如何将base64转换为pdf？

Question

如何将一个base64输入转换为Android中的PDF文件？

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = this;
        setContentView(R.layout.activity_main);
        // Get the PDF file to encode it into Base64
        File file = new File("/mnt/sdcard/download/Base64.pdf");
        try {
            // Files is from Guava library
            Files.toByteArray(file);
            // Encoded into Base64
            byte[] temp = Base64.encode(Files.toByteArray(file), Base64.DEFAULT);
            // For testing purposes, wrote the encoded string to file
            writeToFile(Base64.encodeToString(temp, Base64.DEFAULT).toString());

        } catch (IOException e) {
            Log.d(tag, "File.toByteArray() error");
            e.printStackTrace();
        }
    }

我能够使用http://www.webutils.pl/index.php?idx=base64来测试PDF文件是否被正确编码。但我想自己解码base64为PDF文件。我该怎么做？ 编辑1 尝试了Saneesh CS建议的以下代码。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = this;
        setContentView(R.layout.activity_main);
        // Get the PDF file to encode it into Base64
        File file = new File("/mnt/sdcard/download/Base64.pdf");
        try {
            // Files is from Guava library
            Files.toByteArray(file);
            // Encoded into Base64
            byte[] temp = Base64.encode(Files.toByteArray(file), Base64.DEFAULT);
            // Tried with the below line, but same result.
            byte[] temp1 = Base64.encode(Files.toByteArray(file), 0);
            // For testing purposes, wrote the encoded string to file
//          writeToFile(Base64.encodeToString(temp, Base64.DEFAULT).toString());
            final File dwldsPath = new File(Environment.getExternalStorageDirectory(), "test7.pdf");
            byte[] pdfAsBytes = Base64.decode(temp, 0);
            FileOutputStream os;
            os = new FileOutputStream(dwldsPath, false);
            os.write(pdfAsBytes);
            os.flush();
            os.close();
        } catch (IOException e) {
            Log.d(tag, "File.toByteArray() error");
            e.printStackTrace();
        }
    }

以上代码有效。

- Noman Arain

---

编辑1中的代码进行编码，而非解码。 - Henry

谢谢，你发现得真好。现在它能用了。 - Noman Arain

Answer 1

final File dwldsPath = new File(DOWNLOADS_FOLDER + fileName + ".pdf");
byte[] pdfAsBytes = Base64.decode(txt, 0);
FileOutputStream os;
os = new FileOutputStream(dwldsPath, false);
os.write(pdfAsBytes);
os.flush();
os.close();

尝试使用这段代码。txt是base64编码的字符串。

- San

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要将文件保存在/storage/emulated/0/Download中，请将DOWNLOADS_FOLDER更改为Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/"。 - alditis

Answer 2

这段代码可能对您有帮助。我已经执行了附加的代码，它完美地运行。

public static GetFilePathAndStatus getFileFromBase64AndSaveInSDCard(String base64, String filename,String extension){
    GetFilePathAndStatus getFilePathAndStatus = new GetFilePathAndStatus();
    try {
        byte[] pdfAsBytes = Base64.decode(base64, 0);
        FileOutputStream os;
        os = new FileOutputStream(getReportPath(filename,extension), false);
        os.write(pdfAsBytes);
        os.flush();
        os.close();
        getFilePathAndStatus.filStatus = true;
        getFilePathAndStatus.filePath = getReportPath(filename,extension);
        return getFilePathAndStatus;
    } catch (IOException e) {
        e.printStackTrace();
        getFilePathAndStatus.filStatus = false;
        getFilePathAndStatus.filePath = getReportPath(filename,extension);
        return getFilePathAndStatus;
    }
}

public static String getReportPath(String filename,String extension) {
    File file = new File(Environment.getExternalStorageDirectory().getPath(), "ParentFolder/Report");
    if (!file.exists()) {
        file.mkdirs();
    }
    String uriSting = (file.getAbsolutePath() + "/" + filename + "."+extension);
    return uriSting;

}
public static class GetFilePathAndStatus{
    public boolean filStatus;
    public String filePath;

}

- Sufiyan Ansari

Answer 3

这个解决方案在Kotlin上对我有效

private fun setPdfDownload(bill: BillDataPdfOutput){
    if (bill.data != null) {

        val file = File(getFilePath("pdf_name"))

        try {
            FileOutputStream(file).use { fos ->
                val decoder = Base64.getDecoder().decode(bill.data)
                fos.write(decoder)
                Toast.makeText(this, "downloading success", Toast.LENGTH_LONG).show()
            }
        } catch (e: Exception) {
            e.printStackTrace()
        }


    }else {
        Log.v("PDF", "not download " + bill.message)
    }
}

fun getFilePath(filename: String): String {
    val file =
        File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).path)
    if (!file.exists()) {
        file.mkdirs()
    }
    return file.absolutePath.toString() + "/" + filename + ".pdf"
}

- Danny Escalante

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