如何等到图像上传到 Ionic 2 中的 firebase 存储

How to wait until image uploaded to firebase storage in Ionic 2

我正在尝试使用加载程序等到图像上传到 firebase 存储,但效果不佳

我的代码是这样写的,但我不知道我的错误在哪里,为什么在上传过程之前显示警报。

private uploadPhoto(): void {
    let loader = this.loadingCtrl.create({
        content: ""
    })
    loader.present().then(_=>{
        this.myPhotosRef.child(this.generateUUID()).child('myPhoto.JPEG')
        .putString(this.myPhoto, 'base64', { contentType: 'image/JPEG' })
        .then((savedPicture) => {
            this.myPhotoURL = savedPicture.downloadURL;
            this.afd.list('/Images/').push({
                nID: this.appService.id,
                url: this.myPhotoURL,
                date: new Date().toISOString()
            });
        });
    }).then(_=>{
        alert("image uploaded and stored in database");
        loader.dismiss();
    })
}

我通过在 "this.myPhotosRef.child..."

之前添加 "return" 得到了解决方案