我正在尝试使用 PdfRenderer，并且要求具有缩放和滚动功能，但在 Android 中 PdfRenderer 不提供对缩放和滚动的任何支持，只有页面导航支持可用。
但我想缩放和滚动支持可以实现，因为 PdfRenderer 使用位图使用 imageview 显示内容。
如何使用 Google PdfRenderer 示例实现缩放和滚动支持？
PS：我正在使用谷歌提供的这个 PdfRenderer 示例，https://github.com/googlesamples/android-PdfRendererBasic
我使用了@yan-yankelevich 的想法，并用 Java 编写了代码。很多问题在于找到适当的缩放和相应的位图大小值。不要忘记 PdfRenderer 仅适用于 API 21+。
带有 PDF 位图的片段fragment_pdf_renderer.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:orientation="vertical"
tools:context=".PdfRendererFragment">
<ScrollView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
<HorizontalScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="@+id/image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@android:color/white"
android:contentDescription="@null" />
</HorizontalScrollView>
</ScrollView>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/from_divider_gray"
android:gravity="center_vertical"
android:orientation="horizontal">
<Button
android:id="@+id/previous"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/previous_page"
android:textSize="13sp" />
<Button
android:id="@+id/next"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/next_page"
android:textSize="13sp" />
<ImageButton
android:id="@+id/zoomout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="0dp"
android:padding="8dp"
android:src="@drawable/ic_zoom_out_black_36dp" />
<ImageButton
android:id="@+id/zoomin"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="0dp"
android:padding="8dp"
android:src="@drawable/ic_zoom_in_black_36dp" />
</LinearLayout>
</LinearLayout>
PdfRendererFragment: _
/**
* This fragment has a big {@ImageView} that shows PDF pages, and 2
* {@link android.widget.Button}s to move between pages. We use a
* {@link android.graphics.pdf.PdfRenderer} to render PDF pages as
* {@link android.graphics.Bitmap}s.
*/
@RequiresApi(Build.VERSION_CODES.LOLLIPOP)
public class PdfRendererFragment 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.
*/
public String FILENAME;
public String PURCHASE_ID;
public int TICKETS_NUMBER;
/**
* 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;
private ImageView mButtonZoomin;
private ImageView mButtonZoomout;
private Button mButtonNext;
private float currentZoomLevel = 12;
/**
* PDF page index
*/
private int mPageIndex;
public PdfRendererFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_pdf_renderer, 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);
mButtonZoomin = view.findViewById(R.id.zoomin);
mButtonZoomout = view.findViewById(R.id.zoomout);
// Bind events.
mButtonPrevious.setOnClickListener(this);
mButtonNext.setOnClickListener(this);
mButtonZoomin.setOnClickListener(this);
mButtonZoomout.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 onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
FILENAME = getActivity().getIntent().getExtras().getString("pdfFilename");
TICKETS_NUMBER = getActivity().getIntent().getExtras().getInt("tickets_number");
PURCHASE_ID = getActivity().getIntent().getExtras().getString("purchaseGuid");
}
@Override
public void onStart() {
super.onStart();
try {
openRenderer(getActivity());
showPage(mPageIndex);
} catch (IOException e) {
e.printStackTrace();
Toast.makeText(getActivity(), getString(R.string.ticket_file_not_found, FILENAME), Toast.LENGTH_SHORT).show();
App app = (App) getActivity().getApplicationContext();
TicketUtil.downloadTicket(app, PURCHASE_ID);
getActivity().finish();
}
}
@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 = TicketUtil.getTicketFile(context, PURCHASE_ID);
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();
mCurrentPage = null;
}
if (null != mPdfRenderer) {
mPdfRenderer.close();
}
if (null != mFileDescriptor) {
mFileDescriptor.close();
}
}
/**
* Zoom level for zoom matrix depends on screen density (dpiAdjustedZoomLevel), but width and height of bitmap depends only on pixel size and don't depend on DPI
* 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).
