[英]Swift2 retrieving images from Firebase
我正在嘗試從Firebase中讀取/顯示圖像。 我首先編碼圖像,然后將此編碼的字符串發布到Firebase。 這很好。 當我嘗試從Firebase解碼編碼的字符串並將其轉換為圖像時,我得到一個零值異常。
這就是我將圖像保存到Firebase的方式
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!")
}
這就是我嘗試從Firebase讀取圖像的方法
// 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.
}
}
錯誤說:“致命錯誤:在展開Optional值時意外發現nil”; decodingData是零。 有人可以解釋出了什么問題。
代替
let decodedData = NSData(base64EncodedString: self.base64String as String,
options: NSDataBase64DecodingOptions())
嘗試添加IgnoreUnknownCharacters
NSDataBase64DecodingOptions.IgnoreUnknownCharacters
使用示例:編碼jpg,存儲和讀取firebase
編碼並寫下我們最喜歡的星艦
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)
讀取和解碼
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)
})
編輯2019_05_17
更新到Swift 5和Firebase 6
func writeImage() {
if let image = NSImage(named:"Enterprise.jpg") {
let imageData = image.tiffRepresentation
if let base64String = imageData?.base64EncodedString() {
let imageRef = self.ref.child("image_path")
imageRef.setValue(base64String)
}
}
}
func readImage() {
let imageRef = self.ref.child("image_path")
imageRef.observeSingleEvent(of: .value, with: { snapshot in
let base64EncodedString = snapshot.value as! String
let imageData = Data(base64Encoded: base64EncodedString, options: Data.Base64DecodingOptions.ignoreUnknownCharacters)!
let decodedImage = NSImage(data: imageData)
self.myImageView.image = decodedImage
})
}
Firebase工程師在這里:
我強烈建議您使用新的Firebase存儲 API將圖像上傳到Firebase。 它使用簡單,成本低,並且大規模支持Google雲端存儲 。
您可以從NSData
或指向本地文件的NSURL
上傳(我將顯示NSData
,但原理是相同的):
// Data in memory
let data: NSData = ...
// Create a reference to the file you want to upload
let riversRef = storageRef.child("images/rivers.jpg")
// Upload the file to the path "images/rivers.jpg"
let uploadTask = riversRef.putData(data, metadata: nil) { metadata, error in
if (error != nil) {
// Uh-oh, an error occurred!
} else {
// Metadata contains file metadata such as size, content-type, and download URL.
let downloadURL = metadata!.downloadURL
// This can be stored in the Firebase Realtime Database
// It can also be used by image loading libraries like SDWebImage
}
}
您甚至可以暫停和恢復上傳,並可以輕松監控上傳進度:
// Upload data
let uploadTask = storageRef.putData(...)
// Add a progress observer to an upload task
uploadTask.observeStatus(.Progress) { snapshot in
// Upload reported progress
if let progress = snapshot.progress {
let percentComplete = 100.0 * Double(progress.completedUnitCount) / Double(progress.totalUnitCount)
}
}
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