Android预览pdf文档

/**
 * Creates a new instance.
 * <p>
 * <strong>Note:</strong> The provided file descriptor must be <strong>seekable</strong>,
 * i.e. its data being randomly accessed, e.g. pointing to a file.
 * </p>
 * <p>
 * <strong>Note:</strong> This class takes ownership of the passed in file descriptor
 * and is responsible for closing it when the renderer is closed.
 * </p>
 * <p>
 * If the file is from an untrusted source it is recommended to run the renderer in a separate,
 * isolated process with minimal permissions to limit the impact of security exploits.
 * </p>
 *
 * @param input Seekable file descriptor to read from.
 *
 * @throws java.io.IOException If an error occurs while reading the file.
 * @throws java.lang.SecurityException If the file requires a password or
 *         the security scheme is not supported.
 */
public PdfRenderer(@NonNull ParcelFileDescriptor input){
  //略...
}

/**
   * Create a new ParcelFileDescriptor accessing a given file.
   *
   * @param file The file to be opened.
   * @param mode The desired access mode, must be one of
   *            {@link #MODE_READ_ONLY}, {@link #MODE_WRITE_ONLY}, or
   *            {@link #MODE_READ_WRITE}; may also be any combination of
   *            {@link #MODE_CREATE}, {@link #MODE_TRUNCATE},
   *            {@link #MODE_WORLD_READABLE}, and
   *            {@link #MODE_WORLD_WRITEABLE}.
   * @return a new ParcelFileDescriptor pointing to the given file.
   * @throws FileNotFoundException if the given file does not exist or can not
   *             be opened with the requested mode.
   * @see #parseMode(String)
   */
  public static ParcelFileDescriptor open(File file, int mode) throws FileNotFoundException {
      final FileDescriptor fd = openInternal(file, mode);
      if (fd == null) return null;
      return new ParcelFileDescriptor(fd);
  }

 ParcelFileDescriptor mFileDescriptor;
 PdfRenderer mPdfRenderer;  
//根据文件对象创建
mFileDescriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
 // This is the PdfRenderer we use to render the PDF.
 if (mFileDescriptor != null) {
   mPdfRenderer = new PdfRenderer(mFileDescriptor);
 }

private PdfRenderer.Page mCurrentPage;
private void showPage(int index) {
    if (mPdfRenderer.getPageCount() <= index) {
        return;
    }
    // Make sure to close the current page before opening another one.
    if (null != mCurrentPage) {
        mCurrentPage.close();
    }
    // Use `openPage` to open a specific page in PDF.
    mCurrentPage = mPdfRenderer.openPage(index);
    // Important: the destination bitmap must be ARGB (not RGB).
    Bitmap bitmap = Bitmap.createBitmap(mCurrentPage.getWidth(), 			   mCurrentPage.getHeight(),Bitmap.Config.ARGB_8888);
    // Here, we render the page onto the Bitmap.
    // To render a portion of the page, use the second and third parameter. Pass nulls to get
    // the default result.
    // Pass either RENDER_MODE_FOR_DISPLAY or RENDER_MODE_FOR_PRINT for the last parameter.
    mCurrentPage.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
    // We are ready to show the Bitmap to user.
    mImageView.setImageBitmap(bitmap);
    updateUi();
}

public class PdfRendererBasicFragment extends Fragment implements View.OnClickListener {

    /**
     * Key string for saving the state of current page index.
     */
    private static final String STATE_CURRENT_PAGE_INDEX = "current_page_index";

    /**
     * The filename of the PDF.
     */
    private static final String FILENAME = "sample.pdf";

    /**
     * File descriptor of the PDF.
     */
    private ParcelFileDescriptor mFileDescriptor;

    /**
     * {@link android.graphics.pdf.PdfRenderer} to render the PDF.
     */
    private PdfRenderer mPdfRenderer;

    /**
     * Page that is currently shown on the screen.
     */
    private PdfRenderer.Page mCurrentPage;

    /**
     * {@link android.widget.ImageView} that shows a PDF page as a {@link android.graphics.Bitmap}
     */
    private ImageView mImageView;

    /**
     * {@link android.widget.Button} to move to the previous page.
     */
    private Button mButtonPrevious;

    /**
     * {@link android.widget.Button} to move to the next page.
     */
    private Button mButtonNext;

