android - Android Pdf 查看器活动

Question

我是一名 android 初学者，我正在构建一个 PDF 查看器应用程序，我在此链接 Android-Code to Implement PDF Viewer中找到了此代码

尽管我已将 mpbile pdf.jar 添加到我的 java 构建路径中，但 PdfViewerActivity 仍然存在问题！

我真的需要帮助！

Answer 1

首先，要在 android 中查看 pdf，您必须将 pdf 转换为图像，然后将它们显示给用户。（我将使用网络视图）

所以要做到这一点，我们需要这个库。这是我编辑的这个git版本。

将库导入项目后，您需要创建活动。

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>

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
}

加载图像：

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());
    }
}