Android根据文件路径加载指定文件

public class Util {
    
    /****
     * 计算文件大小
     * 
     * @param length
     * @return
     */
    public static String ShowLongFileSzie(Long length) {
        if (length >= 1048576) {
            return (length / 1048576) + "MB";
        } else if (length >= 1024) {
            return (length / 1024) + "KB";
        } else if (length < 1024) {
            return length + "B";
        } else {
            return "0KB";
        }
    }
    
    /***
     * 
     * 更具路径得到该路径下的全部图片信息
     * @return
     */
    
    public static List<AddFileInfo> getSDPathFrom() {
        // 图片列表
        List<AddFileInfo> imagePathList = new ArrayList<AddFileInfo>();
        // 得到sd卡内image文件夹的路径 
        String filePath = Environment.getExternalStorageDirectory().toString() + File.separator+"BigNoxHD/cache/";
        //得到该路径文件夹下所有的文件
        File fileAll = new File(filePath);
        File[] files = fileAll.listFiles();
        // 将所有的文件存入ArrayList中,并过滤所有图片格式的文件
        for (int i = 0; i < files.length; i++) {
            File file = files[i];
            if (checkIsFile(file.getPath())) {
                String time = new SimpleDateFormat("yyyy-MM-dd")
                .format(new Date(file.lastModified()));
                AddFileInfo info=new AddFileInfo(file.getName(), Util.ShowLongFileSzie(file.length()), time, file.getAbsolutePath());
                imagePathList.add(info);
            }
        }
        // 返回得到的图片列表
        return imagePathList;
    }

    /****
     * 验证文件格式
     * @param fName
     * @return
     */
    public static boolean checkIsFile(String fName) {
        boolean isImageFile = false;
        // 获取扩展名
        String FileEnd = fName.substring(fName.lastIndexOf(".") + 1,
                fName.length()).toLowerCase();
        if (FileEnd.equals("jpg") || FileEnd.equals("png") || FileEnd.equals("gif")|| FileEnd.equals("jpeg") ) {
            isImageFile = true;
        } else {
            isImageFile = false;
        }
        return isImageFile;
    }
    
    /****
     * 根据文件路径获取图片
     * 其中w和h你需要转换的大小
     * @param path 
     * @param w
     * @param h
     * @return
     */
    public static Bitmap convertToBitmap(String path, int w, int h) {
        BitmapFactory.Options opts = new BitmapFactory.Options();
        // 设置为ture只获取图片大小
        opts.inJustDecodeBounds = true;
        opts.inPreferredConfig = Bitmap.Config.ARGB_8888;
        // 返回为空
        BitmapFactory.decodeFile(path, opts);
        int width = opts.outWidth;
        int height = opts.outHeight;
        float scaleWidth = 0.f, scaleHeight = 0.f;
        if (width > w || height > h) {
            // 缩放
            scaleWidth = ((float) width) / w;
            scaleHeight = ((float) height) / h;
        }
        opts.inJustDecodeBounds = false;
        float scale = Math.max(scaleWidth, scaleHeight);
        opts.inSampleSize = (int)scale;
        WeakReference<Bitmap> weak = new WeakReference<Bitmap>(BitmapFactory.decodeFile(path, opts));
        return Bitmap.createScaledBitmap(weak.get(), w, h, true);
    }
}

public class MainActivity extends Activity {

    private ListView mListview;
    private List<AddFileInfo> list;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    private void initView() {
        // TODO Auto-generated method stub
        mListview = (ListView) findViewById(R.id.listview);
        list = Util.getSDPathFrom();
        mListview.setAdapter(new Adapter(MainActivity.this));
    }

    class Adapter extends BaseAdapter {
        private LayoutInflater inflater;
        private Context context;

        public Adapter(Context context) {
            this.context = context;
            this.inflater = LayoutInflater.from(context);
        }

        @Override
        public int getCount() {
            return list.size();
        }

        @Override
        public Object getItem(int position) {
            return list.get(position);
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if (null == convertView) {
                convertView = inflater.inflate(
                        R.layout.item_mytask_file_listview, null);
                holder = new ViewHolder(convertView);
                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }
            AddFileInfo info = (AddFileInfo) getItem(position);
            holder.img.setImageBitmap(Util.convertToBitmap(info.getPath(), 99, 99));
            holder.tv_name.setText("文件名称：" + info.getName());
            holder.size.setText("文件大小：" + info.getSize());
            holder.time.setText("文件创建时间：" + info.getTime());
            return convertView;
        }

    }

    class ViewHolder {

        private TextView tv_name;
        private TextView size;
        private TextView time;
        private ImageView img;

        public ViewHolder(View view) {
            img = (ImageView) view.findViewById(R.id.img);
            tv_name = (TextView) view.findViewById(R.id.item_file_name);
            size = (TextView) view.findViewById(R.id.item_file_size);
            time = (TextView) view.findViewById(R.id.item_file_time);
        }
    }
}

 <!-- SD卡权限 -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />