如何从文件中获取ByteData

问题描述

我想在Flutter中将 File 转换为 ByteData 对象.像这样:

I want to convert a File to a ByteData object in flutter.Something like this:

import 'dart:io';
File file = getSomeCorrectFile(); //This file is correct
ByteData bytes = ByteData(file.readAsBytesSync()); //Doesnt compile
return bytes;

我了解到 ByteData 构造函数接收字节长度的长度并将其初始化为0，所以我可以做类似 ByteData(file.readAsBytesStync().length); ，但是我该如何填充它们?我想念什么?

I understood that ByteData constructor receives the length of the amount of bytes and initialize them with 0, so I could do something like ByteData(file.readAsBytesStync().length); but then how do I fill them?What am I missing?

推荐答案

在Dart 2.5.0或更高版本中，我认为以下方法应该有效:

In Dart 2.5.0 or later, I believe that the following should work:

import 'dart:io';
import 'dart:typed_data';

...
File file = getSomeCorrectFile();
Uint8List bytes = file.readAsBytesSync();
return ByteData.view(bytes.buffer);

(在Dart 2.5.0之前， file.readAsBytesSync()行应为:

(Prior to Dart 2.5.0, the file.readAsBytesSync() line should be:

Uint8List bytes = file.readAsBytesSync() as Uint8List;

File.readAsBytes / File.readAsBytesSync 曾经被声明为返回 List< int> ，但是返回的对象实际上是 Uint8List 子类型.)

File.readAsBytes/File.readAsBytesSync used to be declared to return a List<int>, but the returned object was actually a Uint8List subtype.)

将字节作为 Uint8List 后，您可以提取其 ByteBuffer 并从中构造一个 ByteData .

Once you have the bytes as a Uint8List, you can extract its ByteBuffer and construct a ByteData from that.

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