在 Android 上創建 Cloud Storage 參考

您的文件存儲在雲存儲桶。此存儲分區中的文件以分層結構呈現,就像本地硬盤上的文件系統或 Firebase 實時數據庫中的數據一樣。通過創建對文件的引用,您的應用程序可以訪問它。然後可以使用這些引用來上傳或下載數據、獲取或更新元數據或刪除文件。引用可以指向特定文件或層次結構中的更高級別節點。

如果您已經使用了火力地堡實時數據庫,這些路徑應該在你看來很熟悉。然而,你的文件數據存儲在雲存儲,而不是在實時數據庫。

創建參考

創建引用以上傳、下載或刪除文件,或者獲取或更新其元數據。可以將引用視為指向雲中文件的指針。引用是輕量級的,因此您可以根據需要創建任意數量的引用。它們也可重複用於多項操作。

創建使用一個參考FirebaseStorage單一實例並調用其getReference()方法。

爪哇

// Create a storage reference from our app
StorageReference storageRef = storage.getReference();

科特林+KTX

// Create a storage reference from our app
var storageRef = storage.reference

接下來,你可以在樹中創建一個位置的參考下,說"images/space.jpg"使用child()方法對現有的參考。

爪哇

// Create a child reference
// imagesRef now points to "images"
StorageReference imagesRef = storageRef.child("images");

// Child references can also take paths
// spaceRef now points to "images/space.jpg
// imagesRef still points to "images"
StorageReference spaceRef = storageRef.child("images/space.jpg");

科特林+KTX

// Create a child reference
// imagesRef now points to "images"
var imagesRef: StorageReference? = storageRef.child("images")

// Child references can also take paths
// spaceRef now points to "images/space.jpg
// imagesRef still points to "images"
var spaceRef = storageRef.child("images/space.jpg")

您還可以使用getParent()getRoot()方法在我們的文件層次結構進行導航了。 getParent()導航一個級別,而getRoot()導航一路頂部。

爪哇

// getParent allows us to move our reference to a parent node
// imagesRef now points to 'images'
imagesRef = spaceRef.getParent();

// getRoot allows us to move all the way back to the top of our bucket
// rootRef now points to the root
StorageReference rootRef = spaceRef.getRoot();

科特林+KTX

// parent allows us to move our reference to a parent node
// imagesRef now points to 'images'
imagesRef = spaceRef.parent

// root allows us to move all the way back to the top of our bucket
// rootRef now points to the root
val rootRef = spaceRef.root

child() getParent()getRoot()可以多次鏈接在一起,因為每一個返回的參考。但調用getRoot().getParent()返回null

爪哇

// References can be chained together multiple times
// earthRef points to 'images/earth.jpg'
StorageReference earthRef = spaceRef.getParent().child("earth.jpg");

// nullRef is null, since the parent of root is null
StorageReference nullRef = spaceRef.getRoot().getParent();

科特林+KTX

// References can be chained together multiple times
// earthRef points to 'images/earth.jpg'
val earthRef = spaceRef.parent?.child("earth.jpg")

// nullRef is null, since the parent of root is null
val nullRef = spaceRef.root.parent

參考屬性

您可以檢查引用,以更好地它們指向的文件,了解使用getPath() getName()getBucket()方法。這些方法獲取文件的完整路徑、名稱和存儲桶。

爪哇

// Reference's path is: "images/space.jpg"
// This is analogous to a file path on disk
spaceRef.getPath();

// Reference's name is the last segment of the full path: "space.jpg"
// This is analogous to the file name
spaceRef.getName();

// Reference's bucket is the name of the storage bucket that the files are stored in
spaceRef.getBucket();

科特林+KTX

// Reference's path is: "images/space.jpg"
// This is analogous to a file path on disk
spaceRef.path

// Reference's name is the last segment of the full path: "space.jpg"
// This is analogous to the file name
spaceRef.name

// Reference's bucket is the name of the storage bucket that the files are stored in
spaceRef.bucket

參考文獻的限制

引用路徑和名稱可以包含任何有效 Unicode 字符序列,但會施加某些限制,包括:

  1. UTF-8 編碼時,reference.fullPath 的總長度必須在 1 到 1024 字節之間。
  2. 沒有回車符或換行符。
  3. 避免使用#[]*? ,因為這些不與其他工具,如很好地工作火力地堡實時數據庫gsutil會

完整示例

爪哇

// Points to the root reference
storageRef = storage.getReference();

// Points to "images"
imagesRef = storageRef.child("images");

// Points to "images/space.jpg"
// Note that you can use variables to create child values
String fileName = "space.jpg";
spaceRef = imagesRef.child(fileName);

// File path is "images/space.jpg"
String path = spaceRef.getPath();

// File name is "space.jpg"
String name = spaceRef.getName();

// Points to "images"
imagesRef = spaceRef.getParent();

科特林+KTX

// Points to the root reference
storageRef = storage.reference

// Points to "images"
imagesRef = storageRef.child("images")

// Points to "images/space.jpg"
// Note that you can use variables to create child values
val fileName = "space.jpg"
spaceRef = imagesRef.child(fileName)

// File path is "images/space.jpg"
val path = spaceRef.path

// File name is "space.jpg"
val name = spaceRef.name

// Points to "images"
imagesRef = spaceRef.parent

接下來,讓我們學習如何上傳文件到雲存儲。