如何从Android应用程序(在单独的PDF查看器应用程序中)打开PDF

Question

目标是能够将PDF文件添加到应用程序的"资产"文件夹中，并允许用户在PDF应用程序（ezPDFReader、Adobe Reader等）中打开该PDF。这并不完全简单，因为PDF首先需要从资产文件夹复制到设备存储中。如果设备上没有PDF查看器应用程序，我们需要显示一条警告消息，并将其引导到Play Store下载。

Answer 1

这是一个适用于我的解决方案。它是一个名为PdfHandler的类，下面是它的使用方法-只需将pdf文件放在assets文件夹中即可。如果有PDF查看器应用程序，它会在其中打开，如果没有，它会显示警告消息，并将用户引导到Adobe Reader Play Store条目。

PdfHandler pdf = new PdfHandler(this);
pdf.openPdf("document.pdf");

PdfHandler类。您应该将文本资源移动到Android字符串资源中。

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.res.AssetManager;
import android.net.Uri;
import android.util.Log;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
/**
 * Handles the opening of PDF files, using whatever app the user has installed to view PDFs
 * If no PDF app installed, shows a warning and directs them to appropriate Store listing
 */
public class PdfHandler {
    public PdfHandler(Context context) {
        this.context = context;
    }
    public void openPdf(String filename) {
        if (isPdfAppAvailable()) {
            copyPdfAndOpenIt(filename);
        } else {
            showPdfWarning();
        }
    }
    private void copyPdfAndOpenIt(String filename) {
        try {
            File file = copyPdfFromAssetsToStorage(filename);
            startPdfIntent(file);
        } catch (Exception e) {
            Log.e("PdfHandler", "Error handling the PDF file", e);
        }
    }
    private File copyPdfFromAssetsToStorage(String filename) throws Exception {
        String tempFilename = "temp.pdf";
        AssetManager is = context.getAssets();
        InputStream inputStream = is.open(filename);
        String outFilename = context.getFilesDir() + "/" + tempFilename;
        FileOutputStream outputStream = context.openFileOutput(tempFilename, Context.MODE_WORLD_READABLE);
        copy(inputStream, outputStream);
        outputStream.flush();
        outputStream.close();
        inputStream.close();
        return new File(outFilename);
    }
    private void copy(InputStream fis, FileOutputStream fos) throws IOException {
        byte[] b = new byte[8];
        int i;
        while ((i = fis.read(b)) != -1) {
            fos.write(b, 0, i);
        }
    }
    private boolean isPdfAppAvailable() {
        PackageManager packageManager = context.getPackageManager();
        Intent testIntent = new Intent(Intent.ACTION_VIEW);
        testIntent.setType("application/pdf");
        List list = packageManager.queryIntentActivities(testIntent, PackageManager.MATCH_DEFAULT_ONLY);
        return list.size() > 0;
    }
    private void startPdfIntent(File file) {
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_VIEW);
        Uri uri = Uri.fromFile(file);
        intent.setDataAndType(uri, "application/pdf");
        context.startActivity(intent);
    }
    private void showPdfWarning() {
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setMessage("Please install an app to view PDF file");
        builder.setCancelable(false);
        builder.setPositiveButton("Install", getButtonListener());
        builder.setNegativeButton("Cancel", null);
        builder.setTitle("PDF Viewer");
        AlertDialog alert = builder.create();
        alert.show();
    }
    private DialogInterface.OnClickListener getButtonListener() {
        return new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialogInterface, int i) {
                    goToGooglePlayStoreEntry();
                }
            };
    }
    private void goToGooglePlayStoreEntry() {
        context.startActivity(getAppListingIntent());
    }
    private Intent getAppListingIntent() {
        Intent intent = new Intent(Intent.ACTION_VIEW);
        String pdfAppPackageName = "com.adobe.reader";
        intent.setData(Uri.parse("market://details?id=" + pdfAppPackageName));
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        return intent;
    }
    private Context context;
}

