使用Android打印框架显示PDF文件打印视图时出现问题

Question

我已按照此sample code通过从我的文件系统传递现有PDF来显示打印视图。但我注意到它无法在打印视图中显示所有PDF。

PdfDocumentAdapter.java

public class PdfDocumentAdapter extends PrintDocumentAdapter {

Context context = null;
String pathName = "";
public PdfDocumentAdapter(Context ctxt, String pathName) {
    context = ctxt;
    this.pathName = pathName;
}
@Override
public void onLayout(PrintAttributes printAttributes, PrintAttributes printAttributes1, CancellationSignal cancellationSignal, LayoutResultCallback layoutResultCallback, Bundle bundle) {
    if (cancellationSignal.isCanceled()) {
        layoutResultCallback.onLayoutCancelled();
    }
    else {
        PrintDocumentInfo.Builder builder=
                new PrintDocumentInfo.Builder(" file name");
        builder.setContentType(PrintDocumentInfo.CONTENT_TYPE_DOCUMENT)
                .setPageCount(PrintDocumentInfo.PAGE_COUNT_UNKNOWN)
                .build();
        layoutResultCallback.onLayoutFinished(builder.build(),
                !printAttributes1.equals(printAttributes));
    }
}

@Override
public void onWrite(PageRange[] pageRanges, ParcelFileDescriptor parcelFileDescriptor, CancellationSignal cancellationSignal, WriteResultCallback writeResultCallback) {
    InputStream in=null;
    OutputStream out=null;
    try {
        File file = new File(pathName);
        in = new FileInputStream(file);
        out=new FileOutputStream(parcelFileDescriptor.getFileDescriptor());

        byte[] buf=new byte[16384];
        int size;

        while ((size=in.read(buf)) >= 0
                && !cancellationSignal.isCanceled()) {
            out.write(buf, 0, size);
        }

        if (cancellationSignal.isCanceled()) {
            writeResultCallback.onWriteCancelled();
        }
        else {
            writeResultCallback.onWriteFinished(new PageRange[] { PageRange.ALL_PAGES });
        }
    }
    catch (Exception e) {
        writeResultCallback.onWriteFailed(e.getMessage());
        Logger.logError( e);
    }
    finally {
        try {
            in.close();
            out.close();
        }
        catch (IOException e) {
            Logger.logError( e);
        }
    }
}
}

通过PrintManager调用它

PrintManager printManager=(PrintManager) SurefoxBrowserScreen.getActivityContext().getSystemService(Context.PRINT_SERVICE);
try
{
    PrintDocumentAdapter printAdapter = new PdfDocumentAdapter(Settings.sharedPref.context,filePath );
    }
    printManager.print("Document", printAdapter,new PrintAttributes.Builder().build());
}
catch (Exception e)
{
    Logger.logError(e);
}

此代码无法显示此PDF，它会加载空白页面而不包含任何内容。 https://www.scala-lang.org/old/sites/default/files/linuxsoft_archives/docu/files/ScalaByExample.pdf

但它适用于此PDF： https://www.tutorialspoint.com/scala/scala_tutorial.pdf。

我已检查过不同的PDF。其中一些正在运作，一些则没有。 我该如何解决这个问题？