {
        id: handler
        target: null
    }
    Text {
        color: handler.active ? "darkgreen" : "black"
        text: handler.centroid.position.x.toFixed(1) + "," + handler.centroid.position.y.toFixed(1)
        x: handler.centroid.position.x - width / 2
        y: handler.centroid.position.y - height
    }
}
					

If minimumPointCount and maximumPointCount are set to values larger than 1, the user will need to drag that many fingers in the same direction to start dragging. A multi-finger drag gesture can be detected independently of both a (default) single-finger DragHandler and a PinchHandler on the same Item, and thus can be used to adjust some other feature independently of the usual pinch behavior: for example adjust a tilt transformation, or adjust some other numeric value, if the target is set to null. But if the target is an Item, centroid is the point at which the drag begins and to which the target will be moved (subject to constraints).

At this time, drag-and-drop is not yet supported.

另请参阅 Drag and MouseArea .

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).

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.

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。