Java tutorial
//package com.java2s; import java.io.File; import java.io.RandomAccessFile; import android.util.Log; public class Main { private static final String TAG = "SDK_WeiXin.Util"; public static byte[] readFromFile(String fileName, int offset, int len) { if (fileName == null) { return null; } File file = new File(fileName); if (!file.exists()) { Log.i(TAG, "readFromFile: file not found"); return null; } if (len == -1) { len = (int) file.length(); } Log.d(TAG, "readFromFile : offset = " + offset + " len = " + len + " offset + len = " + (offset + len)); if (offset < 0) { Log.e(TAG, "readFromFile invalid offset:" + offset); return null; } if (len <= 0) { Log.e(TAG, "readFromFile invalid len:" + len); return null; } if (offset + len > (int) file.length()) { Log.e(TAG, "readFromFile invalid file len:" + file.length()); return null; } byte[] b = null; try { RandomAccessFile in = new RandomAccessFile(fileName, "r"); b = new byte[len]; in.seek(offset); in.readFully(b); in.close(); } catch (Exception e) { Log.e(TAG, "readFromFile : errMsg = " + e.getMessage()); e.printStackTrace(); } return b; } }