Android--判斷文字檔案編碼
阿新 • • 發佈：2019-02-01
方法1：利用windows文字檔案編碼特點。
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，但是機率較小 } 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
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獲取檔案字符集 * @author icer * PS: * JCharDet 是mozilla自動字符集探測演算法程式碼的java移植，其官方主頁為： * http://jchardet.sourceforge.net/ * @date 2008/11/13 */ public class FileCharsetDetector { private boolean found = false; /** * 如果完全匹配某個字符集檢測演算法, 則該屬性儲存該字符集的名稱. 否則(如二進位制檔案)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)物件，檢查檔案編碼 * * @param file * File物件例項 * @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()); } /** * 獲取檔案的編碼 * * @param file * File物件例項 * @param languageHint * 語言提示區域程式碼 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)); } /** * 獲取檔案的編碼 * * @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)); } /** * 獲取檔案的編碼 * * @param path * 檔案路徑 * @param languageHint * 語言提示區域程式碼 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); } /** * 獲取檔案的編碼 * * @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; } }
方法3：開源工程juniversalcharde
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資料夾，
選中包，右鍵 --> build path--> add to build path。
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。