使用AndroidPDFViewer将pdf转换为图片并在android studio中显示。

Question

我正在使用这些说明来显示一个pdf文件(最上面的答案)。

Need help to convert a Pdf page into Bitmap in Android Java

我需要将其转换为位图，因为我希望能够添加一个矩形到它。

该活动似乎可以打开，但我只是得到一个空白屏幕上有一个非常暗淡的灰色框，我想pdf应该显示在那里。

谢谢!

以下是我的代码

//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.support.v7.app.ActionBarActivity;
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;




public class imgviewpdf extends ActionBarActivity {

    //Globals:
    private WebView wv;
    private int ViewSize = 0;

    //OnCreate Method:
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_imgviewpdf);
            //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(imgviewpdf.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() + "/myDoc.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());
        }
    }
}

下面是我的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>

Answer 1

这取决于，如果你希望用户不通过文件管理器或任何其他方式访问文件，而不是通过你的应用程序，那么使用分配给你的应用程序的内部存储。

File file = new File(context.getFilesDir(), filename);

如果您希望文件管理器或任何其他应用程序能够访问这些文件，那么您可以使用外部存储。

String filePath = Environment.getExternalStorageDirectory().getPath()+"/file_name.pdf";
File pdfFile = new File(filePath);
if (!pdfFile.getParentFile().exists()) {
     pdfFile.getParentFile().mkdirs();
  }

在写入文件之前，需要检查父目录是否存在。如果它不存在，那么就生成它。然后你就可以在文件上写东西了。

Answer 2

请了解一下google's page about file storage以及内部和外部存储的优势。

您还可以通过设置让用户做出此选择。