问如何在我的android应用程序中读取pdf？

EN

@Override
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    File images = Environment.getExternalStorageDirectory();
    imagelist = images.listFiles(new FilenameFilter()
    {  
            public boolean accept(File dir, String name)  
            {  
                    return ((name.endsWith(".pdf")));
            }  
    }); 
    pdflist = new String[imagelist.length]; 
    for(int i = 0;i<imagelist.length;i++)
    {
            pdflist[i] = imagelist[i].getName();
    }
    this.setListAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, pdflist));
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) 
{
        super.onListItemClick(l, v, position, id);
        String path = imagelist[(int)id].getAbsolutePath();
        openPdfIntent(path);
}

private void openPdfIntent(String path) 
{
    try
    {
      final Intent intent = new Intent(First.this, Second.class);
      intent.putExtra(PdfViewerActivity.EXTRA_PDFFILENAME, path);
      startActivity(intent);
    }
    catch (Exception e) 
    {
      e.printStackTrace();
    }
}

public class Second extends PdfViewerActivity 
{

@Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
}

public int getPreviousPageImageResource() {
    return R.drawable.left_arrow;
}

public int getNextPageImageResource() {
    return R.drawable.right_arrow;
}

public int getZoomInImageResource() {
    return R.drawable.zoom_in;
}

public int getZoomOutImageResource() {
    return R.drawable.zoom_out;
}

public int getPdfPasswordLayoutResource() {
    return R.layout.pdf_file_password;
}

public int getPdfPageNumberResource() {
    return R.layout.dialog_pagenumber;
}

public int getPdfPasswordEditField() {
    return R.id.etPassword;
}

public int getPdfPasswordOkButton() {
    return R.id.btOK;
}

public int getPdfPasswordExitButton() {
    return R.id.btExit;
}

public int getPdfPageNumberEditField() {
    return R.id.pagenum_edit;
}
}

public class OpenPdf extends Activity { 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 

        Button button = (Button) findViewById(R.id.OpenPdfButton); 
        button.setOnClickListener(new View.OnClickListener() { 
            @Override 
            public void onClick(View v) { 
                File file = new File("/sdcard/example.pdf"); 

                if (file.exists()) { 
                    Uri path = Uri.fromFile(file); 
                    Intent intent = new Intent(Intent.ACTION_VIEW); 
                    intent.setDataAndType(path, "application/pdf"); 
                    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 

                    try { 
                        startActivity(intent); 
                    }  
                    catch (ActivityNotFoundException e) { 
                        Toast.makeText(OpenPdf.this,  
                            "No Application Available to View PDF",  
                            Toast.LENGTH_SHORT).show(); 
                    } 
                } 
            } 
        }); 
    } 
}