    /**
     * PDF page index
     */
    private int mPageIndex;

    public PdfRendererBasicFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_pdf_renderer_basic, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        // Retain view references.
        mImageView = (ImageView) view.findViewById(R.id.image);
        mButtonPrevious = (Button) view.findViewById(R.id.previous);
        mButtonNext = (Button) view.findViewById(R.id.next);
        // Bind events.
        mButtonPrevious.setOnClickListener(this);
        mButtonNext.setOnClickListener(this);

        mPageIndex = 0;
        // If there is a savedInstanceState (screen orientations, etc.), we restore the page index.
        if (null != savedInstanceState) {
            mPageIndex = savedInstanceState.getInt(STATE_CURRENT_PAGE_INDEX, 0);
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        try {
            openRenderer(getActivity());
            showPage(mPageIndex);
        } catch (IOException e) {
            e.printStackTrace();
            Toast.makeText(getActivity(), "Error! " + e.getMessage(), Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onStop() {
        try {
            closeRenderer();
        } catch (IOException e) {
            e.printStackTrace();
        }
        super.onStop();
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        if (null != mCurrentPage) {
            outState.putInt(STATE_CURRENT_PAGE_INDEX, mCurrentPage.getIndex());
        }
    }

    /**
     * Sets up a {@link android.graphics.pdf.PdfRenderer} and related resources.
     */
    private void openRenderer(Context context) throws IOException {
        // In this sample, we read a PDF from the assets directory.
        File file = new File(context.getCacheDir(), FILENAME);
        if (!file.exists()) {
            // Since PdfRenderer cannot handle the compressed asset file directly, we copy it into
            // the cache directory.
            InputStream asset = context.getAssets().open(FILENAME);
            FileOutputStream output = new FileOutputStream(file);
            final byte[] buffer = new byte[1024];
            int size;
            while ((size = asset.read(buffer)) != -1) {
                output.write(buffer, 0, size);
            }
            asset.close();
            output.close();
        }
        mFileDescriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
        // This is the PdfRenderer we use to render the PDF.
        if (mFileDescriptor != null) {
            mPdfRenderer = new PdfRenderer(mFileDescriptor);
        }
    }

    /**
     * Closes the {@link android.graphics.pdf.PdfRenderer} and related resources.
     *
     * @throws java.io.IOException When the PDF file cannot be closed.
     */
    private void closeRenderer() throws IOException {
        if (null != mCurrentPage) {
            mCurrentPage.close();
        }
        mPdfRenderer.close();
        mFileDescriptor.close();
    }

    /**
     * Shows the specified page of PDF to the screen.
     *
     * @param index The page index.
     */
    private void showPage(int index) {
        if (mPdfRenderer.getPageCount() <= index) {
            return;
        }
        // Make sure to close the current page before opening another one.
        if (null != mCurrentPage) {
            mCurrentPage.close();
        }
        // Use `openPage` to open a specific page in PDF.
        mCurrentPage = mPdfRenderer.openPage(index);
        // Important: the destination bitmap must be ARGB (not RGB).
        Bitmap bitmap = Bitmap.createBitmap(mCurrentPage.getWidth(), mCurrentPage.getHeight(),
                Bitmap.Config.ARGB_8888);
        // Here, we render the page onto the Bitmap.
        // To render a portion of the page, use the second and third parameter. Pass nulls to get
        // the default result.
        // Pass either RENDER_MODE_FOR_DISPLAY or RENDER_MODE_FOR_PRINT for the last parameter.
        mCurrentPage.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
        // We are ready to show the Bitmap to user.
        mImageView.setImageBitmap(bitmap);
        updateUi();
    }

    /**
     * Updates the state of 2 control buttons in response to the current page index.
     */
    private void updateUi() {
        int index = mCurrentPage.getIndex();
        int pageCount = mPdfRenderer.getPageCount();
        mButtonPrevious.setEnabled(0 != index);
        mButtonNext.setEnabled(index + 1 < pageCount);
        getActivity().setTitle(getString(R.string.app_name_with_index, index + 1, pageCount));
    }

    /**
     * Gets the number of pages in the PDF. This method is marked as public for testing.
     *
     * @return The number of pages.
     */
    public int getPageCount() {
        return mPdfRenderer.getPageCount();
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.previous: {
                // Move to the previous page
                showPage(mCurrentPage.getIndex() - 1);
                break;
            }
            case R.id.next: {
                // Move to the next page
                showPage(mCurrentPage.getIndex() + 1);
                break;
            }
        }
    }

}