新手村21 - Speech Detection

21 - Geolocation

俗話說的好，一天一蘋果，醫生遠離我

一天一 JS，What the f*ck JavaScript？

small steps every day - 記錄著新手村日記

完成目標

地理資訊的功能

  • 功能
    • 抓到指北角度要改畫面
    • 抓到移動速度要更新畫面
  • 畫面
    • 指北轉要旋轉
    • 顯示移動速度

index_START.html

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <meta name="viewport" content="width=device-width">
</head>
<body>
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  <h1 class="speed">
    <span class="speed-value">0</span>
    <span class="units">KM/H</span>
  </h1>

  <style>
    html {
      font-size: 100px;
    }
    
    body {
      margin: 0;
      font-family: sans-serif;
      min-height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
      flex-direction: column;
      background:
        radial-gradient(black 15%, transparent 16%) 0 0,
        radial-gradient(black 15%, transparent 16%) 8px 8px,
        radial-gradient(rgba(255,255,255,.1) 15%, transparent 20%) 0 1px,
        radial-gradient(rgba(255,255,255,.1) 15%, transparent 20%) 8px 9px;
      background-color: #282828;
      background-size: 16px 16px;
      background-attachment: fixed;
    }

    .arrow {
      width: 250px;
      overflow: hidden;
      transition: all 0.2s;
      transform: rotate(0deg);
      display: inline-block;
    }

    h1 {
      color: white;
      font-weight: 100;
      font-size: 60px;
      display: flex;
      align-items: center;
    }

    .units {
      font-size: 15px;
    }
    /*Compass: https://thenounproject.com/search/?q=compass&i=592352*/
  </style>
  <script>
  </script>
</body>
</html>

JS - step by step

首先，先將 Class arrow 、speed 透過 querySelector 抓出來命名為變數 arrow、speed 方便我們之後使用

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<script>
    const arrow = document.querySelector('.arrow');
    const speed = document.querySelector('.speed-value');
</script>

透過 Geolocation.watchPosition() 來註冊一個處理的函式，當使用者的裝置位置更新時，這個函式所傳入的回呼函式(callback function) 就會自動被呼叫，也可以選擇性的定義錯誤時哪些錯誤回呼函式需要被呼叫

Geolocation.watchPosition()：https://tinyurl.com/y5b9m2kw

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<script>
    const arrow = document.querySelector('.arrow');
    const speed = document.querySelector('.speed-value');

    navigator.geolocation.watchPosition((data) => {
      console.log(data);
    });
		// Position {coords: Coordinates, timestamp: 1570368253203}
</script>

在這段內容中應該如何取得速度及方位呢？ 可以透過 coords.speed 這個方法來取得速度，並用 coords.heading 取得方位，再透過 CSS 將 Class arrow 旋轉角度即可表示現在的方位。此外，如果回傳錯誤的話就在 console 中顯示 err 的內容！

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<script>
    const arrow = document.querySelector('.arrow');
    const speed = document.querySelector('.speed-value');

    navigator.geolocation.watchPosition((data) => {
      console.log(data);
      speed.textContent = data.coords.speed;
      arrow.style.transform = `rotate(${data.coords.heading}deg)`;
    }), (err) => {
      console.error(err);
    });
</script>

就大功告成啦！（覺得這個經緯度真的準的有點誇張w

JS - final

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<script>
    const arrow = document.querySelector('.arrow');
    const speed = document.querySelector('.speed-value');

    navigator.geolocation.watchPosition((data) => {
      console.log(data);
      speed.textContent = data.coords.speed;
      arrow.style.transform = `rotate(${data.coords.heading}deg)`;
    }, (err) => {
      console.error(err);
    });
</script>

本刊同步於個人網站：http://chestertang.site/

本次範例程式碼原作者來源：https://tinyurl.com/yavm5f5n