如何解决React-konva 移动缩放和可拖动图像
我正在使用 Konva.js 构建一个画布应用程序。此应用程序允许用户拖动图像并在任何点进行缩放。这在桌面上完美运行。但是,我喜欢这个应用程序能够响应移动设备。这里的问题是画布缩放和图像拖动不能同步工作。由于“onTouchMove”事件在图像拖动时起作用,因此此应用无法按预期运行。
import React,{ useEffect,useState,useRef } from 'react';
import {
Stage,Layer,Image,} from 'react-konva';
import Rectangle from './rectangle.component';
const GenericCanvas = ({
canvasWidth,canvasHeight,imageUrl,imgWidth,imgHeight,rects,zoom,imageMove,alpha,borderDash,rectDraggable,fillStatus,onClickRect,reset,setReset,imageType,displayedfigure,displayedTable,clickedRect
}) => {
const [image,setimage] = useState(null);
const [stageScale,setStageScale] = useState(1);
const [stageX,setStageX] = useState(0);
const [stageY,setStageY] = useState(0);
const [lastX,setLastX] = useState(0);
const [lastY,setLastY] = useState(0);
const [hasImageLoaded,setHasImageLoaded] = useState(false);
const handleImageLastPosition = (e) => {
setLastX(e.target.attrs.x);
setLastY(e.target.attrs.y);
};
const handleWheel = (e) => {
e.evt.preventDefault();
const scaleBy = 1.2;
const stage = e.target.getStage();
const oldScale = stage.scaleX();
const mousePointTo = {
x: stage.getPointerPosition().x / oldScale - stage.x() / oldScale,y: stage.getPointerPosition().y / oldScale - stage.y() / oldScale,};
const newScale = e.evt.deltaY > 0
? (oldScale > 3 ? oldScale : (oldScale * scaleBy)) : oldScale < 1
? oldScale : (oldScale / scaleBy);
setStageScale(newScale);
setStageX(-(mousePointTo.x - stage.getPointerPosition().x / newScale) * newScale);
setStageY(-(mousePointTo.y - stage.getPointerPosition().y / newScale) * newScale);
};
function getdistance(p1,p2) {
return Math.sqrt(Math.pow(p2.x - p1.x,2) + Math.pow(p2.y - p1.y,2));
}
function getCenter(p1,p2) {
return {
x: (p1.x + p2.x) / 2,y: (p1.y + p2.y) / 2,};
}
var lastCenter = null;
var lastdist = 0;
const handleMultiTouch = (e) => {
e.evt.preventDefault();
var touch1 = e.evt.touches[0];
var touch2 = e.evt.touches[1];
const stage = e.target.getStage();
if (touch1 && touch2) {
if (stage.isDragging()) {
stage.stopDrag();
}
imageMove= false;
var p1 = {
x: touch1.clientX,y: touch1.clientY,};
var p2 = {
x: touch2.clientX,y: touch2.clientY,};
if (!lastCenter) {
lastCenter = getCenter(p1,p2);
return;
}
var newCenter = getCenter(p1,p2);
var dist = getdistance(p1,p2);
if (!lastdist) {
lastdist = dist;
}
// local coordinates of center point
var pointTo = {
x: (newCenter.x - stage.x()) / stage.scaleX(),y: (newCenter.y - stage.y()) / stage.scaleX(),};
var scale = stage.scaleX() * (dist / lastdist);
stage.scaleX(scale);
stage.scaleY(scale);
// calculate new position of the stage
var dx = newCenter.x - lastCenter.x;
var dy = newCenter.y - lastCenter.y;
var newPos = {
x: newCenter.x - pointTo.x * scale + dx,y: newCenter.y - pointTo.y * scale + dy,};
stage.position(newPos);
stage.batchDraw();
lastdist = dist;
lastCenter = newCenter;
}
};
const multiTouchEnd = () => {
lastCenter = null;
lastdist = 0;
}
useEffect(() => {
setHasImageLoaded(false);
if (imageUrl) {
const matchedImg = new window.Image();
matchedImg.src = `${API_URL + imageUrl}`;
matchedImg.onload = () => {
setHasImageLoaded(true);
setimage(matchedImg);
};
}
},[size,imageUrl]);
let imgDraggable = true
return (
<Stage
width={canvasWidth}
height={canvasHeight}
onWheel={zoom ? handleWheel : null}
scaleX={stageScale}
onTouchMove={handleMultiTouch}
onTouchEnd={() => {
multiTouchEnd()
}}
scaleY={stageScale}
x={stageX}
y={stageY}
>
<Layer>
<Image
x={lastX}
y={lastY}
ref={stageRef}
image={image}
width={imgWidth * alpha || 0}
height={imgHeight * alpha || 0}
onDragMove={(e) => {
if (e.evt.touches.length === 2) {
imgDraggable = false
}
handleImageLastPosition(e)
}}
draggable={imgDraggable}
/>
{rects?.length && hasImageLoaded ?
rects.map((rect) =>
(
<Rectangle
key={uuid()}
x={imageType === 'figure' ? rect.bBox.x0 * alpha + lastX : rect.PN_bBox.x0 * alpha + lastX}
y={imageType === 'figure' ? rect.bBox.y0 * alpha + lastY : rect.PN_bBox.y0 * alpha + lastY}
width={imageType === 'figure' ? rect.bBox.x1 * alpha - rect.bBox.x0 * alpha : rect.PN_bBox.x1 * alpha - rect.PN_bBox.x0 * alpha}
height={imageType === 'figure' ? rect.bBox.y1 * alpha - rect.bBox.y0 * alpha : rect.PN_bBox.y1 * alpha - rect.PN_bBox.y0 * alpha}
rectDraggable={rectDraggable}
borderDash={borderDash}
lastX={lastX}
lastY={lastY}
alpha={alpha}
rect={rect}
fillStatus={clickedRect?.item_no === rect?.item_no}
imageId={imageType === 'table' ? displayedTable?.img_id : displayedfigure?.img_id}
imageType={imageType}
onClickRect={onClickRect}
/>
)
) : null
}
</Layer>
</Stage>
);
};
我尝试控制触摸事件长度,因为如果它是 2,这意味着它来自多点触控,因此可以激活缩放,反之亦然。然而,它也没有奏效。提前感谢您的任何帮助。该演示可以在 https://codesandbox.io/s/react-konva-zoom-webmobile-demo-em5o6 上找到。
解决方法
您的沙箱代码中的问题似乎与此部分有关:
if (stage.isDragging()) {
stage.stopDrag();
}
首先,它检查是否正在拖动 STAGE,而不是图像。但即使我们将舞台设置为可拖动并开始拖动它,此检查无论如何都会返回 FALSE,因为我认为它完成得太早了。
一种解决方案是添加一个新的状态标志,例如 isZooming 并在注册多点触控时将其设置为 TRUE。然后我们可以将 onDragStart
添加到图像道具中,如果 isZooming 为 TRUE,我们在句柄函数中运行 stage.stopDrag()
。
这是您的沙箱示例的修改版本:
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