Android获取文件的MD5值

package my.bag;



import java.io.File;

import java.io.FileInputStream;

import java.math.BigInteger;

import java.security.MessageDigest;

import java.util.HashMap;

import java.util.Map;



import android.app.Activity;

import android.os.Bundle;

import android.util.Log;



public class FileDigest extends Activity {



 @Override

 protected void onCreate(Bundle savedInstanceState) {

  // TODO Auto-generated method stub

  super.onCreate(savedInstanceState);

  File file = new File("/mnt/sdcard/123.txt");

  Log.e("MD5", getFileMD5(file));

 }



 /**

  * 获取单个文件的MD5值！



  * @param file

  * @return

  */



 public static String getFileMD5(File file) {

  if (!file.isFile()) {

   return null;

  }

  MessageDigest digest = null;

  FileInputStream in = null;

  byte buffer[] = new byte[1024];

  int len;

  try {

   digest = MessageDigest.getInstance("MD5");

   in = new FileInputStream(file);

   while ((len = in.read(buffer, 0, 1024)) != -1) {

    digest.update(buffer, 0, len);

   }

   in.close();

  } catch (Exception e) {

   e.printStackTrace();

   return null;

  }

  BigInteger bigInt = new BigInteger(1, digest.digest());

  return bigInt.toString(16);

 }



 /**

  * 获取文件夹中文件的MD5值

  * 

  * @param file

  * @param listChild

  *            ;true递归子目录中的文件

  * @return

  */

 public static Map<String, String> getDirMD5(File file, boolean listChild) {

  if (!file.isDirectory()) {

   return null;

  }

  Map<String, String> map = new HashMap<String, String>();

  String md5;

  File files[] = file.listFiles();

  for (int i = 0; i < files.length; i++) {

   File f = files[i];

   if (f.isDirectory() && listChild) {

    map.putAll(getDirMD5(f, listChild));

   } else {

    md5 = getFileMD5(f);

    if (md5 != null) {

     map.put(f.getPath(), md5);

    }

   }

  }

  return map;

 }



}



最后不要忘了在manifest中添加权限



<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

package my.bag;



import java.io.File;

import java.io.FileInputStream;

import java.math.BigInteger;

import java.security.MessageDigest;

import java.util.HashMap;

import java.util.Map;



import android.app.Activity;

import android.os.Bundle;

import android.util.Log;



public class FileDigest extends Activity {



 @Override

 protected void onCreate(Bundle savedInstanceState) {

  // TODO Auto-generated method stub

  super.onCreate(savedInstanceState);

  File file = new File("/mnt/sdcard/123.txt");

  Log.e("MD5", getFileMD5(file));

 }



 /**

  * 获取单个文件的MD5值！



  * @param file

  * @return

  */



 public static String getFileMD5(File file) {

  if (!file.isFile()) {

   return null;

  }

  MessageDigest digest = null;

  FileInputStream in = null;

  byte buffer[] = new byte[1024];

  int len;

  try {

   digest = MessageDigest.getInstance("MD5");

   in = new FileInputStream(file);

   while ((len = in.read(buffer, 0, 1024)) != -1) {

    digest.update(buffer, 0, len);

   }

   in.close();

  } catch (Exception e) {

   e.printStackTrace();

   return null;

  }

  BigInteger bigInt = new BigInteger(1, digest.digest());

  return bigInt.toString(16);

 }



 /**

  * 获取文件夹中文件的MD5值

  * 

  * @param file

  * @param listChild

  *            ;true递归子目录中的文件

  * @return

  */

 public static Map<String, String> getDirMD5(File file, boolean listChild) {

  if (!file.isDirectory()) {

   return null;

  }

  Map<String, String> map = new HashMap<String, String>();

  String md5;

  File files[] = file.listFiles();

  for (int i = 0; i < files.length; i++) {

   File f = files[i];

   if (f.isDirectory() && listChild) {

    map.putAll(getDirMD5(f, listChild));

   } else {

    md5 = getFileMD5(f);

    if (md5 != null) {

     map.put(f.getPath(), md5);

    }

   }

  }

  return map;

 }



}



最后不要忘了在manifest中添加权限



<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>