Android 在其库中不支持 PDF。有没有办法在 Android 应用程序中呈现 PDF 文件？
【问题讨论】：
标签： java android pdf android-pdf-api
由于 API Level 21 (Lollipop) Android 提供了PdfRenderer class：
// create a new renderer
PdfRenderer renderer = new PdfRenderer(getSeekableFileDescriptor());
// let us just render all pages
final int pageCount = renderer.getPageCount();
for (int i = 0; i < pageCount; i++) {
Page page = renderer.openPage(i);
// say we render for showing on the screen
page.render(mBitmap, null, null, Page.RENDER_MODE_FOR_DISPLAY);
// do stuff with the bitmap
// close the page
page.close();
}
// close the renderer
renderer.close();
有关详细信息，请参阅sample app。
对于较旧的 API，我推荐 Android PdfViewer library，它非常快速且易于使用，根据 Apache License 2.0 获得许可：
pdfView.fromAsset(String)
.pages(0, 2, 1, 3, 3, 3) // all pages are displayed by default
.enableSwipe(true)
.swipeHorizontal(false)
.enableDoubletap(true)
.defaultPage(0)
.onDraw(onDrawListener)
.onLoad(onLoadCompleteListener)
.onPageChange(onPageChangeListener)
.onPageScroll(onPageScrollListener)
.onError(onErrorListener)
.enableAnnotationRendering(false)
.password(null)
.scrollHandle(null)
.load();
【讨论】：
PDFView Library做一个更详细的例子吗？我们应该在pdfName 中输入什么？函数onDraw、onLoad 和onPageChange 监听器是什么样的？感谢您的帮助:)
public class MyPdfViewActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
WebView mWebView=new WebView(MyPdfViewActivity.this);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setPluginsEnabled(true);
mWebView.loadUrl("https://docs.google.com/gview?embedded=true&url="+LinkTo);
setContentView(mWebView);
}
}
【讨论】：
我根据对这篇文章和其他类似帖子的一些答案做出了一种混合方法：
此解决方案检查是否安装了 PDF 阅读器应用程序并执行以下操作： - 如果安装了阅读器，请将 PDF 文件下载到设备并启动 PDF 阅读器应用程序 - 如果没有安装阅读器，询问用户是否想通过 Google Drive 在线查看 PDF 文件
注意！此解决方案使用 API9（Android 2.3 或 Gingerbread）中引入的 Android DownloadManager 类。这意味着它不适用于 Android 2.2 或更早版本。
我写了一篇关于它的博客文章here，但为了完整起见，我在下面提供了完整的代码：
public class PDFTools {
private static final String GOOGLE_DRIVE_PDF_READER_PREFIX = "http://drive.google.com/viewer?url=";
private static final String PDF_MIME_TYPE = "application/pdf";
private static final String HTML_MIME_TYPE = "text/html";
/**
* If a PDF reader is installed, download the PDF file and open it in a reader.
* Otherwise ask the user if he/she wants to view it in the Google Drive online PDF reader.<br />
* <br />
* <b>BEWARE:</b> This method
* @param context
* @param pdfUrl
* @return
*/
public static void showPDFUrl( final Context context, final String pdfUrl ) {
if ( isPDFSupported( context ) ) {
downloadAndOpenPDF(context, pdfUrl);
} else {
askToOpenPDFThroughGoogleDrive( context, pdfUrl );
}
}
/**
* Downloads a PDF with the Android DownloadManager and opens it with an installed PDF reader app.
* @param context
* @param pdfUrl
*/
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
public static void downloadAndOpenPDF(final Context context, final String pdfUrl) {
// Get filename
final String filename = pdfUrl.substring( pdfUrl.lastIndexOf( "/" ) + 1 );
// The place where the downloaded PDF file will be put
final File tempFile = new File( context.getExternalFilesDir( Environment.DIRECTORY_DOWNLOADS ), filename );
if ( tempFile.exists() ) {
// If we have downloaded the file before, just go ahead and show it.
