Qt QML Shape：如何强制以干净的方式更新数据属性？

我正在尝试创建一个窗口，在那里我可以绘制三角形，并用形状{}删除其中任何一个。在下面的示例中，我可以绘制两种类型的三角形：

• 上三角：绿色和填充
• 向下三角形：黄色且未填充

基本上，我选择三角形的类型（在右下角有一个按钮），然后单击窗口上的任意位置以获得三角形

单击后，将动态创建三角形，并将其存储在属性triangleList中。然后调用函数shape.update（）来更新shape的数据属性。这部分很好用

这里是我在形状中使用的函数update（因为数据是一个列表，所以我必须重新分配给一个新列表）：

函数更新（）
{
数据=[]；
var d=[]；
对于（变量i=0；i

当我尝试删除三角形时，问题出现了。在我的示例中，我可以删除第一个、最后一个或所有三角形。删除三角形时，首先删除triangleList中的值，然后再次调用shape.update（）。当我删除所有三角形或最后一个三角形时，它会起作用

但是，当我尝试删除第一个三角形时，数据不会更新其对象，即使我给它一个新列表。事实上，它总是删除最后一个三角形。下面是一个例子：

数据属性知道少了一个三角形，但不会更新其他三角形。我找到的唯一解决方案是更改属性，然后返回原始值。这样，它会强制更新数据。 但是我必须为每个不同的属性（颜色和位置）这样做。因此，我的update（）函数如下所示：

for (var i = 0; i < canvas.triangleList.length; i++)
                {
    d.push( canvas.triangleList[i] );

    ////// Change properties one by one to force the refresh

    // Force path redraw. Otherwise only the last path can be deleted
    d[i].startX++;d[i].startX--;

    // Force line color update
    d[i].strokeColor = "red"
    d[i].strokeColor = d[i].isUp ? "green" : "yellow";

    // Force fill color update
    d[i].fillColor = "red";
    d[i].fillColor = d[i].isUp ? "green" : "transparent";

    data = d;
}

for（变量i=0；i

我邀请您对这些行进行注释，以了解差异。 我可以使用这个技巧来强制更新，但是我的实际代码比这个示例要大，我使用绑定

所以我的问题是：有没有一种方法可以强制更新而不必更改每个属性？

如果要测试它，请参阅完整代码：

import QtQuick 2.9;
import QtQuick.Controls 2.2;
import QtQuick.Shapes 1.0;

ApplicationWindow {
    visible: true; width: 640; height: 480;

    Rectangle {
        id: canvas;
        anchors.fill: parent;
        color: "black";
        property var triangleList: [];
        property bool triangleUp: true;

        MouseArea {
            anchors.fill: parent;
            onClicked: {
                var triangle = componentTriangle.createObject(componentTriangle, {
                                                                "isUp" :  canvas.triangleUp,
                                                                "startX" :  mouse.x,
                                                                "startY" :  mouse.y,
                                                               }, canvas);

                canvas.triangleList.push(triangle);
                shape.update();
            }
        }   // MouseArea

        Shape {
            id: shape;

            anchors.fill: parent;

            function update()
            {
                data = [];
                var d = [];

                for (var i = 0; i < canvas.triangleList.length; i++)
                {
                    d.push( canvas.triangleList[i] );

                    ///////////// HOW TO AVOID THE PART BELOW? /////////////
                    ////// Change properties one by one to force the refresh

                    // Force path redraw. Otherwise only the last path can be deleted
                    d[i].startX++;d[i].startX--;

                    // Force line color update
                    d[i].strokeColor = "red"
                    d[i].strokeColor = d[i].isUp ? "green" : "yellow";

                    // Force fill color update
                    d[i].fillColor = "red";
                    d[i].fillColor = d[i].isUp ? "green" : "transparent";

                    //////////////////////////////////////////////////////
                }

                data = d;

                // I make sure data has at least one path to ensure the refresh
                if (data.length == 0)
                    data.push(Qt.createQmlObject('import QtQuick 2.9; import QtQuick.Shapes 1.0; ShapePath {startX:0;startY:0;}', canvas,
                              "force_refresh"));
            }
        }  // Shape
    }   // Rectangle