Answer 2

Ollie C发布的PdfHandler运行良好，但速度有点慢，因为它在打开PDF之前先将PDF从资产复制到存储中。如果您使用ContentProvider，打开PDF会更快。

请注意，如果您的文件名是MyPdf.pdf，则该文件应为assets/public_pdfs/MyPdf.pdf.mp3。路径public_pdfs仅导出您真正想要导出的pdf，.mp3扩展名用于防止压缩。

AndroidManifest.xml

<provider android:authorities="my.app.PdfContentProvider" android:enabled="true" android:exported="true" android:name="my.app.PdfContentProvider">
</provider>

打开PDF

Intent intent = new Intent();
intent.setAction(Intent.ACTION_VIEW);
Uri uri = Uri.parse("content://my.app.PdfContentProvider/" + filename);
intent.setDataAndType(uri, "application/pdf");
startActivity(intent);

PdfContentProvider.java

public class PdfContentProvider extends ContentProvider
{
  private static final String PDFPATH = "public_pdfs/";
  @Override
  public String getType(Uri uri)
  {
    return "application/pdf";
  }
  @Override
  public AssetFileDescriptor openAssetFile(Uri uri, String mode) throws FileNotFoundException
  {
    AssetManager am = getContext().getAssets();
    String file_name = uri.getLastPathSegment();
    if (file_name == null) throw new FileNotFoundException();
    AssetFileDescriptor afd = null;
    try
    {
      afd = am.openFd(PDFPATH + file_name + ".mp3");
    }
    catch (IOException e)
    {
      e.printStackTrace();
    }
    return afd;
  }
  private final static String[] COLUMNS = {OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE};
  @Override
  /**
   * This function is required for it to work on the Quickoffice at Android 4.4 (KitKat)
   */
  public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
  {
    if (projection == null)
    {
      projection = COLUMNS;
    }
    String[] cols = new String[projection.length];
    Object[] values = new Object[projection.length];
    int i = 0;
    for (String col : projection)
    {
      if (OpenableColumns.DISPLAY_NAME.equals(col))
      {
        cols[i] = OpenableColumns.DISPLAY_NAME;
        values[i++] = uri.getLastPathSegment();
      }
      else if (OpenableColumns.SIZE.equals(col))
      {
        cols[i] = OpenableColumns.SIZE;
        values[i++] = AssetFileDescriptor.UNKNOWN_LENGTH;
      }
    }
    cols = copyOf(cols, i);
    values = copyOf(values, i);
    final MatrixCursor cursor = new MatrixCursor(cols, 1);
    cursor.addRow(values);
    return cursor;
  }
  private static String[] copyOf(String[] original, int newLength)
  {
    final String[] result = new String[newLength];
    System.arraycopy(original, 0, result, 0, newLength);
    return result;
  }
  private static Object[] copyOf(Object[] original, int newLength)
  {
    final Object[] result = new Object[newLength];
    System.arraycopy(original, 0, result, 0, newLength);
    return result;
  }
  @Override
  public boolean onCreate()
  {
    return true;
  }
  @Override
  public Uri insert(Uri uri, ContentValues values)
  {
    return null;
  }
  @Override
  public int delete(Uri uri, String selection, String[] selectionArgs)
  {
    return 0;
  }
  @Override
  public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
  {
    return 0;
  }
}

Answer 3

LoginProgress task = new LoginProgress();
task.execute(Pdffile);


public class LoginProgress extends AsyncTask<Void, Void, Void> {
        private ProgressDialog dialog;
        protected Context applicationContext;
        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            this.dialog.dismiss();
        }
        @Override
        protected void onPreExecute() {
            this.dialog = ProgressDialog.show(applicationContext,
                    "Data Loading", "Loading .....", true);
        }
        @Override
        protected Void doInBackground(Void... params) {
            // video();
            LoadUrl(Pdffile);
            return null;
        }
        private void LoadUrl(File Pdffile) {
            try {
                u r stuff here
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }