Android--判斷文字檔編碼

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方法1：利用windows文字檔編碼特點。

windows下，Unicode、Unicode big endian和UTF-8編碼的txt檔案的開頭會多出幾個位元組，分別是FF、FE（Unicode）,FE、FF（Unicode big endian）,EF、BB、BF（UTF-8）。

public static String getCharset(File file) {        String charset = "GBK";        byte[] first3Bytes = new byte[3];        try {            boolean checked = false;            BufferedInputStream bis = new BufferedInputStream(                  new FileInputStream(file));            bis.mark(0);            int read = bis.read(first3Bytes, 0, 3);            if (read == -1)                return charset;            if (first3Bytes[0] == (byte) 0xFF && first3Bytes[1] == (byte) 0xFE) {                charset = "UTF-16LE";                checked = true;            } else if (first3Bytes[0] == (byte) 0xFE && first3Bytes[1]                == (byte) 0xFF) {                charset = "UTF-16BE";                checked = true;            } else if (first3Bytes[0] == (byte) 0xEF && first3Bytes[1]                    == (byte) 0xBB                    && first3Bytes[2] == (byte) 0xBF) {                charset = "UTF-8";                checked = true;            }            bis.reset();            if (!checked) {                int loc = 0;                while ((read = bis.read()) != -1) {                    loc++;                    if (read >= 0xF0)                        break;                    //單獨出現BF以下的，也算是GBK                    if (0x80 <= read && read <= 0xBF)                        break;                    if (0xC0 <= read && read <= 0xDF) {                        read = bis.read();                        if (0x80 <= read && read <= 0xBF)// 雙位元組 (0xC0 - 0xDF)                            // (0x80 -                            // 0xBF),也可能在GB編碼內                            continue;                        else                            break;                     // 也有可能出錯，但是幾率較小                    } else if (0xE0 <= read && read <= 0xEF) {                        read = bis.read();                        if (0x80 <= read && read <= 0xBF) {                            read = bis.read();                            if (0x80 <= read && read <= 0xBF) {                                charset = "UTF-8";                                break;                            } else                                break;                        } else                            break;                    }                }                System.out.println(loc + " " + Integer.toHexString(read));            }            bis.close();        } catch (Exception e) {            e.printStackTrace();        }        return charset;    }