    //////////// Buttons to handle the triangles

    Column {
        anchors.bottom: parent.bottom;
        anchors.right: parent.right;

        Button {

            text: canvas.triangleUp? "Draw triangleUp" : "Draw triangleDown";
            onClicked: { canvas.triangleUp = !canvas.triangleUp; }
        }   // Button

        Button {
            text: "Clear first";
            onClicked: {
                canvas.triangleList[0].destroy();
                canvas.triangleList.splice(0,1);
                shape.update();
            }
        }   // Button

        Button {
            text: "Clear last";
            onClicked: {
                canvas.triangleList[canvas.triangleList.length -1].destroy();
                canvas.triangleList.splice(canvas.triangleList.length -1,1);
                shape.update();
            }
        }   // Button

        Button {
            text: "Clear all";
            onClicked: {
                for (var i = 0; i < canvas.triangleList.length; i++)
                    canvas.triangleList[i].destroy();
                canvas.triangleList = [];
                shape.update();
            }
        }   // Button
    }

    //////////// Component to draw the triangle
    Component {
        id: componentTriangle;

        ShapePath {
            property bool isUp;
            property real offsetX: isUp? -20 : 20;
            property real offsetY: isUp? -30 : 30;

            strokeColor: isUp ? "green" : "yellow";
            strokeWidth: 3;
            fillColor: isUp ? "green" : "transparent";

            PathLine { x: startX - offsetX; y: startY - offsetY }
            PathLine { x: startX + offsetX; y: startY - offsetY }
            PathLine { x: startX; y: startY }
        }   // ShapePath
    }
}

导入QtQuick 2.9；
导入QtQuick.Controls 2.2；
导入QtQuick.Shapes 1.0；
应用程序窗口{
可见：真；宽度：640；高度：480；
长方形{
id：画布；
锚固件。填充：父级；
颜色：“黑色”；
属性变量三角形列表：[]；
属性bool triangleUp：true；
鼠耳{
锚固件。填充：父级；
再次点击：{
var triangle=componentTriangle.createObject（componentTriangle{
“isUp”：canvas.triangleUp，
“startX”：mouse.x，
“startY”：mouse.y，
}，帆布）；
canvas.triangleList.push（三角形）；
shape.update（）；
}
}//鼠耳
形状{
id：形状；
锚固件。填充：父级；
函数更新（）
{
数据=[]；
var d=[]；
对于（变量i=0；iimport QtQuick 2.9;
import QtQuick.Controls 2.2;
import QtQuick.Shapes 1.0;

ApplicationWindow {
    visible: true; width: 640; height: 480;

    Rectangle {
        id: canvas;
        anchors.fill: parent;
        color: "black";
        property var triangleList: [];
        property bool triangleUp: true;

        MouseArea {
            anchors.fill: parent;
            onClicked: {
                var triangle = componentTriangle.createObject(componentTriangle, {
                                                                "isUp" :  canvas.triangleUp,
                                                                "startX" :  mouse.x,
                                                                "startY" :  mouse.y,
                                                               }, canvas);

                canvas.triangleList.push(triangle);
                shape.update();
            }
        }   // MouseArea

        Shape {
            id: shape;

            anchors.fill: parent;

            function update()
            {
                data = [];
                var d = [];

                for (var i = 0; i < canvas.triangleList.length; i++)
                {
                    d.push( canvas.triangleList[i] );

                    ///////////// HOW TO AVOID THE PART BELOW? /////////////
                    ////// Change properties one by one to force the refresh

                    // Force path redraw. Otherwise only the last path can be deleted
                    d[i].startX++;d[i].startX--;

                    // Force line color update
                    d[i].strokeColor = "red"
                    d[i].strokeColor = d[i].isUp ? "green" : "yellow";

                    // Force fill color update
                    d[i].fillColor = "red";
                    d[i].fillColor = d[i].isUp ? "green" : "transparent";

