遍历SD卡取文件

public class TextActivity extends Activity {

    Gallery g = null;
    List<String> it = null;// 遍历符合条件的列表
    public String actionUrl = null;

    private final String SD_PATH = android.os.Environment

                  .getExternalStorageDirectory().getAbsolutePath();

    public void onCreate(Bundle savedInstanceState) {

           super.onCreate(savedInstanceState);
           setContentView(R.layout.location_photo);
           g = (Gallery) findViewById(R.id.mygallery);
           //添加一个ImageAdapter并设置给Gallery对象
           g.setAdapter(new ImageAdapter(this, getSD()));
           //设置一个itemclickListener并Toast被单击图片的位置
           g.setOnItemClickListener(new OnItemClickListener() {
                  public void onItemClick(AdapterView<?> parent, View v,
                                int position, long id) {
                         Toast.makeText(TextActivity.this,
                                       "序列：" + (position + 1) + "\n路径：" + it.get(position),
                                       Toast.LENGTH_LONG).show();
                  }
           });
    }

//遍历SD卡中某一路径下指定类型的图片
    private List<String> getSD() {
           it = new ArrayList<String>();
           File f = new File(SD_PATH + "//" + "picture");
           File[] files = f.listFiles();

           for (int i = 0; i < files.length; i++) {
                  File file = files[i];
                  if (getImageFile(file.getPath()))
                         it.add(file.getPath());
           }
           return it;
    }

//指定遍历文件类型
    private boolean getImageFile(String fName) {
           boolean re;
           String end = fName
                         .substring(fName.lastIndexOf(".") + 1, fName.length())
                         .toLowerCase();

　　//toLowerCase 方法 返回一个字符串，该字符串中的字母被转换为小写字母。
           if (end.equals("jpg") || end.equals("gif") || end.equals("png")
                         || end.equals("jpeg") || end.equals("bmp")) {
                  re = true;
           } else {
                  re = false;
           }
           return re;
    }

    //改写BaseAdapter自定义一ImageAdapter class
    public class ImageAdapter extends BaseAdapter {
           int mGalleryItemBackground;
           private Context mContext;
           private List<String> lis;
           public ImageAdapter(Context c, List<String> li) {
                  mContext = c;
                  lis = li;
                  //使用在res/values/aatrs.xml中的<declare-styleable>定义
                  TypedArray a = obtainStyledAttributes(R.styleable.Gallery);
                  //取得Gallery属性
                  mGalleryItemBackground = a.getResourceId(
                                R.styleable.Gallery_android_galleryItemBackground, 0);
                  //让对象的styleable属性能够反复使用
                  a.recycle();
           }
           //重写的方法，返回图片数目
           public int getCount() {
                  return lis.size();
           }
           //重写的方法，返回图片的数组id
           public Object getItem(int position) {
                  return position;
           }
           public long getItemId(int position) {
                  return position;
           }
           //重写的方法，返回一View对象
           public View getView(int position, View convertView, ViewGroup parent) {
                   //产生ImageView对象
                  ImageView i = new ImageView(mContext);
                  //设置图片给ImageView对象
                  Bitmap bm = BitmapFactory.decodeFile(lis.get(position).toString());
                  i.setImageBitmap(bm);
                  //重新设置图片的宽度
                  i.setScaleType(ImageView.ScaleType.FIT_XY);
                  //重新设置Layout的宽度
                  i.setLayoutParams(new Gallery.LayoutParams(188, 288));
                  //设置Callery背景图
                  i.setBackgroundResource(mGalleryItemBackground);
                  return i;
           }
    }
}

===================================================================================

2.attrs.xml

<?xml version="1.0" encoding="utf-8"?> 
<resources>   
　　<declare-styleable name="Gallery">     
　　　　<attr name="android:galleryItemBackground" />   
　　</declare-styleable>  
</resources>