int newWidth = (int) (getResources().getDisplayMetrics().widthPixels * mCurrentPage.getWidth() / 72 * currentZoomLevel / 40);
int newHeight = (int) (getResources().getDisplayMetrics().heightPixels * mCurrentPage.getHeight() / 72 * currentZoomLevel / 64);
Bitmap bitmap = Bitmap.createBitmap(
newWidth,
newHeight,
Bitmap.Config.ARGB_8888);
Matrix matrix = new Matrix();
float dpiAdjustedZoomLevel = currentZoomLevel * DisplayMetrics.DENSITY_MEDIUM / getResources().getDisplayMetrics().densityDpi;
matrix.setScale(dpiAdjustedZoomLevel, dpiAdjustedZoomLevel);
// Toast.makeText(getActivity(), "width " + String.valueOf(newWidth) + " widthPixels " + getResources().getDisplayMetrics().widthPixels, Toast.LENGTH_LONG).show();
// matrix.postTranslate(-rect.left/mCurrentPage.getWidth(), -rect.top/mCurrentPage.getHeight());
// 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, matrix, 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();
if (pageCount == 1) {
mButtonPrevious.setVisibility(View.GONE);
mButtonNext.setVisibility(View.GONE);
} else {
mButtonPrevious.setEnabled(0 != index);
mButtonNext.setEnabled(index + 1 < pageCount);
}
if (currentZoomLevel == 2) {
mButtonZoomout.setActivated(false);
} else {
mButtonZoomout.setActivated(true);
}
}
/**
* 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
currentZoomLevel = 12;
showPage(mCurrentPage.getIndex() - 1);
break;
}
case R.id.next: {
// Move to the next page
currentZoomLevel = 12;
showPage(mCurrentPage.getIndex() + 1);
break;
}
case R.id.zoomout: {
// Move to the next page
--currentZoomLevel;
showPage(mCurrentPage.getIndex());
break;
}
case R.id.zoomin: {
// Move to the next page
++currentZoomLevel;
showPage(mCurrentPage.getIndex());
break;
}
}
}
}
请注意缩放级别取决于您的屏幕密度，但位图的宽度和高度（以像素为单位）仅取决于您的缩放级别。此外，您需要调整您的尺寸，以便在默认缩放时（对我来说，它是 pdf 全屏呈现，值为 12），您的 PDF 位图不会超过视图中所需的值。
int newWidth = (int) (getResources().getDisplayMetrics().widthPixels * mCurrentPage.getWidth() / 72 * currentZoomLevel / 40);
int newHeight = (int) (getResources().getDisplayMetrics().heightPixels * mCurrentPage.getHeight() / 72 * currentZoomLevel / 64);
Bitmap bitmap = Bitmap.createBitmap(
newWidth,
newHeight,
Bitmap.Config.ARGB_8888);
mCurrentPage.getWidth()返回以 Postscript 点为单位的宽度，其中每个点pt为 1/72 英寸。PS。如果您需要 在android中同时垂直和水平滚动Scrollview垂直和水平
我遇到这种情况时使用的解决方案是：
在 ImageView 中加载 pdfRenderer 页面
将我的 ImageView 放在 ScrollView 中（tadam 滚动管理），并将此 ScrollView 放在 FrameLayout 中
添加两个按钮（在滚动视图之外）来管理放大和缩小（每个按钮都会在我的 ImageView 上触发缩放动画）。您也可以使用手势检测器来管理它，但是这样做时我很难处理滚动行为
添加两个按钮来管理页面更改（仍然在 ScrollView 之外）
希望我有所帮助，如果您需要更详细的信息，请告诉我，但您现在应该知道从哪里开始
这是一个代码示例（不包括页面导航等，但仅包括缩放行为和滚动，其余部分在您链接的 google 代码示例中）代码：C#（但很容易转换为 Java）
private Button _zoomInButton;
private Button _zoomOutButton;
private ImageView _pdfViewContainer;
private float _currentZoomLevel;
private float _zoomFactor;
private float _maxZoomLevel;
private float _minZoomLevel;
private void Init(View view) // the content of this method must go in your OnViewCreated method, here the view being the frameLayout you will find in xml
{
_zoomInButton = view.FindViewById<Button>(Resource.Id.PdfZoomInButton);
_zoomOutButton = view.FindViewById<Button>(Resource.Id.PdfZoomOutButton);
_pdfViewContainer = view.FindViewById<ImageView>(Resource.Id.PdfViewContainer);
_zoomInButton.Click += delegate { ZoomIn(); }; //for you (in Java) this must looks like setOnClickListener(this); and in the onClick metghod you just have to add a case for R.id.PdfZoomInButton containing a call to ZoomIn();
_zoomOutButton.Click += delegate { ZoomOut(); };
_minZoomLevel = 0.9f;
_maxZoomLevel = 1.2f;
_zoomFactor = 0.1f;
}
private void ZoomIn()
{
if (_currentZoomLevel + _zoomFactor < _maxZoomLevel)
{
ScaleAnimation scale = new ScaleAnimation(_currentZoomLevel, _currentZoomLevel + _zoomFactor, _currentZoomLevel, _currentZoomLevel + _zoomFactor, Dimension.RelativeToSelf, 0.5f, Dimension.RelativeToSelf, 0.5f);
scale.Duration = 50;
scale.FillAfter = true;
_pdfViewContainer.StartAnimation(scale);
_currentZoomLevel += _zoomFactor;
}
}
private void ZoomOut()
{
if (_currentZoomLevel - _zoomFactor > _minZoomLevel)
{
