Type mismatch: cannot convert from ByteMatrix to BitMatrix

问题

I am creating a QR code generator program in JAVA using ZXING library. The program is

import com.google.zxing.BarcodeFormat;
import com.google.zxing.WriterException;
import com.google.zxing.client.j2se.MatrixToImageWriter;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.qrcode.QRCodeWriter;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;


public class QR_Gen {
    private static final String QR_CODE_IMAGE_PATH = "./MyCode.png";

    private static void generateQRCodeImage(String text, int width, int 
height, String filePath) throws WriterException, IOException {
        QRCodeWriter qrCodeWriter = new QRCodeWriter();
        BitMatrix bitMatrix = qrCodeWriter.encode(text, 
BarcodeFormat.QR_CODE, width, height);
        Path path = FileSystems.getDefault().getPath(filePath);
        MatrixToImageWriter.writeToPath(bitMatrix, "PNG", path);

    }
    public static void main(String[] args) {
        try {
            generateQRCodeImage("This is my first QR Code", 350, 350, QR_CODE_IMAGE_PATH);
            System.out.println("QR Code generated successfully");
        } catch (WriterException e) {

            System.out.println("Could not generate QR Code, WriterException :: " + e.getMessage());
        } catch (IOException e) {
            System.out.println("Could not generate QR Code, IOException :: " + e.getMessage());
        }
    }

}

While compiling this program i'm getting a Type Mismatch Error,

Type mismatch: cannot convert from ByteMatrix to BitMatrix

in this line

BitMatrix bitMatrix = qrCodeWriter.encode(text, BarcodeFormat.QR_CODE, width, height);

Please help!!!

回答1:

Never used this library myself, but reading the errormessage I would assume that you have to problem that you want to store byte in bits. The problem will be that a byte is build up by multiple bits so you cannot represent a byte via only one bit.

Store your encode data into an ByteMatrix and then read this post:

QR Code encoding and decoding using zxing

to finish things off.

回答2:

According to the javadoc here and the source code here, the QRCodeWriter.encode methods return a BitMatrix, not a ByteMatrix. So, that compilation error should not occur.

Unless ....

... you are using some version¹ of the com.google.zxing library that is incompatible with those javadocs. Check where you got your zxing JAR file from.

Despite searching, I haven't been able to find the version with this incompatibility. However:

I note that the official library has been forked many times on GitHub, and any one of those could be the source of the incompatibility.
I found this which clearly a fork, and clearly has tweaked encode. However, the people who did this have at least had the good sense to change the package name!

I don't know if this is relevant, but it appears that in the C# version of this API, the QRCodeWriter.encode method does return a ByteMatrix; see here for evidence. Maybe you've stumbled across someone's misguided attempt to "fix" the Java API to match the C# API.

回答3:

I got the same Issues and i solve it by downloading compatible zxing-javase.jar and zxing

http://www.java2s.com/Code/Jar/z/Downloadzxingjavasejar.htm http://www.java2s.com/Code/Jar/z/Downloadzxingjar.htm

the latest version are compatible and use ByteMatrix not BitMatrix. download them from original www.java2s.com

来源：https://stackoverflow.com/questions/51763384/type-mismatch-cannot-convert-from-bytematrix-to-bitmatrix

标签

java

zxing

type-mismatch