QML:如何拒绝丢弃动作 [英] QML: How to reject drop action

问题描述

我有一个 DropArea 和两个元素.如果 DropArea 已经有一个元素被丢弃，我希望 DropArea 拒绝丢弃事件，另一个元素不允许放入，除非第一个元素移出.

I have one DropArea and two elements. I want DropArea reject the drop event if the DropArea already got one element be dropped, the another element not allow drop into, unless the first one move out.

DropArea {
    property bool dropped: false

    onDropped: {
        drop.accepted = !dropped;
        dropped = true;
    }
    onExited: dropped = false
}

但看起来 drop.accepted 不起作用，顺便说一句，获取对象被丢弃在 DropArea

But looks like drop.accepted not work, BTW anyway to get the objects was dropped in DropArea

推荐答案

您应该在 onReleased 中控制是否必须删除项目，检查 dropped 属性.

You should control if the item must be dropped or not in onReleased, checking the dropped property.

完整示例:

import QtQuick 2.5
import QtQuick.Window 2.2
import QtQuick.Controls 1.4

Window {
    id: win
    visible: true
    width: 800
    height: 600
    title: qsTr("Hello World")

    Repeater {
        model: 10
        Rectangle {
            id: rect
            width: 50
            height: 50
            z: mouseArea.drag.active ||  mouseArea.pressed ? 2 : 1
            color: Qt.rgba(Math.random(), Math.random(), Math.random(), 1)
            x: Math.random() * (win.width / 2 - 100)
            y: Math.random() * (win.height - 100)
            property point beginDrag
            property bool caught: false
            border { width:2; color: "white" }
            radius: 5
            Drag.active: mouseArea.drag.active

            Text {
                anchors.centerIn: parent
                text: index
                color: "white"
            }
            MouseArea {
                id: mouseArea
                anchors.fill: parent
                drag.target: parent
                onPressed: {
                    rect.beginDrag = Qt.point(rect.x, rect.y);
                }
                onReleased: {
                    if(!rect.caught || dragTarget.dropped) {
                        backAnimX.from = rect.x;
                        backAnimX.to = beginDrag.x;
                        backAnimY.from = rect.y;
                        backAnimY.to = beginDrag.y;
                        backAnim.start()
                    }

                    parent.Drag.drop()

                    console.log("MouseArea - containsDrag " + dragTarget.dropped)
                }

            }
            ParallelAnimation {
                id: backAnim
                SpringAnimation { id: backAnimX; target: rect; property: "x";
                                  duration: 500; spring: 2; damping: 0.2 }
                SpringAnimation { id: backAnimY; target: rect; property: "y";
                                  duration: 500; spring: 2; damping: 0.2 }
            }
        }
    }

    Rectangle {
        anchors {
            top: parent.top
            right:  parent.right
            bottom:  parent.bottom
        }
        width: parent.width / 2
        color: "gold"
        DropArea {
            id: dragTarget
            anchors.fill: parent

            property bool dropped: false

            onEntered: {
                console.log("onEntered " + containsDrag)
                drag.source.caught = true;
            }
            onExited: {
                console.log("onExited " + containsDrag)
                dropped = false;
            }
            onDropped:
            {
                console.log("onDropped");
                dropped = true;
            }
        }
    }
}

这篇关于QML:如何拒绝丢弃动作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！