android code to play the video from the sd card

Question

I need android code to display the video listing from the gallery or sdcard and play when click on that.can anybody help.Please. I have run the following code.but it shows the application has stopped unexpectedly

public class StartActivity extends Activity {

/** Called when the activity is first created. */
private final static Uri MEDIA_EXTERNAL_CONTENT_URI = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
private final static String _ID = MediaStore.Video.Media._ID;
private final static String MEDIA_DATA = MediaStore.Video.Media.DATA;
private GridView _gallery;
private Cursor _cursor;
private int _columnIndex;
private int[] _videosId;
private Uri _contentUri;
protected Context _context;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    initVideosId();
    setGalleryAdapter();
}
private void initVideosId() {
    try {
    //Here we set up a string array of the thumbnail ID column we want to get back
     String [] proj={_ID};
      //Now we create the cursor pointing to the external thumbnail store
     _cursor = managedQuery(_contentUri,
     proj, // Which columns to return
     null,       // WHERE clause; which rows to return (all rows)
     null,       // WHERE clause selection arguments (none)
     null); // Order-by clause (ascending by name)
     int count= _cursor.getCount();
     // We now get the column index of the thumbnail id
     _columnIndex = _cursor.getColumnIndex(_ID);
     //initialize
     _videosId = new int[count];
     //move position to first element
     _cursor.moveToFirst(); 
     for(int i=0;i<count;i++)
     { 
     int id = _cursor.getInt(_columnIndex);
     //
     _videosId[i]= id;
     //
     _cursor.moveToNext();
     //
     }
    }
    catch(Exception ex)
    {
    showToast(ex.getMessage().toString()); 
    }
    }
private void setGalleryAdapter() {
    _gallery.setAdapter(new VideoGalleryAdapter(_context));
    _gallery.setOnItemClickListener(_itemClickLis);
    }
private class VideoGalleryAdapter extends BaseAdapter 
{
public VideoGalleryAdapter(Context c)
{
_context = c;
}
public int getCount()
{
return _videosId.length;
}
public Object getItem(int position)
{
return position;
}
public long getItemId(int position)
{
return position;
}
public View getView(int position, View convertView, ViewGroup parent)
{
ImageView imgVw= new ImageView(_context);;
try
{
if(convertView!=null)
{
imgVw= (ImageView) convertView;
}
imgVw.setImageBitmap(getImage(_videosId[position]));
imgVw.setLayoutParams(new GridView.LayoutParams(96, 96));
imgVw.setPadding(8, 8, 8, 8);
}
catch(Exception ex)
{
System.out.println("StartActivity:getView()-135: ex " + ex.getClass() +", "+ ex.getMessage());
}
return imgVw;
}
// Create the thumbnail on the fly
private Bitmap getImage(int id) {
Bitmap thumb = MediaStore.Video.Thumbnails.getThumbnail(
getContentResolver(),
id, MediaStore.Video.Thumbnails.MICRO_KIND, null);
return thumb;
}
}
private OnItemClickListener _itemClickLis = new OnItemClickListener()
{
public void OnItemClick(AdapterView parent, View v, int position, long id)
{
// Now we want to actually get the data location of the file
String [] proj={MEDIA_DATA};
// We request our cursor again
_cursor = managedQuery(_contentUri,
proj, // Which columns to return
null,       // WHERE clause; which rows to return (all rows)
null,       // WHERE clause selection arguments (none)
null); // Order-by clause (ascending by name)
// We want to get the column index for the data uri
int count = _cursor.getCount();
_cursor.moveToFirst();
_columnIndex = _cursor.getColumnIndex(MEDIA_DATA);
// Lets move to the selected item in the cursor
_cursor.moveToPosition(position);
// And here we get the filename
String filename = _cursor.getString(_columnIndex);
//*********** You can do anything when you know the file path 
showToast(filename);
//
}

@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
    // TODO Auto-generated method stub

}
};
protected void showToast(String msg)
{
Toast.makeText(_context, msg, Toast.LENGTH_LONG).show();
}