问题
I know this question has been asked many times but it's still unclear for me if there is an existing and properly working library to natively display PDF documents.
I only want to view a PDF document which is stored inside my app. Opening a new Activity is ok for me, I don't need to display it inside an existing view. I've already built a piece of code to launch an activity intent for reading my local PDF file, but of course, if no PDF Viewer app is already installed on the device, then nothing happens.
I've heard about APV, VuDroid, droidreader, etc but it seems that they all are APKs, not libraries that can be used inside my app code.
So, is there any real Android library to achieve this?
Thanks in advance.
回答1:
This one you can try it which works in offline mode https://github.com/bitfield66/PdfViewerAndroid_Offline
which just accepts pdf path.
回答2:
Firstly to view a pdf in android you have to convert the pdf into images then display them to the user. (i am going to use a webview)
So to do this we need this library. It is my edited version of this git.
After you have imported the library into your project you need to create your activity.
The XML:
<?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">
<WebView
android:id="@+id/webView1"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
The java onCreate:
//Imports:
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Base64;
import android.util.Log;
import android.view.View;
import android.view.ViewTreeObserver;
import android.webkit.WebView;
import com.sun.pdfview.PDFFile;
import com.sun.pdfview.PDFImage;
import com.sun.pdfview.PDFPage;
import com.sun.pdfview.PDFPaint;
import net.sf.andpdf.nio.ByteBuffer;
import net.sf.andpdf.refs.HardReference;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
//Globals:
private WebView wv;
private int ViewSize = 0;
//OnCreate Method:
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Settings
PDFImage.sShowImages = true; // show images
PDFPaint.s_doAntiAlias = true; // make text smooth
HardReference.sKeepCaches = true; // save images in cache
//Setup webview
wv = (WebView)findViewById(R.id.webView1);
wv.getSettings().setBuiltInZoomControls(true);//show zoom buttons
wv.getSettings().setSupportZoom(true);//allow zoom
//get the width of the webview
wv.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener()
{
@Override
public void onGlobalLayout()
{
ViewSize = wv.getWidth();
wv.getViewTreeObserver().removeGlobalOnLayoutListener(this);
}
});
pdfLoadImages();//load images
}
Load Images:
private void pdfLoadImages()
{
try
{
// run async
new AsyncTask<Void, Void, Void>()
{
// create and show a progress dialog
ProgressDialog progressDialog = ProgressDialog.show(MainActivity.this, "", "Opening...");
@Override
protected void onPostExecute(Void result)
{
//after async close progress dialog
progressDialog.dismiss();
}
@Override
protected Void doInBackground(Void... params)
{
try
{
// select a document and get bytes
File file = new File(Environment.getExternalStorageDirectory().getPath()+"/randompdf.pdf");
RandomAccessFile raf = new RandomAccessFile(file, "r");
FileChannel channel = raf.getChannel();
ByteBuffer bb = ByteBuffer.NEW(channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size()));
raf.close();
// create a pdf doc
PDFFile pdf = new PDFFile(bb);
//Get the first page from the pdf doc
PDFPage PDFpage = pdf.getPage(1, true);
//create a scaling value according to the WebView Width
final float scale = ViewSize / PDFpage.getWidth() * 0.95f;
//convert the page into a bitmap with a scaling value
Bitmap page = PDFpage.getImage((int)(PDFpage.getWidth() * scale), (int)(PDFpage.getHeight() * scale), null, true, true);
//save the bitmap to a byte array
ByteArrayOutputStream stream = new ByteArrayOutputStream();
page.compress(Bitmap.CompressFormat.PNG, 100, stream);
stream.close();
byte[] byteArray = stream.toByteArray();
//convert the byte array to a base64 string
String base64 = Base64.encodeToString(byteArray, Base64.DEFAULT);
//create the html + add the first image to the html
String html = "<!DOCTYPE html><html><body bgcolor=\"#7f7f7f\"><img src=\"data:image/png;base64,"+base64+"\" hspace=10 vspace=10><br>";
//loop through the rest of the pages and repeat the above
for(int i = 2; i <= pdf.getNumPages(); i++)
{
PDFpage = pdf.getPage(i, true);
page = PDFpage.getImage((int)(PDFpage.getWidth() * scale), (int)(PDFpage.getHeight() * scale), null, true, true);
stream = new ByteArrayOutputStream();
page.compress(Bitmap.CompressFormat.PNG, 100, stream);
stream.close();
byteArray = stream.toByteArray();
base64 = Base64.encodeToString(byteArray, Base64.DEFAULT);
html += "<img src=\"data:image/png;base64,"+base64+"\" hspace=10 vspace=10><br>";
}
html += "</body></html>";
//load the html in the webview
wv.loadDataWithBaseURL("", html, "text/html","UTF-8", "");
}
catch (Exception e)
{
Log.d("CounterA", e.toString());
}
return null;
}
}.execute();
System.gc();// run GC
}
catch (Exception e)
{
Log.d("error", e.toString());
}
}
回答3:
I like the MuPDF Adnroid lib since it written in C++/NDK and it has unique features like clickable images (I mean an URL linked to the image) - met no other lib with this feature and I was really need it.
You actually can open PDF using no lib at all: using WebView via google docs but I don't like this way due to IC is required all the time while using MuPDF I can DL pdf file and freely open it offline any time. Also WebView way is more "hard" for device meaning battery draining + lags + CPU heating and it uses more trafic (if compared to DL&show way).
来源：https://stackoverflow.com/questions/11243178/android-pdf-viewer-library