openPDF( context, Uri.fromFile( tempFile ) );
return;
}
// Show progress dialog while downloading
final ProgressDialog progress = ProgressDialog.show( context, context.getString( R.string.pdf_show_local_progress_title ), context.getString( R.string.pdf_show_local_progress_content ), true );
// Create the download request
DownloadManager.Request r = new DownloadManager.Request( Uri.parse( pdfUrl ) );
r.setDestinationInExternalFilesDir( context, Environment.DIRECTORY_DOWNLOADS, filename );
final DownloadManager dm = (DownloadManager) context.getSystemService( Context.DOWNLOAD_SERVICE );
BroadcastReceiver onComplete = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if ( !progress.isShowing() ) {
return;
}
context.unregisterReceiver( this );
progress.dismiss();
long downloadId = intent.getLongExtra( DownloadManager.EXTRA_DOWNLOAD_ID, -1 );
Cursor c = dm.query( new DownloadManager.Query().setFilterById( downloadId ) );
if ( c.moveToFirst() ) {
int status = c.getInt( c.getColumnIndex( DownloadManager.COLUMN_STATUS ) );
if ( status == DownloadManager.STATUS_SUCCESSFUL ) {
openPDF( context, Uri.fromFile( tempFile ) );
}
}
c.close();
}
};
context.registerReceiver( onComplete, new IntentFilter( DownloadManager.ACTION_DOWNLOAD_COMPLETE ) );
// Enqueue the request
dm.enqueue( r );
}
/**
* Show a dialog asking the user if he wants to open the PDF through Google Drive
* @param context
* @param pdfUrl
*/
public static void askToOpenPDFThroughGoogleDrive( final Context context, final String pdfUrl ) {
new AlertDialog.Builder( context )
.setTitle( R.string.pdf_show_online_dialog_title )
.setMessage( R.string.pdf_show_online_dialog_question )
.setNegativeButton( R.string.pdf_show_online_dialog_button_no, null )
.setPositiveButton( R.string.pdf_show_online_dialog_button_yes, new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
openPDFThroughGoogleDrive(context, pdfUrl);
}
})
.show();
}
/**
* Launches a browser to view the PDF through Google Drive
* @param context
* @param pdfUrl
*/
public static void openPDFThroughGoogleDrive(final Context context, final String pdfUrl) {
Intent i = new Intent( Intent.ACTION_VIEW );
i.setDataAndType(Uri.parse(GOOGLE_DRIVE_PDF_READER_PREFIX + pdfUrl ), HTML_MIME_TYPE );
context.startActivity( i );
}
/**
* Open a local PDF file with an installed reader
* @param context
* @param localUri
*/
public static final void openPDF(Context context, Uri localUri ) {
Intent i = new Intent( Intent.ACTION_VIEW );
i.setDataAndType( localUri, PDF_MIME_TYPE );
context.startActivity( i );
}
/**
* Checks if any apps are installed that supports reading of PDF files.
* @param context
* @return
*/
public static boolean isPDFSupported( Context context ) {
Intent i = new Intent( Intent.ACTION_VIEW );
final File tempFile = new File( context.getExternalFilesDir( Environment.DIRECTORY_DOWNLOADS ), "test.pdf" );
i.setDataAndType( Uri.fromFile( tempFile ), PDF_MIME_TYPE );
return context.getPackageManager().queryIntentActivities( i, PackageManager.MATCH_DEFAULT_ONLY ).size() > 0;
}
}
【讨论】：
你可以通过 import 使用一个简单的方法
implementation 'com.github.barteksc:android-pdf-viewer:2.8.2'
XML 代码是
<com.github.barteksc.pdfviewer.PDFView
android:id="@+id/pdfv"
android:layout_width="match_parent"
android:layout_height="match_parent">
</com.github.barteksc.pdfviewer.PDFView>
只需声明一个文件并将其添加到资产文件夹并指定名称
PDFView pdfView=findViewById(R.id.pdfv);
pdfView.fromAsset("agl.pdf").load();
【讨论】：
PdfiumAndroid，它本身已经是 18.4MB
agl.pdf 文件应该存在于assets 文件夹中
在此处下载源代码 (Display PDF file inside my android application)
在您的成绩中添加此依赖项：
编译com.github.barteksc:android-pdf-viewer:2.0.3
activity_main.xml
<RelativeLayout android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff"
xmlns:android="http://schemas.android.com/apk/res/android" >
<TextView
android:layout_width="match_parent"
android:layout_height="40dp"
android:background="@color/colorPrimaryDark"
android:text="View PDF"
android:textColor="#ffffff"
android:id="@+id/tv_header"
android:textSize="18dp"
android:gravity="center"></TextView>
<com.github.barteksc.pdfviewer.PDFView
android:id="@+id/pdfView"
android:layout_below="@+id/tv_header"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
MainActivity.java
import android.app.Activity;
import android.database.Cursor;
import android.net.Uri;
