HTML realizes dragging content position at will

Two ways are: dragging the normal label position or dragging the text box position in the canvas

1. Implement mouse dragging of labels Element to any position

css code

#range { position: relative; width: 600px; height: 400px; margin: 10px; background-color: rgb(133, 246, 250); } .icon { position: absolute; height: 100px; width: 100px; cursor: move; background-color: #ff9204; user-select: none; }

html code

 
100*100
 

js code

const main = document.getElementById('range'); const icon = document.querySelector('.icon'); let move = false; let deltaLeft = 0, deltaTop = 0; // 拖动开始事件，要绑定在被移动元素上 icon.addEventListener('mousedown', function (e) { /* * @des deltaLeft 即移动过程中不变的值 */ deltaLeft = e.clientX-e.target.offsetLeft; deltaTop = e.clientY-e.target.offsetTop; move = true; }) // 移动触发事件要放在，区域控制元素上 main.addEventListener('mousemove', function (e) { if (move) { const cx = e.clientX; const cy = e.clientY; /** 相减即可得到相对于父元素移动的位置 */ let dx = cx - deltaLeft let dy = cy - deltaTop /** 防止超出父元素范围 */ if (dx < 0) dx = 0 if (dy < 0) dy = 0 if (dx > 500) dx = 500 if (dy > 300) dy = 300 icon.setAttribute('style', `left:${dx}px;top:${dy}px`) } }) // 拖动结束触发要放在，区域控制元素上 main.addEventListener('mouseup', function (e) { move = false; console.log('mouseup'); })

2 .Canvas draws a text box and drags it to any position with the mouse

css code

.cus-canvas{ background: rgb(50, 204, 243); } .input-ele{ display: none; position: fixed; width: 180px; border: 0; background-color: #fff; }

html code

js code

The implementation principle is to record the position of the mouse movement and continuously redraw the rectangular frame and text content

let mouseDown = false; let deltaX = 0; let deltaY = 0; let text = 'hello' const canvas = document.getElementById('canvas'); const ctx = canvas.getContext('2d'); const cw = canvas.width, ch = canvas.height; const rect = { x: 20, y: 20, width: 150, height: 50 } /** 设置文字和边框样式 */ ctx.font="16px Arial"; ctx.fillStyle = "#fff"; /** 设置为 center 时，文字段的中心会在 fillText的 x 点 */ ctx.textAlign = 'center'; ctx.lineWidth = '2'; ctx.strokeStyle = '#fff'; strokeRect() const inputEle = document.getElementById('inputEle'); inputEle.onkeyup = function(e) { if(e.keyCode === 13) { text = inputEle.value strokeRect() inputEle.setAttribute('style', `display:none`) } } canvas.ondblclick = function(e){ inputEle.setAttribute('style', `left:${e.clientX}px;top:${e.clientY}px;display:block`); inputEle.focus(); } canvas.onmousedown = function(e){ /** 获取视口左边界与canvas左边界的距离 加上 鼠标点击位置与canvas左边界的长度，这个值是相对移动过程中不变的值 */ deltaX=e.clientX - rect.x; deltaY=e.clientY - rect.y; mouseDown = true }; const judgeW = cw-rect.width, judgeH = ch-rect.height; canvas.onmousemove = function(e){ if(mouseDown) { /** 相减即可获得矩形左边界与canvas左边界之间的长度 */ let dx = e.clientX-deltaX; let dy = e.clientY-deltaY; if(dx < 0) { dx = 0; } else if (dx > judgeW) { dx = judgeW; } if(dy < 0) { dy = 0; } else if(dy > judgeH) { dy = judgeH; } rect.x = dx; rect.y = dy; strokeRect() } }; canvas.onmouseup = function(e){ mouseDown = false }; /** 清除指定区域 */ function clearRect() { ctx.clearRect(0, 0, cw, ch) } /** 画矩形 */ function strokeRect() { clearRect() /** 这里如果不调用 beginPath 历史的矩形会重新被绘制 */ ctx.beginPath() ctx.rect(rect.x, rect.y, rect.width, rect.height) ctx.stroke(); // 设置字体内容，以及在画布上的位置 ctx.fillText(text, rect.x + 70, rect.y + 30); }

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