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"/>

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