如何从Android应用程序打开PDF（在单独的PDF查看器应用程序中）

Question

目标是能够将PDF文件添加到应用程序的“资产”文件夹中，并让用户打开该PDF PDF应用程序（ezPDFReader，Adobe Reader等）。这并非完全简单，因为PDF首先需要将资产文件夹复制到设备存储上。如果设备上没有PDF阅读器应用程序，我们需要显示一条警告消息并指示他们到Play商店下载。

Answer 1

这是为我工作的解决方案。这是一个名为PdfHandler的类，下面介绍如何使用它 - 只需将pdf文件放入资源文件夹。如果可用，它将在PDF查看器应用程序中打开它，并且如果不显示警告消息并将用户引导至Adobe Reader Play商店条目。

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

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(); 
      } 
     } 
    } 

Answer 3

发表奥利下的PdfHandler完美的作品，但它是一个有点慢，因为它复制PDF首先从资产存储它才能打开。如果使用ContentProvider，打开PDF将会更快。

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

AndroidManifest.xml中

<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; 
    } 
}