如何制作一个交互式按钮，单击时在其周围创建一个半圆

Question

所以我想在屏幕底部创建一个 go 的按钮，并在单击时在其周围创建一个带有更多按钮的半圆。 我试过调整 CSS 但我无法提出解决方案。 你们知道有什么方法吗？ 我遇到了这个codepen（“https://codepen.io/jet/pen/LwiGu”），这几乎正是我想要的，而不是围绕它创建一个完整的圆圈，它会在顶部创建一个半圆。 我附上一张图片让你们更好地理解它。

 var items = document.querySelectorAll('.menuItem'); for(var i = 0, l = items.length; i < l; i++) { items[i].style.left = (50 - 35*Math.cos(-0.5 * Math.PI - 2*(1/l)*i*Math.PI)).toFixed(4) + "%"; items[i].style.top = (50 + 35*Math.sin(-0.5 * Math.PI - 2*(1/l)*i*Math.PI)).toFixed(4) + "%"; } document.querySelector('.center').onclick = function(e) { e.preventDefault(); document.querySelector('.circle').classList.toggle('open'); }

 @import "https://netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.css"; body { /* Image source: http://wallbase.cc/wallpaper/718405 */ /* Excuse the base64 mess, imgur blocked the hotlinked image and this seemed like the fastest solution */ background: cornflowerblue url(" 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Zpi/fmqdy2rnzMz353xFjTgzu5p0PB3MzUvfejadZ10VRoZ/25gWtI0d+7VvgXlX4MlL+z7+U9/w/sgwZKH+EVWgAAAABJRU5ErkJggg==") no-repeat fixed; background-size: cover; } a { font-size: 14px; text-decoration: none; outline: 0; }.circle, .ring { height: 256px; position: relative; width: 256px; }.circle { margin: 0 auto; }.ring { background-color: rgba(0,0,0,0.5); border-radius: 50%; opacity: 0; -webkit-transform-origin: 50% 50%; -moz-transform-origin: 50% 50%; transform-origin: 50% 50%; -webkit-transform: scale(0.1) rotate(-270deg); -moz-transform: scale(0.1) rotate(-270deg); -transform: scale(0.1) rotate(-270deg); -webkit-transition: all 0.4s ease-out; -moz-transition: all 0.4s ease-out; transition: all 0.4s ease-out; }.open.ring { opacity: 1; -webkit-transform: scale(1) rotate(0); -moz-transform: scale(1) rotate(0); transform: scale(1) rotate(0); }.center { background-color: rgba(255,255,255,0.3); border-radius: 50%; border: 2px solid #ffffff; bottom: 0; color: white; height: 80px; left: 0; line-height: 80px; margin: auto; position: absolute; right: 0; text-align: center; top: 0; width: 80px; -webkit-transition: all 0.4s ease-out; -moz-transition: all 0.4s ease-out; transition: all 0.4s ease-out; }.open.center { border-color: #aaaaaa; }.menuItem { border-radius: 50%; color: #eeeeee; display: block; height: 40px; line-height: 40px; margin-left: -20px; margin-top: -20px; position: absolute; text-align: center; width: 40px; }

 <div class="circle"> <div class="ring"> <a href="" class="menuItem fa fa-home fa-2x"></a> <a href="" class="menuItem fa fa-comment fa-2x"></a> <a href="" class="menuItem fa fa-play fa-2x"></a> <a href="" class="menuItem fa fa-camera fa-2x"></a> <a href="" class="menuItem fa fa-music fa-2x"></a> <a href="" class="menuItem fa fa-user fa-2x"></a> <a href="" class="menuItem fa fa-trash-o fa-2x"></a> <a href="" class="menuItem fa fa-star fa-2x"></a> </div> <a href="#" class="center fa fa-th fa-2x"></a> </div>

[菜单样机][1] [1]：https://i.stack.imgur.com/GR419.png

Answer 1

如果我正确理解你的愿望，那么你所要做的就是改变：

• .ring当前的高度和宽度为 256 像素，如果您希望它更大/更小，请更改它。
• 现在重新定位.ring使其与容器底部对齐。 您可以通过设置正好为.ring height一半的负bottom来做到这一点（例如bottom: -128px; ）。
• 现在您必须决定那里需要多少个图标（您的源中曾经有 8 个按钮，但现在我们剪掉了它，只有 4 个可见）。
• 现在，调整 2 个 javascript 行（其中包含...Math.PI...的行）以考虑
  • (A) 你想要的图标数量和
  • (B) 您只想填充.ring的上半部分

2 条Math.PI行（设置每个单独按钮的 position 并不复杂，但您必须如何更改它们完全取决于您制作的东西有多大，以及您想在上面放置多少个按钮 -所以我不能在不知道的情况下提供一个例子。