怎么在电话记忆卡里创建文件夹然后保存图像？

Question

怎么在电话的记忆卡创建新的文件夹"MyFolder"然后将所有拍的照片保存到那个文件夹中？请帮下我。
下边的代码都会将所有的照片都保存到收集默认图片库中。我想要创建一个新的文件夹然后把所有拍的照片都保存到那个文件夹中，我应该怎么做？

public class PhotoCaptureExample extends Activity 
  {
protected Button _button;
protected ImageView _image;
protected TextView _field;
protected String _path;
protected boolean _taken;

protected static final String PHOTO_TAKEN   = "photo_taken";

 @Override
  public void onCreate(Bundle savedInstanceState) 
 {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);

    _image = ( ImageView ) findViewById( R.id.image );
    _field = ( TextView ) findViewById( R.id.field );
    _button = ( Button ) findViewById( R.id.button );
    _button.setOnClickListener( new ButtonClickHandler() );
   ;
  _path = Environment.getExternalStorageDirectory() + "/myfolder   
 /"+System.currentTimeMillis()+".jpg";




    File dir = new File(_path );
    try{
      if(dir.mkdir()) {
         System.out.println("Directory created");
      } 
      else {
         System.out.println("Directory is not created");
      }}
      catch(Exception e){

    }   
}

public class ButtonClickHandler implements View.OnClickListener 
{
    public void onClick( View view ){
        Log.i("MakeMachine", "ButtonClickHandler.onClick()" );
        startCameraActivity();
    }
}

protected void startCameraActivity()
{
    Log.i("MakeMachine", "startCameraActivity()" );
    File file = new File( _path );
    Uri outputFileUri = Uri.fromFile( file );

    Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE );
    intent.putExtra( MediaStore.EXTRA_OUTPUT, outputFileUri );

    startActivityForResult( intent, 0 );
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) 
{   
    Log.i( "MakeMachine", "resultCode: " + resultCode );
    switch( resultCode )
    {
        case 0:
            Log.i( "MakeMachine", "User cancelled" );
            break;

        case -1:
            onPhotoTaken();
            break;
    }
}

protected void onPhotoTaken()
{
    Log.i( "MakeMachine", "onPhotoTaken" );

    _taken = true;

    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inSampleSize = 4;

    Bitmap bitmap = BitmapFactory.decodeFile( _path, options );

    _image.setImageBitmap(bitmap);

    _field.setVisibility( View.GONE );
}

@Override 
protected void onRestoreInstanceState( Bundle savedInstanceState){
    Log.i( "MakeMachine", "onRestoreInstanceState()");
    if( savedInstanceState.getBoolean( PhotoCaptureExample.PHOTO_TAKEN ) ) {
        onPhotoTaken();
    }
}

@Override
protected void onSaveInstanceState( Bundle outState ) {
    outState.putBoolean( PhotoCaptureExample.PHOTO_TAKEN, _taken );
}
}