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 metadata) {
 // 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 framework
  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 framework
  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 ParcelFileDescriptor 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.getFileDescriptor()));
 } catch (IOException e) {
  callback.onWriteFailed(e.toString());
  return;
 } finally {
  mPdfDocument.close();
  mPdfDocument = null;
 }
 PageRange[] writtenPages = computeWrittenPages();
 // Signal the print framework 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 titleBaseLine = 72;
 int leftMargin = 54;
 
 Paint paint = new Paint();
 paint.setColor(Color.BLACK);
 paint.setTextSize(36);
 canvas.drawText("Test Title", leftMargin, titleBaseLine, paint);
 
 paint.setTextSize(11);
 canvas.drawText("Test paragraph", leftMargin, titleBaseLine + 25, paint);
 
 paint.setColor(Color.BLUE);
 canvas.drawRect(100, 100, 172, 172, paint);
}