93 lines
2.9 KiB
React
93 lines
2.9 KiB
React
import React, { useRef, useState, useEffect } from 'react';
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import './SignaturePad.css';
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export default function SignaturePad() {
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const pad = useRef(null);
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const canvas = useRef(null);
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const drawing = useRef(false);
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const last = useRef(null);
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const strokes = useRef([]);
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const cur = useRef([]);
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const [hasInk, setHasInk] = useState(false);
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const [saved, setSaved] = useState('');
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const ctx = () => canvas.current.getContext('2d');
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const fit = () => {
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const r = pad.current.getBoundingClientRect();
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canvas.current.width = r.width;
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canvas.current.height = r.height;
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redraw();
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};
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const pos = (e) => {
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const r = canvas.current.getBoundingClientRect();
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const t = e.touches && e.touches[0];
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return { x: (t ? t.clientX : e.clientX) - r.left, y: (t ? t.clientY : e.clientY) - r.top };
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};
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const down = (e) => {
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e.preventDefault();
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drawing.current = true;
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last.current = pos(e);
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cur.current = [last.current];
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strokes.current.push(cur.current);
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setHasInk(true);
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};
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const move = (e) => {
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if (!drawing.current) return;
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e.preventDefault();
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const p = pos(e);
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ctx().lineTo(p.x, p.y);
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ctx().stroke();
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cur.current.push(p);
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};
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const up = () => { drawing.current = false; last.current = null; };
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const undo = () => { strokes.current.pop(); redraw(); if (!strokes.current.length) setHasInk(false); };
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const clear = () => { strokes.current = []; redraw(); setHasInk(false); setSaved(''); };
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const save = () => setSaved('已导出（' + canvas.current.width + '×' + canvas.current.height + '）');
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const redraw = () => {
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const c = canvas.current;
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const x = c.getContext('2d');
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x.clearRect(0, 0, c.width, c.height);
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x.strokeStyle = '#1F2329';
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x.lineWidth = 2;
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x.lineCap = 'round';
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x.lineJoin = 'round';
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strokes.current.forEach((s) => {
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x.beginPath();
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s.forEach((p, i) => (i ? x.lineTo(p.x, p.y) : x.moveTo(p.x, p.y)));
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x.stroke();
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});
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};
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useEffect(() => {
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fit();
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window.addEventListener('resize', fit);
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return () => window.removeEventListener('resize', fit);
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// eslint-disable-next-line
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}, []);
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return (
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<div className="aa-sign">
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<div className="aa-sign-pad" ref={pad}>
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<canvas
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ref={canvas}
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className="aa-sign-canvas"
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onMouseDown={down}
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onMouseMove={move}
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onMouseUp={up}
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onTouchStart={down}
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onTouchMove={move}
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onTouchEnd={up}
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/>
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{!hasInk && <div className="aa-sign-placeholder">请在此处签名</div>}
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</div>
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<div className="aa-sign-actions">
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<button className="aa-btn" onClick={undo}>撤销</button>
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<button className="aa-btn" onClick={clear}>清除</button>
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<button className="aa-btn aa-btn--primary" onClick={save}>保存</button>
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{saved && <span className="aa-sign-preview">{saved}</span>}
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</div>
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</div>
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);
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}
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