ScaleAnimation scale = new ScaleAnimation(_currentZoomLevel, _currentZoomLevel - _zoomFactor, _currentZoomLevel, _currentZoomLevel - _zoomFactor, Dimension.RelativeToSelf, 0.5f, Dimension.RelativeToSelf, 0.5f);
scale.Duration = 50;
scale.FillAfter = true;
_pdfViewContainer.StartAnimation(scale);
_currentZoomLevel -= _zoomFactor;
}
}
XML
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/PdfContainer">
<ScrollView xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scrollbarAlwaysDrawVerticalTrack="true"
android:id="@+id/PdfScrollView">
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="fitCenter"
android:adjustViewBounds="true"
android:scrollbars="vertical"
android:src="@drawable/mediaIconPDF"
android:id="@+id/PdfViewContainer" />
</ScrollView>
<LinearLayout
android:id="@+id/PdfRightLayout"
android:layout_gravity="right"
android:orientation="vertical"
android:gravity="center"
android:layout_width="50dp"
android:layout_height="match_parent"
android:weightSum="1">
<Button
android:id="@+id/PdfZoomInButton"
android:layout_width="match_parent"
android:layout_height="50dp"
android:text="+" />
<space
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.2" />
<Button
android:id="@+id/PdfZoomOutButton"
android:layout_width="match_parent"
android:layout_height="50dp"
android:text="-" />
</LinearLayout>
<LinearLayout
android:id="@+id/PdfBottomLayout"
android:layout_gravity="bottom"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="50dp"
android:background="@color/vogofTransparentGrey"
android:weightSum="1">
<Button
android:id="@+id/PdfPreviousPage"
android:layout_width="0dp"
android:layout_weight="0.15"
android:layout_height="match_parent"
android:text="Prev" />
<TextView
android:id="@+id/PdfCurrentPageLabel"
android:layout_width="0dp"
android:layout_weight="0.7"
android:gravity="center"
android:layout_height="match_parent"
/>
<Button
android:id="@+id/PdfNextPage"
android:layout_width="0dp"
android:layout_weight="0.15"
android:layout_height="match_parent"
android:text="Next" />
</LinearLayout>
</FrameLayout>
有了这个，一些时间来理解它，你应该能够得到想要的结果。祝你今天过得愉快
我在这里找到了更好的答案：CommonsWare 链接的页面上的 PdfRendering 缩放： https ://github.com/commonsguy/cw-omnibus/tree/v8.8/PDF/PdfRenderer 。所以根据 soshial 的回答，你有捏缩放，可以摆脱缩放按钮和常量：
import com.davemorrissey.labs.subscaleview.ImageSource;
import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView;
……
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);
if(mBitmap==null) {
// Important: the destination bitmap must be ARGB (not RGB).
int newWidth = (int) (getResources().getDisplayMetrics().densityDpi * mCurrentPage.getWidth() / 72);
int newHeight = (int) (getResources().getDisplayMetrics().densityDpi * mCurrentPage.getHeight() / 72);
mBitmap = Bitmap.createBitmap(
newWidth,
newHeight,
Bitmap.Config.ARGB_8888);
}
mBitmap.eraseColor(0xFFFFFFFF);
mCurrentPage.render(mBitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
// We are ready to show the Bitmap to user.
mSubsamplingImageView.resetScaleAndCenter();
mSubsamplingImageView.setImage(ImageSource.cachedBitmap(mBitmap));
updateUi();
}
我还添加了位图回收：
/**
* 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();
mCurrentPage = null;
}
if (null != mPdfRenderer) {
mPdfRenderer.close();
}
if (null != mFileDescriptor) {
mFileDescriptor.close();
}
if(mBitmap!=null)
{
mBitmap.recycle();
mBitmap = null;
}
}
而在 xml 中，而不是 ImageView：
<com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
android:id="@+id/report_viewer_image"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
从这个解决方案开始：https ://stackoverflow.com/a/46002017/5049286我找到了一个避免初始缩放系数和其他固定系数的好方法，只改变了这个方法：
private void showPage(int index) {
if (mPdfRenderer.getPageCount() <= index) {
return;
}
if (null != mCurrentPage) {
mCurrentPage.close();
}
mCurrentPage = mPdfRenderer.openPage(index);
int newWidth = (int) (mVerticalScrollView.getWidth() *
currentZoomLevel);
int newHeight = (int) (newWidth *
((float)mCurrentPage.getHeight()/(float)mCurrentPage.getWidth()));
Bitmap bitmap = Bitmap.createBitmap(
newWidth,
newHeight,
Bitmap.Config.ARGB_8888);
mCurrentPage.render(bitmap, null, null,
PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);
mImageView.setImageBitmap(bitmap);
updateUi();
}
使用此解决方案 currentZoomLevel 从 1.0f 开始到 xxx （您决定一个限制）并且缩放 1.0f 的渲染图像适合滚动视图并保持比例......