I used zxing-1.3 jar and I had to make some changes implementing code from other answers, so I will leave my solution for others. I did the following:
1) find zxing-1.3.jar, download it and add in properties (add external jar).
2) in my activity layout add ImageView and name it (in my example it was tnsd_iv_qr).
3) include code in my activity to create qr image (in this example I was creating QR for bitcoin payments):
QRCodeWriter writer = new QRCodeWriter();
ImageView tnsd_iv_qr = (ImageView)findViewById(R.id.tnsd_iv_qr);
try {
ByteMatrix bitMatrix = writer.encode("bitcoin:"+btc_acc_adress+"?amount="+amountBTC, BarcodeFormat.QR_CODE, 512, 512);
int width = 512;
int height = 512;
Bitmap bmp = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
if (bitMatrix.get(x, y)==0)
bmp.setPixel(x, y, Color.BLACK);
else
bmp.setPixel(x, y, Color.WHITE);
}
}
tnsd_iv_qr.setImageBitmap(bmp);
} catch (WriterException e) {
//Log.e("QR ERROR", ""+e);
}
If someone is wondering, variable "btc_acc_adress" is a String (with BTC adress), amountBTC is a double, with, of course, transaction amount.