从 firebase 存储下载 url 为空

Question

我正在使用 ionic 4 将图像从相机上传到 Firebase 存储。上传顺利，但我很难获得上传 URL。我的代码如下所示：

async getFromCamera(){
    this.camera.getPicture({
      destinationType: this.camera.DestinationType.DATA_URL,
      quality: 25,
      correctOrientation: true,
        allowEdit:false
  }).then(async (imageData) => {
      var base64Image = "data:image/jpeg;base64," + imageData;
      this.uploadToFireStore(base64Image).then(
            (data) => console.log("done to firestore:"  + data),
            (err) => console.log("The error to upload is:::" + JSON.stringify(err))
          )
  }, (err) => {
      console.log("Error found is:" + err);
  });
  }

  uploadPercent
  downloadURL

  uploadToFireStore(imageData){
   return new Promise<any>((resolve, reject) => {
    let storageRef = this.storage.ref('/');
    let imageRef = storageRef.child('myimage')
    const task = imageRef.putString(imageData, 'data_url')

      console.log("Task is:::" + task)
       // observe percentage changes
    this.uploadPercent = task.percentageChanges();
    // get notified when the download URL is available
    task.snapshotChanges().pipe(
        finalize(() => {
                            this.downloadURL = imageRef.getDownloadURL() 
                            console.log("upload percent:" + JSON.stringify(this.uploadPercent))
                            console.log("download url is::" + JSON.stringify(this.downloadURL))
                      } 
                )
     )
    .subscribe()
  })
  }

我看到的回应是：

upload percent:{"_isScalar":false,"source":{"_isScalar":false},"operator":{}}
/tab1-tab1-module.js:629 download url is::{"_isScalar":false}

Answer 1

Firebase 存储可让您上传文件，因此您无需上传很长的 base64 字符串。为什么还要上传base64？

我不熟悉this.camera.getPicture 方法返回的内容，但很确定它是File 的一种类型。在这种情况下：

}).then(imageData => {
    this.uploadToFireStore(imageData)

和

  uploadToFireStore(imageData){
    let storageRef = this.storage.ref('/');
    let imageRef = storageRef.child('myimage')
    const task = imageRef.upload(imageData, 'data_url')

    this.uploadPercent = task.percentageChanges();
    task.snapshotChanges().pipe(
        finalize( async () => {
          await this.downloadURL = imageRef.getDownloadURL().toPromise();
          console.log('this.downloadURL', this.downloadURL)

                      } 
                )
     )
    .subscribe()

注意finalize 采用async 函数，因为imageRef.getDownloadURL() 返回一个Observable，所以我们只需要一个值，这是我们需要的唯一值，转换它看起来更简洁承诺。