                    //////////////////////////////////////////////////////
                }

                data = d;

                // I make sure data has at least one path to ensure the refresh
                if (data.length == 0)
                    data.push(Qt.createQmlObject('import QtQuick 2.9; import QtQuick.Shapes 1.0; ShapePath {startX:0;startY:0;}', canvas,
                              "force_refresh"));
            }
        }  // Shape
    }   // Rectangle

    //////////// Buttons to handle the triangles

    Column {
        anchors.bottom: parent.bottom;
        anchors.right: parent.right;

        Button {

            text: canvas.triangleUp? "Draw triangleUp" : "Draw triangleDown";
            onClicked: { canvas.triangleUp = !canvas.triangleUp; }
        }   // Button

        Button {
            text: "Clear first";
            onClicked: {
                canvas.triangleList[0].destroy();
                canvas.triangleList.splice(0,1);
                shape.update();
            }
        }   // Button

        Button {
            text: "Clear last";
            onClicked: {
                canvas.triangleList[canvas.triangleList.length -1].destroy();
                canvas.triangleList.splice(canvas.triangleList.length -1,1);
                shape.update();
            }
        }   // Button

        Button {
            text: "Clear all";
            onClicked: {
                for (var i = 0; i < canvas.triangleList.length; i++)
                    canvas.triangleList[i].destroy();
                canvas.triangleList = [];
                shape.update();
            }
        }   // Button
    }

    //////////// Component to draw the triangle
    Component {
        id: componentTriangle;

        ShapePath {
            property bool isUp;
            property real offsetX: isUp? -20 : 20;
            property real offsetY: isUp? -30 : 30;

            strokeColor: isUp ? "green" : "yellow";
            strokeWidth: 3;
            fillColor: isUp ? "green" : "transparent";

            PathLine { x: startX - offsetX; y: startY - offsetY }
            PathLine { x: startX + offsetX; y: startY - offsetY }
            PathLine { x: startX; y: startY }
        }   // ShapePath
    }
}

import QtQuick 2.9;
import QtQuick.Controls 2.2;
import QtQuick.Shapes 1.0;

ApplicationWindow {
    visible: true; width: 640; height: 480;
    QtObject{
        id: internals
        property bool triangleUp: true;
    }
    ListModel{
        id: datamodel
    }
    Rectangle {
        id: canvas;
        anchors.fill: parent;
        color: "black";
        Repeater{
            model: datamodel
            Triangle{
                x: model.x
                y: model.y
                isUp: model.isUp
            }
        }
        MouseArea{
            anchors.fill: parent
            onClicked: datamodel.append({"x": mouse.x, "y": mouse.y, "isUp": internals.triangleUp})
        }
    }
    Column {
        anchors.bottom: parent.bottom;
        anchors.right: parent.right;
        Button {
            text: internals.triangleUp ? "Draw triangleUp" : "Draw triangleDown";
            onClicked: internals.triangleUp = !internals.triangleUp;
        }   // Button

        Button {
            text: "Clear first";
            onClicked: if(datamodel.count > 0) datamodel.remove(0)
        }   // Button

        Button {
            text: "Clear last";
            onClicked: if(datamodel.count > 0) datamodel.remove(datamodel.count - 1)
        }   // Button

        Button {
            text: "Clear all";
            onClicked: datamodel.clear()
        }   // Button
    }
}

import QtQuick 2.9;
import QtQuick.Shapes 1.0

Shape {
    id: shape
    property bool isUp: false
    QtObject{
        id: internals
        property real offsetX: isUp? -20 : 20;
        property real offsetY: isUp? -30 : 30;
    }
    ShapePath {
        strokeWidth: 3;
        strokeColor: isUp ? "green" : "yellow";
        fillColor: isUp ? "green" : "transparent";
        PathLine { x: -internals.offsetX ; y: -internals.offsetY }
        PathLine { x: internals.offsetX; y: -internals.offsetY }
        PathLine { x: 0; y: 0 }
    }
}