Swift2从Firebase中检索图片 [英] Swift2 retrieving images from Firebase

问题描述

我试图从Firebase读取/显示图片。我首先编码图像，然后将这个编码的字符串发布到Firebase。这运行良好。当我尝试解码来自Firebase的编码字符串并将其转换为图像时，我得到一个零值异常。

这就是我将图像保存到Firebase

  var base64String：NSString！ 
 func imagePickerController（picker：UIImagePickerController，didFinishPickingImage image：UIImage，editingInfo：[String：AnyObject]？）{
 
 self.dismissViewControllerAnimated（true，completion：nil）
 
 imageToPost.image = image 
 
 var uploadImage = image as！ UIImage 
 var imageData = UIImagePNGRepresentation（uploadImage）！ 
 self.base64String = imageData.base64EncodedStringWithOptions（NSDataBase64EncodingOptions.Encoding64CharacterLineLength）
 let ref = Firebase（url：https://XXX.firebaseio.com）
 
 var quoteString = [string：self.base64String] 
 var usersRef = ref.childByAppendingPath（goalImages）
 var users = [image：quoteString] 
 usersRef.setValue（users）
 
 displayAlert（Image Posted，信息：Your image has been posted posted！）
} 
  

这就是我想要从Firebase读取图片的方式

  // ViewController.swift 
 
导入UIKit 
导入Firebase 
 
类ViewController：UIViewController {
 @IBOutlet弱var image：UIImageView！ 
 var base64String：NSString！ 
 
 @IBAction func buttonClicked（sender：AnyObject）{
 
 sender.setTitle（\（sender.tag），forState：UIControlState.Normal）
 
 
 $ b重写func viewDidLoad（）{
 super.viewDidLoad（）
 //在加载视图之后，通常从一个笔尖执行任何额外的设置。 
 
 let ref = Firebase（url：https://XXX.firebaseio.com/goalImages/image/string）
 
 ref.observeEventType（.Value，withBlock： {snapshot in 
 
 self.base64String = snapshot.value as！NSString 
 let decodedData = NSData（base64EncodedString：self.base64String as String，options：NSDataBase64DecodingOptions（））
 //下一行是错误
 var decodeImage = UIImage（data：decodedData！）
 
 self.image.image = decodedImage 
}，withCancelBlock：{error in 
 print（error.description）
}）
 
} 
 
覆盖func didReceiveMemoryWarning（）{
 super.didReceiveMemoryWarning（）
 //处置任何可以重新创建的资源。 
 
 
 
 
 
 
 
错误提示：致命错误：意外发现无同时展开一个可选值; decodeData是零。有人可以解释什么是错的。 
解决方案
  let decodedData = NSData（base64EncodedString：self.base64String as String，
 options：NSDataBase64DecodingOptions（））
  
 
 
尝试添加IgnoreUnknownCharacters  
 
 
  NSDataBase64DecodingOptions.IgnoreUnknownCharacters 
  
使用示例：编码一个jpg，存储并从firebase读取
 
编码并编写我们最喜欢的星舰
 
 
 $ p $ 如果let image = NSImage（named：Enterprise.jpeg）{
 let imageData = image.TIFFRepresentation 
 let base64String = imageData！.base64EncodedStringWithOptions（.Encoding64CharacterLineLength）
 let imageRef = myRootRef.childByAppendingPath（image_path）
 imageRef.setValue（base64String）
  

读取和解码

  imageRef.observeEventType（.V alue，withBlock：{快照
 
让base64EncodedString = snapshot.value 
让imageData = NSData（base64EncodedString：base64EncodedString as！字符串，
选项：NSDataBase64DecodingOptions.IgnoreUnknownCharacters）
让decodeImage = NSImage（data：imageData！）
 self.myImageView.image = decodedImage 
 
}，withCancelBlock：{错误
 print（error.description）
}）
  

I am trying to read/display an image from Firebase. I am first encoding the image and then posting this encoded String to Firebase. This runs fine. When I try and decode the encoded string from Firebase and convert it to an image, I am getting a nil value exception.

This is how I am saving the image to Firebase

var base64String: NSString!
func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage, editingInfo: [String : AnyObject]?) {

    self.dismissViewControllerAnimated(true, completion: nil)

    imageToPost.image = image

    var uploadImage = image as! UIImage
    var imageData = UIImagePNGRepresentation(uploadImage)!
    self.base64String = imageData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)
    let ref = Firebase(url: "https://XXX.firebaseio.com")

    var quoteString = ["string": self.base64String]
    var usersRef = ref.childByAppendingPath("goalImages")
    var users = ["image": quoteString]
    usersRef.setValue(users)

    displayAlert("Image Posted", message: "Your image has been successfully posted!")
}

This is how I am trying to read the image from Firebase

//  ViewController.swift

import UIKit
import Firebase

class ViewController: UIViewController {
@IBOutlet weak var image: UIImageView!
var base64String: NSString!

@IBAction func buttonClicked(sender: AnyObject) {

    sender.setTitle("\(sender.tag)", forState: UIControlState.Normal)

}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    let ref = Firebase(url: "https://XXX.firebaseio.com/goalImages/image/string")

    ref.observeEventType(.Value, withBlock: { snapshot in

        self.base64String = snapshot.value as! NSString
        let decodedData = NSData(base64EncodedString: self.base64String as String, options: NSDataBase64DecodingOptions())
        //Next line is giving the error
        var decodedImage = UIImage(data: decodedData!)

        self.image.image = decodedImage
        }, withCancelBlock: { error in
            print(error.description)
        })

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
}

The error says: "fatal error: unexpectedly found nil while unwrapping an Optional value"; decodedData is nil. Could someone explain what is going wrong.

解决方案

Instead of

let decodedData = NSData(base64EncodedString: self.base64String as String, 
                                     options: NSDataBase64DecodingOptions())

try adding IgnoreUnknownCharacters

NSDataBase64DecodingOptions.IgnoreUnknownCharacters

Use Example: Encode a jpg, store and read from firebase

encode and write our favorite star ship

    if let image = NSImage(named:"Enterprise.jpeg") {
    let imageData = image.TIFFRepresentation
    let base64String = imageData!.base64EncodedStringWithOptions(.Encoding64CharacterLineLength)
    let imageRef = myRootRef.childByAppendingPath("image_path")
    imageRef.setValue(base64String)

read and decode

       imageRef.observeEventType(.Value, withBlock: { snapshot in

            let base64EncodedString = snapshot.value
            let imageData = NSData(base64EncodedString: base64EncodedString as! String, 
                           options: NSDataBase64DecodingOptions.IgnoreUnknownCharacters)
            let decodedImage = NSImage(data:imageData!)
            self.myImageView.image = decodedImage

            }, withCancelBlock: { error in
                print(error.description)
        })

这篇关于Swift2从Firebase中检索图片的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！