缺點：不能這樣去探測linux下的檔案。

方法2：開源工程 JCharDet

http://www.iteye.com/topic/266501

package org.mozilla.intl.chardet;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;/** * 藉助JCharDet擷取檔案字元集 * @author icer * PS: * JCharDet 是mozilla自動字元集探測演算法代碼的java移植，其官方首頁為： *      http://jchardet.sourceforge.net/ * @date2008/11/13  */public class FileCharsetDetector {private boolean found = false;/** * 如果完全符合某個字元集檢測演算法, 則該屬性儲存該字元集的名稱. 否則(如二進位檔案)其值就為預設值 null, 這時應當查詢屬性  */private String encoding = null;public static void main(String[] argv) throws Exception {if (argv.length != 1 && argv.length != 2) {System.out.println("Usage: FileCharsetDetector <path> [<languageHint>]");System.out.println("");System.out.println("Where <path> is d:/demo.txt");System.out.println("For optional <languageHint>. Use following...");System.out.println("1 => Japanese");System.out.println("2 => Chinese");System.out.println("3 => Simplified Chinese");System.out.println("4 => Traditional Chinese");System.out.println("5 => Korean");System.out.println("6 => Dont know (default)");return;} else {String encoding = null;if (argv.length == 2) {encoding = new FileCharsetDetector().guestFileEncoding(argv[0],Integer.valueOf(argv[1]));} else {encoding = new FileCharsetDetector().guestFileEncoding(argv[0]);}System.out.println("檔案編碼:" + encoding);}}/** * 傳入一個檔案(File)對象，檢查檔案編碼 *  * @param file *            File對象執行個體 * @return 檔案編碼，若無，則返回null * @throws FileNotFoundException * @throws IOException */public String guestFileEncoding(File file) throws FileNotFoundException,IOException {return geestFileEncoding(file, new nsDetector());}/** * 擷取檔案的編碼 *  * @param file *            File對象執行個體 * @param languageHint *            語言提示地區代碼 eg：1 : Japanese; 2 : Chinese; 3 : Simplified Chinese; *            4 : Traditional Chinese; 5 : Korean; 6 : Dont know (default) * @return 檔案編碼，eg：UTF-8,GBK,GB2312形式，若無，則返回null * @throws FileNotFoundException * @throws IOException */public String guestFileEncoding(File file, int languageHint)throws FileNotFoundException, IOException {return geestFileEncoding(file, new nsDetector(languageHint));}/** * 擷取檔案的編碼 *  * @param path *            檔案路徑 * @return 檔案編碼，eg：UTF-8,GBK,GB2312形式，若無，則返回null * @throws FileNotFoundException * @throws IOException */public String guestFileEncoding(String path) throws FileNotFoundException,IOException {return guestFileEncoding(new File(path));}/** * 擷取檔案的編碼 *  * @param path *            檔案路徑 * @param languageHint *            語言提示地區代碼 eg：1 : Japanese; 2 : Chinese; 3 : Simplified Chinese; *            4 : Traditional Chinese; 5 : Korean; 6 : Dont know (default) * @return * @throws FileNotFoundException * @throws IOException */public String guestFileEncoding(String path, int languageHint)throws FileNotFoundException, IOException {return guestFileEncoding(new File(path), languageHint);}/** * 擷取檔案的編碼 *  * @param file * @param det * @return * @throws FileNotFoundException * @throws IOException */private String geestFileEncoding(File file, nsDetector det)throws FileNotFoundException, IOException {// Set an observer...// The Notify() will be called when a matching charset is found.det.Init(new nsICharsetDetectionObserver() {public void Notify(String charset) {found = true;encoding = charset;}});BufferedInputStream imp = new BufferedInputStream(new FileInputStream(file));byte[] buf = new byte[1024];int len;boolean done = false;boolean isAscii = true;while ((len = imp.read(buf, 0, buf.length)) != -1) {// Check if the stream is only ascii.if (isAscii)isAscii = det.isAscii(buf, len);// DoIt if non-ascii and not done yet.if (!isAscii && !done)done = det.DoIt(buf, len, false);}det.DataEnd();if (isAscii) {encoding = "ASCII";found = true;}if (!found) {String prob[] = det.getProbableCharsets();if (prob.length > 0) {// 在沒有發現情況下，則取第一個可能的編碼encoding = prob[0];} else {return null;}}return encoding;}}

jar包：http://download.csdn.net/detail/u012587637/8041169

方法3：開源工程juniversalcharde

http://code.google.com/p/juniversalchardet/ 

public static String getFileIncode(File file) {if (!file.exists()) {System.err.println("getFileIncode: file not exists!");return null;}byte[] buf = new byte[4096];FileInputStream fis = null;try {fis = new FileInputStream(file);// (1)UniversalDetector detector = new UniversalDetector(null);// (2)int nread;while ((nread = fis.read(buf)) > 0 && !detector.isDone()) {detector.handleData(buf, 0, nread);}// (3)detector.dataEnd();// (4)String encoding = detector.getDetectedCharset();if (encoding != null) {System.out.println("Detected encoding = " + encoding);} else {System.out.println("No encoding detected.");}// (5)detector.reset();fis.close();return encoding;} catch (Exception e) {e.printStackTrace();}return null;}

引入包的方法：

將包放入libs檔案夾，

選中包，右鍵 --> build path--> add to build path。

jar包下載：http://download.csdn.net/detail/u012587637/8041181

說明：第三個方法要比第二個速度快些，也比較新，所以推薦使用第三個。

Android--判斷文字檔編碼