import QtQuick 2.4 import QtQuick.Controls 2.5 import QtQuick.Window 2.3 ApplicationWindow { visible: true width: 800 height: 600 title: "Drawing Board Example" Item { width: 700 height: 500 property int gridSize: 20 property int scaleFactor: 100 Canvas { id: canvas anchors.fill: parent onPaint: { var ctx = getContext("2d"); var width = canvas.width; var height = canvas.height; // 清除画布 ctx.clearRect(0, 0, width, height); ctx.lineWidth = 0.002 * parent.scaleFactor; // 绘制网格线 ctx.strokeStyle = "black"; for (var x = 0; x <= width; x += parent.gridSize) { ctx.beginPath(); ctx.moveTo(x, 0); ctx.lineTo(x, height); ctx.stroke(); } for (var y = 0; y <= height; y += parent.gridSize) { ctx.beginPath(); ctx.moveTo(0, y); ctx.lineTo(width, y); ctx.stroke(); } } } MouseArea { anchors.fill: parent property int gridSize: parent.gridSize property int scaleFactor: parent.scaleFactor onWheel: { // 根据滚轮事件的delta属性,计算缩放比例 parent.scaleFactor += wheel.angleDelta.y / 120; parent.scaleFactor = Math.max(parent.scaleFactor, 10); // 最小值为10% // 根据缩放比例重新计算gridSize和canvas的宽度和高度 parent.gridSize = parent.scaleFactor / 5; canvas.width = width * parent.scaleFactor / 100; canvas.height = height * parent.scaleFactor / 100; canvas.requestPaint(); } } } }我需要在这段代码的基础上增加一个button按钮,他的功能是点击后,鼠标具有一个长按绘制矩形的功能,在按下的期间保留该矩形的绘制过程
时间: 2024-03-17 14:41:49 浏览: 105
Qt Quick App的两种启动方式.docx
您可以按照以下的步骤来增加一个button按钮,并实现长按绘制矩形的功能:
1. 在Item内部增加一个Button组件,如下:
```
Button {
id: rectButton
text: "Draw Rectangle"
anchors.bottom: parent.bottom
anchors.horizontalCenter: parent.horizontalCenter
}
```
2. 增加一个矩形绘制的函数`drawRect`,如下:
```
function drawRect(x, y, width, height) {
var ctx = canvas.getContext("2d");
ctx.strokeStyle = "red";
ctx.strokeRect(x, y, width, height);
}
```
3. 在MouseArea内部增加长按事件的处理,如下:
```
MouseArea {
// ...
property var rectStartPos: null
property var rectEndPos: null
onLongPressed: {
rectStartPos = mapToItem(canvas, mouse.x, mouse.y);
}
onLongPressCanceled: {
rectStartPos = null;
rectEndPos = null;
}
onPositionChanged: {
if (rectStartPos !== null) {
rectEndPos = mapToItem(canvas, mouse.x, mouse.y);
canvas.requestPaint();
}
}
}
```
4. 在Canvas的onPaint回调函数中增加绘制矩形的代码,如下:
```
Canvas {
// ...
onPaint: {
// ...
if (mouseArea.rectStartPos !== null && mouseArea.rectEndPos !== null) {
var x = Math.min(mouseArea.rectStartPos.x, mouseArea.rectEndPos.x);
var y = Math.min(mouseArea.rectStartPos.y, mouseArea.rectEndPos.y);
var width = Math.abs(mouseArea.rectStartPos.x - mouseArea.rectEndPos.x);
var height = Math.abs(mouseArea.rectStartPos.y - mouseArea.rectEndPos.y);
drawRect(x, y, width, height);
}
}
}
```
这样,当用户长按button按钮后,鼠标移动时,画布上会实时绘制一个矩形。当用户松开鼠标时,矩形绘制结束。
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