图片从数据流转换为字符型，方便网络传输 base64转换 【转】

ndroid不能直接利用java里的base64类，需要自己定义编写一个编码类，从而达到可以在网络中传输照片的目的，以下就是构建一个编码类型，便于进行网络传输。

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构建一个base64类：

public class base64 {
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?private static final byte[] encodingTable = { (byte) 'A', (byte) 'B',
???(byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
???(byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L',
???(byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q',
???(byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V',
???(byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a',
???(byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
???(byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k',
???(byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
???(byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
???(byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
???(byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4',
???(byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
???(byte) '+', (byte) '/' };

?private static final byte[] decodingTable;

?static {
??decodingTable = new byte[128];
??for (int i = 0; i < 128; i++) {
???decodingTable[i] = (byte) -1;
??}
??for (int i = 'A'; i <= 'Z'; i++) {
???decodingTable[i] = (byte) (i - 'A');
??}
??for (int i = 'a'; i <= 'z'; i++) {
???decodingTable[i] = (byte) (i - 'a' + 26);
??}
??for (int i = '0'; i <= '9'; i++) {
???decodingTable[i] = (byte) (i - '0' + 52);
??}
??decodingTable['+'] = 62;
??decodingTable['/'] = 63;
?}

?public static byte[] encode(byte[] data) {
??byte[] bytes;
??int modulus = data.length % 3;
??if (modulus == 0) {
???bytes = new byte[(4 * data.length) / 3];
??} else {
???bytes = new byte[4 * ((data.length / 3) + 1)];
??}
??int dataLength = (data.length - modulus);
??int a1;
??int a2;
??int a3;
??for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
???a1 = data[i] & 0xff;
???a2 = data[i + 1] & 0xff;
???a3 = data[i + 2] & 0xff;
???bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
???bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
???bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
???bytes[j + 3] = encodingTable[a3 & 0x3f];
??}
??int b1;
??int b2;
??int b3;
??int d1;
??int d2;
??switch (modulus) {
??case 0: /* nothing left to do */
???break;
??case 1:
???d1 = data[data.length - 1] & 0xff;
???b1 = (d1 >>> 2) & 0x3f;
???b2 = (d1 << 4) & 0x3f;
???bytes[bytes.length - 4] = encodingTable[b1];
???bytes[bytes.length - 3] = encodingTable[b2];
???bytes[bytes.length - 2] = (byte) '=';
???bytes[bytes.length - 1] = (byte) '=';
???break;
??case 2:
???d1 = data[data.length - 2] & 0xff;
???d2 = data[data.length - 1] & 0xff;
???b1 = (d1 >>> 2) & 0x3f;
???b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
???b3 = (d2 << 2) & 0x3f;
???bytes[bytes.length - 4] = encodingTable[b1];
???bytes[bytes.length - 3] = encodingTable[b2];
???bytes[bytes.length - 2] = encodingTable[b3];
???bytes[bytes.length - 1] = (byte) '=';
???break;
??}
??return bytes;
?}

?public static byte[] decode(byte[] data) {
??byte[] bytes;
??byte b1;
??byte b2;
??byte b3;
??byte b4;
??data = discardNonBase64Bytes(data);
??if (data[data.length - 2] == '=') {
???bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
??} else if (data[data.length - 1] == '=') {
???bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
??} else {
???bytes = new byte[((data.length / 4) * 3)];
??}
??for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) {
???b1 = decodingTable[data[i]];
???b2 = decodingTable[data[i + 1]];
???b3 = decodingTable[data[i + 2]];
???b4 = decodingTable[data[i + 3]];
???bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
???bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
???bytes[j + 2] = (byte) ((b3 << 6) | b4);
??}
??if (data[data.length - 2] == '=') {
???b1 = decodingTable[data[data.length - 4]];
???b2 = decodingTable[data[data.length - 3]];
???bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
??} else if (data[data.length - 1] == '=') {
???b1 = decodingTable[data[data.length - 4]];
???b2 = decodingTable[data[data.length - 3]];
???b3 = decodingTable[data[data.length - 2]];
???bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
???bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
??} else {
???b1 = decodingTable[data[data.length - 4]];
???b2 = decodingTable[data[data.length - 3]];
???b3 = decodingTable[data[data.length - 2]];
???b4 = decodingTable[data[data.length - 1]];
???bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
???bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
???bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
??}
??return bytes;
?}

