javascript - 为什么在这个 Vue 3 应用程序中无法将计算属性绑定(bind)为内联样式？

Question

我正在使用 Vue 3 和 Napster API 开发音频播放器。

项目详情

播放器有一个进度条。我使用 trackProgress 计算属性来实时更新进度:

<div class="progress-bar">
   <span :style="{ width: trackProgress + '%' }"></span>
 </div>

const musicApp = {
  data() {
    return {
      player: new Audio(),
      trackCount: 0,
      tracks: [],
      muted: false,
      isPlaying: false
    };
  },
  methods: {
    async getTracks() {
      try {
        const response = await axios
          .get(
            "https://api.napster.com/v2.1/tracks/top?apikey=ZTk2YjY4MjMtMDAzYy00MTg4LWE2MjYtZDIzNjJmMmM0YTdm"
          )
          .catch((error) => {
            console.log(error);
          });
        this.tracks = response;
        this.tracks = response.data.tracks;
      } catch (error) {
        console.log(error);
      }
    },
    nextTrack() {
      if (this.trackCount < this.tracks.length - 1) {
        this.trackCount++;
        this.setPlayerSource();
        this.playPause();
      }
    },
    prevTrack() {
      if (this.trackCount >= 1) {
        this.trackCount--;
        this.setPlayerSource();
        this.playPause();
      }
    },
    setPlayerSource() {
      this.player.src = this.tracks[this.trackCount].previewURL;
    },
    playPause() {
      if (this.player.paused) {
        this.isPlaying = true;
        this.player.play();
      } else {
        this.isPlaying = false;
        this.player.pause();
      }
    },
    toggleMute() {
      this.player.muted = !this.player.muted;
      this.muted = this.player.muted;
    }
  },
  async created() {
    await this.getTracks();
    this.setPlayerSource();
    this.player.addEventListener("ended", () => {
      this.isPlaying = false;
    });
  },
  computed: {
    trackProgress() {
      this.player.addEventListener("loadedmetadata", () => {
        return (this.player.currentTime / this.player.duration) * 100;
      });
    }
  }
};

Vue.createApp(musicApp).mount("#audioPlayer");

html,
body {
  margin: 0;
  padding: 0;
  font-size: 16px;
}

body * {
  box-sizing: border-box;
  font-family: "Montserrat", sans-serif;
}

@-webkit-keyframes spin {
  0% {
    -webkit-transform: rotate(0deg);
  }
  100% {
    -webkit-transform: rotate(360deg);
  }
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}

.player-container {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #2998ff;
  background-image: linear-gradient(62deg, #2998ff 0%, #5966eb 100%);
}

#audioPlayer {
  width: 300px;
  height: 300px;
  border-radius: 8px;
  position: relative;
  overflow: hidden;
  background-color: #00ca81;
  background-image: linear-gradient(160deg, #00ca81 0%, #ffffff 100%);
  box-shadow: 0 0.125rem 0.25rem rgba(0, 0, 0, 0.075);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.volume {
  color: #ff0057;
  opacity: 0.9;
  display: inline-block;
  width: 20px;
  font-size: 20px;
  position: absolute;
  top: 5px;
  right: 6px;
  cursor: pointer;
}

.album {
  width: 100%;
  flex: 1;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
}

.album-items {
  padding: 0 10px;
  text-align: center;
}

.cover {
  width: 150px;
  height: 150px;
  margin: auto;
  box-shadow: 0px 5px 12px 0px rgba(0, 0, 0, 0.17);
  border-radius: 50%;
  background: url("https://w7.pngwing.com/pngs/710/955/png-transparent-vinyl-record-artwork-phonograph-record-compact-disc-lp-record-disc-jockey-symbol-miscellaneous-classical-music-sound.png") center top transparent;
  background-size: cover;
}

.cover.spinning {
  webkit-animation: spin 6s linear infinite;
  /* Safari */
  animation: spin 6s linear infinite;
}

