Brother SDK Calling PrintImage causes JNI DETECTED ERROR IN APPLICATION: GetStringUTFChars received NULL jstring

Question

Currently working with the Brother SDK for a label Printer and when I call Asset Manager, the Bitmap appears but when it is parsed to print image it crashes.

if (myPrinter.startCommunication()) {
AssetManager assetManager = getAssets();
          Bitmap bitmap = null;
          try{
              bitmap = BitmapFactory.decodeStream(new BufferedInputStream(assetManager.open("meme.bmp")));
             }catch(Exception e){
               e.printStackTrace();
             }
          PrinterStatus result = myPrinter.printImage(bitmap);
       if (result.errorCode != ErrorCode.ERROR_NONE) {
         Log.d("TAG", "ERROR - " + result.errorCode);
       }
         myPrinter.endCommunication();
}

Stack Readout

Debugger printout, with Image Preview.

I added the debugger printout, the image is there for preview, but it is null so not sure what is going on. — Felix Hu, Feb 14 '20 at 00:29
Time to look at the implementation of the method mentioned in the JNI error with a debugger. — Thorbjørn Ravn Andersen, Feb 14 '20 at 00:39
I tested the asset manager code section elsewhere in the code base and its also returning the same way as the debugger above. Is there another way of loading a bmp into the Bitmap datatype. — Felix Hu, Feb 14 '20 at 00:57

score 1 · Answer 1 · answered May 15 '20 at 11:53

For anyone got stuck even if they made sure they have the write permission granted, it was about the working path b-PAC trying to create.

The default path is: /storage/emulated/0/com.brother.ptouch.sdk/template

Just define your own path in PrinterInfo object. Set the workPath variable as such:

PrinterInfo mPrintSettings = mPrinter.getPrinterInfo();
mPrintSettings.workPath = "your/custom/work/path";

It says in the document that you don't even need the permission if you do so. But I'm going to keep it anyway.

This is awesome! Fixed our issue with our Brother printer not working with Android 10. Once I passed in a `workPath`, it started working again. Thanks so much! — Jarod Legault, Dec 01 '20 at 18:26

score 0 · Accepted Answer · answered Mar 28 '20 at 04:43

I had this issue as well. Have you made sure that the android.permission.WRITE_EXTERNAL_STORAGE permisson is granted. Having this in the manifest file wasn't enough, but by requesting permisson from the user, this specific error went away.

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Brother SDK Calling PrintImage causes JNI DETECTED ERROR IN APPLICATION: GetStringUTFChars received NULL jstring

2 Answers2