import android.provider.OpenableColumns;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import com.github.barteksc.pdfviewer.PDFView;
import com.github.barteksc.pdfviewer.listener.OnLoadCompleteListener;
import com.github.barteksc.pdfviewer.listener.OnPageChangeListener;
import com.github.barteksc.pdfviewer.scroll.DefaultScrollHandle;
import com.shockwave.pdfium.PdfDocument;
import java.util.List;
public class MainActivity extends Activity implements OnPageChangeListener,OnLoadCompleteListener{
private static final String TAG = MainActivity.class.getSimpleName();
public static final String SAMPLE_FILE = "android_tutorial.pdf";
PDFView pdfView;
Integer pageNumber = 0;
String pdfFileName;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pdfView= (PDFView)findViewById(R.id.pdfView);
displayFromAsset(SAMPLE_FILE);
}
private void displayFromAsset(String assetFileName) {
pdfFileName = assetFileName;
pdfView.fromAsset(SAMPLE_FILE)
.defaultPage(pageNumber)
.enableSwipe(true)
.swipeHorizontal(false)
.onPageChange(this)
.enableAnnotationRendering(true)
.onLoad(this)
.scrollHandle(new DefaultScrollHandle(this))
.load();
}
@Override
public void onPageChanged(int page, int pageCount) {
pageNumber = page;
setTitle(String.format("%s %s / %s", pdfFileName, page + 1, pageCount));
}
@Override
public void loadComplete(int nbPages) {
PdfDocument.Meta meta = pdfView.getDocumentMeta();
printBookmarksTree(pdfView.getTableOfContents(), "-");
}
public void printBookmarksTree(List<PdfDocument.Bookmark> tree, String sep) {
for (PdfDocument.Bookmark b : tree) {
Log.e(TAG, String.format("%s %s, p %d", sep, b.getTitle(), b.getPageIdx()));
if (b.hasChildren()) {
printBookmarksTree(b.getChildren(), sep + "-");
}
}
}
}
【讨论】：
assetFileName pdf 文件应该存在于assets 文件夹中
我终于能够修改butelo's code 以使用pdf.js 打开Android 文件系统中的任何PDF 文件。代码可以找到on my GitHub
我所做的是将pdffile.js 修改为读取HTML 参数file，如下所示：
var url = getURLParameter('file');
function getURLParameter(name) {
return decodeURIComponent((new RegExp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec(location.search)||[,""])[1].replace(/\+/g, '%20'))||null}
所以你需要做的只是在index.html 之后附加文件路径，如下所示：
Uri path = Uri.parse(Environment.getExternalStorageDirectory().toString() + "/data/test.pdf");
webView.loadUrl("file:///android_asset/pdfviewer/index.html?file=" + path);
更新 path 变量以指向 Adroid 文件系统中的有效 PDF。
【讨论】：
为了增加一点亮点，我将不得不使用 Mozilla 的 pdf.js 解决方案。这是一个已经写得很好的实现的链接：https://bitbucket.org/butelo/pdfviewer/。
以下是我在 Android Activity 中添加的编辑：
private String getInternalPDFURL(String interalPDFName){
return "file:///android_asset/pdfviewer/index.html?pdf=" + interalPDFName + ".pdf";
}
这是我在pdffile.js中所做的修改：
var url = '../' + getPDFURL();
function getPDFURL(){
var query = window.location.search.substring(1);
var vars = query.split("=");
var pdfPage = vars[1];
return pdfPage;
}
【讨论】：
我使用以下代码通过 Wi-Fi 打开和打印 PDF。我正在发送我的整个代码，希望对您有所帮助。
public class MainActivity extends Activity {
int Result_code = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button mButton = (Button)findViewById(R.id.button1);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
PrintManager printManager = (PrintManager)getSystemService(Context.PRINT_SERVICE);
String jobName = " Document";
printManager.print(jobName, pda, null);
}
});
}
public void openDocument(String name) {
Intent intent = new Intent(android.content.Intent.ACTION_VIEW);
File file = new File(name);
String extension = android.webkit.MimeTypeMap.getFileExtensionFromUrl(Uri.fromFile(file).toString());
String mimetype = android.webkit.MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
if (extension.equalsIgnoreCase("") || mimetype == null) {
// if there is no extension or there is no definite mimetype, still try to open the file
intent.setDataAndType(Uri.fromFile(file), "text/*");
}
else {
intent.setDataAndType(Uri.fromFile(file), mimetype);
}
// custom message for the intent
startActivityForResult((Intent.createChooser(intent, "Choose an Application:")), Result_code);
//startActivityForResult(intent, Result_code);
//Toast.makeText(getApplicationContext(),"There are no email clients installed.", Toast.LENGTH_SHORT).show();
}
@SuppressLint("NewApi")
PrintDocumentAdapter pda = new PrintDocumentAdapter(){
@Override
public void onWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback){
InputStream input = null;
OutputStream output = null;
try {