?public static byte[] decode(String data) {
??byte[] bytes;
??byte b1;
??byte b2;
??byte b3;
??byte b4;
??data = discardNonBase64Chars(data);
??if (data.charAt(data.length() - 2) == '=') {
???bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
??} else if (data.charAt(data.length() - 1) == '=') {
???bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
??} else {
???bytes = new byte[((data.length() / 4) * 3)];
??}
??for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) {
???b1 = decodingTable[data.charAt(i)];
???b2 = decodingTable[data.charAt(i + 1)];
???b3 = decodingTable[data.charAt(i + 2)];
???b4 = decodingTable[data.charAt(i + 3)];
???bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
???bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
???bytes[j + 2] = (byte) ((b3 << 6) | b4);
??}
??if (data.charAt(data.length() - 2) == '=') {
???b1 = decodingTable[data.charAt(data.length() - 4)];
???b2 = decodingTable[data.charAt(data.length() - 3)];
???bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
??} else if (data.charAt(data.length() - 1) == '=') {
???b1 = decodingTable[data.charAt(data.length() - 4)];
???b2 = decodingTable[data.charAt(data.length() - 3)];
???b3 = decodingTable[data.charAt(data.length() - 2)];
???bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
???bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
??} else {
???b1 = decodingTable[data.charAt(data.length() - 4)];
???b2 = decodingTable[data.charAt(data.length() - 3)];
???b3 = decodingTable[data.charAt(data.length() - 2)];
???b4 = decodingTable[data.charAt(data.length() - 1)];
???bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
???bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
???bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
??}
??return bytes;
?}

?private static byte[] discardNonBase64Bytes(byte[] data) {
??byte[] temp = new byte[data.length];
??int bytesCopied = 0;
??for (int i = 0; i < data.length; i++) {
???if (isValidBase64Byte(data[i])) {
????temp[bytesCopied++] = data[i];
???}
??}
??byte[] newData = new byte[bytesCopied];
??System.arraycopy(temp, 0, newData, 0, bytesCopied);
??return newData;
?}

?private static String discardNonBase64Chars(String data) {
??StringBuffer sb = new StringBuffer();
??int length = data.length();
??for (int i = 0; i < length; i++) {
???if (isValidBase64Byte((byte) (data.charAt(i)))) {
????sb.append(data.charAt(i));
???}
??}
??return sb.toString();
?}

?private static boolean isValidBase64Byte(byte b) {
??if (b == '=') {
???return true;
??} else if ((b < 0) || (b >= 128)) {
???return false;
??} else if (decodingTable[b] == -1) {
???return false;
??}
??return true;
?}
}

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转换的实例为：

public static String ReadFile(File file) {
??String result = "";
??FileInputStream fis = null;
??byte[] xml = null;
??try {
???if (file != null) {
????fis = new FileInputStream(file);
????if (fis != null) {
?????int len = fis.available();
?????xml = new byte[len];
?????fis.read(xml);
????}
????base64 enc = new base64();
????byte[] bb = enc.encode(xml);
????result = new String(bb,"UTF-8");
???}
??} catch (IOException e) {
???e.printStackTrace();
??} finally {
???if(fis!=null){
????try {
?????fis.close();
?????fis = null;
????} catch (IOException e) {
?????// TODO Auto-generated catch block
?????e.printStackTrace();
????}
???}
??}
??return result;
?}

此时的result即为转换后的字符型，解析的时候按照java的base64解析即可