我从不同的来源(电话,Google驱动器等本地)获取PDF的URI,对于DropBox,我可以使用URI作为输入来读取字节数组.但是我得到的PDF不是有效的PDF. Base64也不正确.
这是我的URI：
内容：//com.dropBox.android.FileCache/filecache/a54cc030-e2e0-4ef5-8e72-0ac3269a16e1
val inputStream = context.contentResolver.openInputStream(Uri.parse(uri))
val allText = inputStream.bufferedReader().use(BufferedReader::readText)
val base64Image = Base64.encodeToString(allText.toByteArray(),Base64.DEFAULT)
%PDF-1.3
%���������
4 0 obj
<< /Length 5 0 R /Filter /FlateDecode >>
.
.
.
13025
%%EOF
当存储带有.PDF扩展名的allText内容时,该功能不起作用.
格式看起来不错,但是当在https://base64.guru/converter/decode/pdf中插入base64Image时,表明它是不正确的.
2550 4446 2d31 2e33 0a25 c4e5 f2e5 eba7
f3a0 d0c4 c60a 3420 3020 6f62 6a0a 3c3c
.
.
.
.
0a73 7461 7274 7872 6566 0a31 3330 3235
0a25 2545 4f46 0a
“I can read a byte array using the URI as input. But the PDF that I’m getting is not a valid PDF.”
“When storing the
allTextcontent with .PDF extension doesn’t work.”
您正在读取PDF输入字节(十六进制)并将其存储为错误的格式(文本).
例如,所有有效的PDF文件都应以字节25 50 44 46开头.您的allText内容片段以％PDF开头,％PDF是这些字节的转换后的ASCII / UTF文本表示形式.
问题：
所有这些都很好,因为我们可以将文本字符转换回各自的字节值,对吗？不,并非所有字节值都可以从文本格式正确恢复.
范例1：可以转换…
input bytes : 25 50 44 46
as text : % P D F
into bytes : 25 50 44 46
示例#2：无法转换(由于这些字节没有文本字符,因此无法恢复原始数据)…
input bytes : 25 C4 E5 F2 E5 EB A7 F3 A0 D0
as text : % � � � � � � � � �
into bytes : 25 00 00 00 00 00 00 00 00 00
解：
import java.io.File
import java.io.InputStream
fun main(args: Array<String>)
{
//# setup access to your file...
var inFile :InputStream = File("your-file-path-here.pdf")
var fileSize :Int = File(path).length()
//# read file bytes into a bytes Array...
var inStream :InputStream = inFile.inputStream()
var inBytes :ByteArray = inStream.readBytes()
//# Make as String (of hex values)...
//var hexString :String = ""
val hexString = ""
for (b in inBytes) { hexString = String.format("%02X",b) }
//# check values as hex... should print: 25
//print(hexString) //could be long print-out for a big file
//# Make Base64 string...
val base64 = Base64.getEncoder().encodeToString(inBytes)
}
“Base64 is also not correct.”
(选项1)
尝试将上述示例代码中的hexString转换为Base64(注意：现在已添加为val base64).
(选项2)
使用简单的…直接将文件字节读取为Base64字符串
val bytes = File(filePath).readBytes()
val base64 = Base64.getEncoder().encodeToString(bytes)