.info {
  width: 100%;
  padding-top: 5px;
  color: #000;
  opacity: 0.85;
}

.info h1 {
  font-size: 11px;
  margin: 5px 0 0 0;
}

.info h2 {
  font-size: 10px;
  margin: 3px 0 0 0;
}

.to-bottom {
  width: 100%;
  margin-top: auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
}

.progress-bar {
  background-color: #ff0057;
  opacity: 0.9;
  height: 3px;
  width: 100%;
}

.progress-bar span {
  display: block;
  height: 3px;
  width: 0;
  background: rgba(255, 255, 255, 0.4);
}

.controls {
  width: 150px;
  display: flex;
  height: 60px;
  justify-content: space-between;
  align-items: center;
}

.controls .navigate {
  display: flex;
  box-shadow: 1px 2px 7px 2px rgba(0, 0, 0, 0.09);
  width: 33px;
  height: 33px;
  line-height: 1;
  color: #ff0057;
  cursor: pointer;
  background: #fff;
  opacity: 0.9;
  border-radius: 50%;
  text-align: center;
  justify-content: center;
  align-items: center;
}

.controls .navigate.disabled {
  pointer-events: none;
  color: #606060;
  background-color: #f7f7f7;
}

.controls .navigate.navigate-play {
  width: 38px;
  height: 38px;
}

.navigate-play .fa-play {
  margin-left: 3px;
}

<link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet" />
<script src="https://unpkg.com/axios@0.22.0/dist/axios.min.js"></script>
<script src="https://unpkg.com/vue@next"></script>
<link href="https://fonts.googleapis.com/css2?family=Montserrat:wght@300;500&display=swap" rel="stylesheet">

<div class="player-container">
  <div id="audioPlayer">
    <span class="volume" @click="toggleMute">
      <i v-show="!muted" class="fa fa-volume-up"></i>
      <i v-show="muted" class="fa fa-volume-off"></i>
    </span>
    <div class="album">
      <div class="album-items">
        <div class="cover" :class="{'spinning' : isPlaying}"></div>
        <div class="info">
          <h1>{{tracks[trackCount].name}}</h1>
          <h2>{{tracks[trackCount].artistName}}</h2>
        </div>
      </div>
    </div>

    <div class="to-bottom">
      <div class="progress-bar">
        <span :style="{ width: trackProgress + '%' }"></span>
      </div>
      <div class="controls">
        <div class="navigate navigate-prev" :class="{'disabled' : trackCount == 0}" @click="prevTrack">
          <i class="fa fa-step-backward"></i>
        </div>
        <div class="navigate navigate-play" @click="playPause">
          <i v-show="!isPlaying" class="fa fa-play"></i>
          <i v-show="isPlaying" class="fa fa-pause"></i>
        </div>
        <div class="navigate navigate-next" :class="{'disabled' : trackCount == tracks.length - 1}" @click="nextTrack">
          <i class="fa fa-step-forward"></i>
        </div>
      </div>
    </div>
  </div>
</div>

问题

由于我无法弄清楚的原因，样式未绑定(bind)到 progress-bar 中的 span 元素。

我错过了什么？

---

更新

在 created 钩子(Hook)中使用 setInterval 有效，但我宁愿避免它？

this.player.addEventListener("loadedmetadata", () => {
  setInterval(() => {
    this.trackProgress =
      (this.player.currentTime / this.player.duration) * 100;
  }, 100);
});

什么是更好的选择？

Answer 1

求解过程说明:

1. 为播放器的timeupdate 事件设置监听器
2. 在 timeupdate 触发时更新组件的 data
3. 使用 percentageProgress 计算属性来计算进度并在模板中使用它。 (您仍然可以使用 trackProgress 属性，但 percentageProgress 在语义上更清晰一些。)

实现:

data() {
  return {
    player: new Audio(),
    trackCount: 0,
    tracks: [],
    muted: false,
    isPlaying: false,
    currentTime: 0
  };
},

computed: {
  percentageProgress() {
    return (this.currentTime / this.player.duration) * 100;
  }
}

created() {
  this.player.addEventListener("timeupdate", () => {
    this.currentTime = this.player.currentTime;
  });
}

另一方面，计算得到的 getter 必须返回一个值。您的计算属性不返回任何内容。