String filename = Environment.getExternalStorageDirectory() + "/" + "Holiday.pdf";
File file = new File(filename);
input = new FileInputStream(file);
output = new FileOutputStream(destination.getFileDescriptor());
byte[] buf = new byte[1024];
int bytesRead;
while ((bytesRead = input.read(buf)) > 0) {
output.write(buf, 0, bytesRead);
}
callback.onWriteFinished(new PageRange[]{PageRange.ALL_PAGES});
}
catch (FileNotFoundException ee){
//Catch exception
}
catch (Exception e) {
//Catch exception
}
finally {
try {
input.close();
output.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
public void onLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras){
if (cancellationSignal.isCanceled()) {
callback.onLayoutCancelled();
return;
}
// int pages = computePageCount(newAttributes);
PrintDocumentInfo pdi = new PrintDocumentInfo.Builder("Name of file").setContentType(PrintDocumentInfo.CONTENT_TYPE_DOCUMENT).build();
callback.onLayoutFinished(pdi, true);
}
};
}
【讨论】：
Android webview 中无论如何都无法预览 pdf 文档。如果你想预览 base64 pdf。需要第三方库。
构建.Gradle
compile 'com.github.barteksc:android-pdf-viewer:2.7.0'
dialog_pdf_viewer
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_horizontal"
android:orientation="vertical">
<ImageView
android:id="@+id/dialog_pdf_viewer_close"
style="@style/ExitButtonImageViewStyle"
android:src="@drawable/popup_exit" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:background="@color/white"
android:orientation="vertical">
<com.github.barteksc.pdfviewer.PDFView
android:id="@+id/pdfView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<View style="@style/HorizontalLine" />
<com.pozitron.commons.customviews.ButtonFont
android:id="@+id/dialog_pdf_viewer_button"
style="@style/ButtonPrimary2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="@string/agreed" />
</LinearLayout>
DailogPDFViewer.java
public class DialogPdfViewer extends Dialog {
PDFView pdfView;
byte[] decodedString;
public interface OnDialogPdfViewerListener {
void onAgreeClick(DialogPdfViewer dialogFullEula);
void onCloseClick(DialogPdfViewer dialogFullEula);
}
public DialogPdfViewer(Context context, String base64, final DialogPdfViewer.OnDialogPdfViewerListener onDialogPdfViewerListener) {
super(context);
setContentView(R.layout.dialog_pdf_viewer);
findViewById(R.id.dialog_pdf_viewer_close).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onDialogPdfViewerListener.onCloseClick(DialogPdfViewer.this);
}
});
findViewById(R.id.dialog_pdf_viewer_button).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onDialogPdfViewerListener.onAgreeClick(DialogPdfViewer.this);
}
});
decodedString = Base64.decode(base64.toString(), Base64.DEFAULT);
pdfView = ((PDFView) findViewById(R.id.pdfView));
pdfView.fromBytes(decodedString).load();
setOnKeyListener(new OnKeyListener() {
@Override
public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
onDialogPdfViewerListener.onCloseClick(DialogPdfViewer.this);
}
return true;
}
});
}
}
【讨论】：
最好的方法是使用 android lollipop 及更高版本提供的 PDF Render 类 它会比其他用原生 SDK 编写的库更轻量级
【讨论】：
以下是如何在不使用任何第三方库的情况下从 PDF 文件中获取 Bitmap 的缩略图。
private fun loadThumbnailFromPdfFile(file:File, thumbnailImageView: ImageView) {
Log.d(TAG, "loadThumbnailFromPdfFile: ")
val mFileDescriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY)
// This is the PdfRenderer we use to render the PDF.
val mPdfRenderer = PdfRenderer(mFileDescriptor)
//check if pdf have no pages then we can't show pdf thumbnail
if (mPdfRenderer.pageCount <= 0) {
//No pages in pdf, can't show thumbnail
Log.d(TAG, "loadThumbnailFromPdfFile: No pages in pdf")
} else {
//There are page(s) in pdf, can show pdf thumbnail
//Use `openPage` to open a specific page in PDF.
val mCurrentPage = mPdfRenderer.openPage(0)
// Important: the destination bitmap must be ARGB (not RGB).
val bitmap = Bitmap.createBitmap(mCurrentPage.width, mCurrentPage.height, 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.
thumbnailImageView.setImageBitmap(bitmap)
}
}
【讨论】：
我在使用 GoogleDrive 选项时遇到了问题，有时它会无法加载文档和“com.github.barteksc:android-pdf-viewer:2.7.0”，尽管它的文档使加载文档看起来很容易从一个链接，我没有让它工作。它总是抛出 FileNotFoundException，所以经过进一步研究，我了解到它会下载 pdf，所以你必须让它指向那个文档，我觉得这有点乏味。
您可以在此处尝试使用此库。它非常易于使用并且至今仍在维护，我不知道几年后他们是否会停止更新它。它会缓存文档，您甚至不需要跟踪它的路径。
https://levelup.gitconnected.com/open-pdf-files-in-android-without-webviews-or-intents-3cc960752cca
【讨论】：