Android实现系统打印功能

private void doPhotoPrint() {
  PrintHelper photoPrinter = new PrintHelper(getActivity());
  photoPrinter.setScaleMode(PrintHelper.SCALE_MODE_FIT);
  Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
      R.drawable.droids);
  photoPrinter.printBitmap(\"droids.jpg - test print\", bitmap);
}

private void doPrint() {
  // Get a PrintManager instance
  PrintManager printManager = (PrintManager) getActivity()
      .getSystemService(Context.PRINT_SERVICE);
 
  // Set job name, which will be displayed in the print queue
  String jobName = getActivity().getString(R.string.app_name) + \" Document\";
 
  // Start a print job, passing in a PrintDocumentAdapter implementation
  // to handle the generation of a print document
  printManager.print(jobName, new MyPrintDocumentAdapter(getActivity()),
      null); //
}

@Override
public void onLayout(PrintAttributes oldAttributes,
           PrintAttributes newAttributes,
           CancellationSignal cancellationSignal,
           LayoutResultCallback callback,
           Bundle  data) {
  // Create a new PdfDocument with the requested page attributes
  mPdfDocument = new PrintedPdfDocument(getActivity(), newAttributes);
 
  // Respond to cancellation request
  if (cancellationSignal.isCancelled() ) {
    callback.onLayoutCancelled();
    return;
  }
 
  // Compute the expected number of printed pages
  int pages = computePageCount(newAttributes);
 
  if (pages > 0) {
    // Return print information to print  work
    PrintDocumentInfo info = new PrintDocumentInfo
        .Builder(\"print_output.pdf\")
        .setContentType(PrintDocumentInfo.CONTENT_TYPE_DOCUMENT)
        .setPageCount(pages);
        .build();
    // Content layout reflow is complete
    callback.onLayoutFinished(info, true);
  } else {
    // Otherwise report an error to the print  work
    callback.onLayoutFailed(\"Page count calculation failed.\");
  }
}

onLayout()方法的主要任务就是计算在新的设置下，需要打印的页数，如通过打印的方向决定页数：
private int computePageCount(PrintAttributes printAttributes) {
  int itemsPerPage = 4; // default item count for portrait mode
 
  MediaSize pageSize = printAttributes.getMediaSize();
  if (!pageSize.isPortrait()) {
    // Six items per page in landscape orientation
    itemsPerPage = 6;
  }
 
  // Determine number of print items
  int printItemCount = getPrintItemCount();
 
  return (int) Math.ceil(printItemCount / itemsPerPage);
}

@Override
public void onWrite(final PageRange[] pageRanges,
          final ParcelFileDe or destination,
          final CancellationSignal cancellationSignal,
          final WriteResultCallback callback) {
  // Iterate over each page of the document,
  // check if it\'s in the output range.
  for (int i = 0; i < totalPages; i++) {
    // Check to see if this page is in the output range.
    if (containsPage(pageRanges, i)) {
      // If so, add it to writtenPagesArray. writtenPagesArray.size()
      // is used to compute the next output page index.
      writtenPagesArray.append(writtenPagesArray.size(), i);
      PdfDocument.Page page = mPdfDocument.startPage(i);
 
      // check for cancellation
      if (cancellationSignal.isCancelled()) {
        callback.onWriteCancelled();
        mPdfDocument.close();
        mPdfDocument = null;
        return;
      }
 
      // Draw page content for printing
      drawPage(page);
 
      // Rendering is complete, so page can be finalized.
      mPdfDocument.finishPage(page);
    }
  }
 
  // Write PDF document to file
  try {
    mPdfDocument.writeTo(new FileOutputStream(
        destination.getFileDe or()));
  } catch (IOException e) {
    callback.onWriteFailed(e.toString());
    return;
  } finally {
    mPdfDocument.close();
    mPdfDocument = null;
  }
  PageRange[] writtenPages = computeWrittenPages();
  // Signal the print  work the document is complete
  callback.onWriteFinished(writtenPages);
 
  ...
}

private void drawPage(PdfDocument.Page page) {
  Canvas canvas = page.getCanvas();
 
  // units are in points (1/72 of an inch)
  int   Line = 72;
  int leftMargin = 54;
 
  Paint paint = new Paint();
  paint.setColor(Color.BLACK);
  paint.setTextSize(36);
  canvas.drawText(\"Test  \", leftMargin,   Line, paint);
 
  paint.setTextSize(11);
  canvas.drawText(\"Test paragraph\", leftMargin,   Line + 25, paint);
 
  paint.setColor(Color.BLUE);
  canvas.drawRect(100, 100, 172, 172, paint);
}