java - 尝试创建一种在 Android Java 中格式化十六进制字符串的方法

Question

我正在尝试创建一种方法来格式化十六进制字符串并将该字符串分解为每 2 个字符等于一个字节。我想要一个三个字节数组，例如该字符串是“012254”，然后是“01”、“22”、“54”。我已经创建了这些方法，但我收到一个“NumberFormatException”，提示 Invalid int: ""。任何人都可以查看我的代码并查看 logcat，看看我可以采取哪些措施来解决该问题。预先感谢您。

这是代码:

/*
 * Converts a set of hex digits into an array of 8-bit binary bytes.
 * Stops at the first non-hex character if before the end of the string.
 * Hex bytes are assumed to be pairs of digits i.e. least significant byte (LSB) -> most significant byte (MSB) with most significant nibble first.
 * e.g. for a string: "F20C345A" will convert to values F2,0C,34,5A.
 * Adds zeroes to the end of the string to make last digits up to the length for a byte.
 */
public byte[] toByteArray(String hexString)
{   
    int offSet = 0;
    int hexLength = 0;
    int bytes = 0;
    String byteString = "";
    byte[] byteArray;

    hexLength = hexSequenceLength(hexString); // Check for hex sequence.
    hexString = hexString.substring(0, hexLength); // Ignore anything after hex sequence.

    bytes = hexLength / CHARSPERBYTE; // Calculate how many words are represented by the string.

    int rem = hexLength % CHARSPERBYTE;

    if(rem != 0)
    {
        /*
         * Hex string is too short.
         * Add padding zeroes to fill up to boundary of a complete word.
         */
        int paddingZeroes = CHARSPERBYTE - rem;

        if((paddingZeroes & (int)0x01) != 0)
        {
            /*
             * Odd number of padding zeroes.
             * This means that the first zero must be inserted before the last digit to keep it the least significant nibble (4-bit).
             */
            hexString = new StringBuilder(hexString).insert(hexLength-1, "0").toString();

            paddingZeroes--;
        }

        /* Add zeroes to the end of the string so that MSB's of last value will be zero. */
        for(int i=0; i<paddingZeroes; i++)
        {
            hexString += "0";
        }

        /* Recalculate length. */
        hexLength = hexSequenceLength(hexString);
        bytes = hexLength / CHARSPERBYTE;
    }

    if(bytes > 0)
    {
        byteArray = new byte[bytes]; // Set up array to receive these values.

        for(int i=0; i<bytes; i++)
        {
            byteString = hexSubString(hexString, offSet, CHARSPERBYTE, false); // Isolate digits for a single byte.

            byteArray[i] = (byte)Integer.parseInt(byteString, 16); // Parse value into binary data array.

            offSet += CHARSPERBYTE; // Set up for next word hex.    
        }

        byte subSystem = byteArray[0];
        byte highLevel = byteArray[1];
        byte lowLevel = byteArray[2];
        String bytesValue = new String(byteArray);

        System.out.println("Byte array size: " + byteArray.length);
        System.out.println("Byte 1: " + subSystem);
        System.out.println("Byte 2: " + highLevel);
        System.out.println("Byte 3: " + lowLevel);
        System.out.println("Byte array value: " + bytesValue);
        // TODO: Need to get the actual value of the bytes, the result just returns 16.
    }
    else
    {
        byteArray = new byte[0]; // No hex data.

        //throw new HexException();
    }

    return byteArray;
}

/*
 * Isolates a HEX value sub-string from the given HEX character string from its start index and character length.
 * Includes option to re-order digit pairs to change the order of significance of bytes in a HEX number.
 */
private String hexSubString(String src, int index, int length, boolean reverse)
{
    int hexNumbers = length / CHARSPERBYTE;
    String[] hexNumber = new String[hexNumbers];
    int numberIndex = index;
    String hexSubString = "";

    for(int i=0; i<hexNumbers; i++)
    {   
        hexNumber[i] = src.substring(numberIndex, CHARSPERBYTE+2);
        numberIndex += CHARSPERBYTE;

        if(numberIndex > src.length())
        {
            break;
        }
    }

    if(reverse == false)
    {
        for(int i=0; i<hexNumbers; i++)
        {
            hexSubString += hexNumber[i];
        }
    }
    else
    {
        // Reverse order to make MSB -> LSB.
        for(int i=hexNumbers; i>0; i--)
        {
            hexSubString += hexNumber[i-1];
        }
    }

    return hexSubString;
}

/*
 * Gets the number of consecutive hex characters from start of string.
 */
private int hexSequenceLength(String hexString)
{
    int length = 0;

    char[] charArray = hexString.toCharArray();

    for(char c : charArray)
    {
        if(hexChecker(c))
        {
            length++;
        }
        else
        {
            break;
        }   
    }

    return length;
}

/*
 * Checks if character is valid against HEX values.
 */
private boolean hexChecker(char c)
{
    String hexValues = "0123456789abcdefABCDEF";

    if(hexValues.indexOf(c) > -1 == true)
    {
        System.out.println("It worked!");
    }
    else
    {
        System.out.println("It did not work!");
    }

    return hexValues.indexOf(c) > -1;
}

这是日志猫:

10-07 11:53:11.420: E/AndroidRuntime(4440): FATAL EXCEPTION: main
10-07 11:53:11.420: E/AndroidRuntime(4440): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mobileapplicationretry/com.example.mobileapplicationretry.MainActivity}: java.lang.NumberFormatException: Invalid int: ""
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.os.Looper.loop(Looper.java:137)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.ActivityThread.main(ActivityThread.java:5103)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at java.lang.reflect.Method.invokeNative(Native Method)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at java.lang.reflect.Method.invoke(Method.java:525)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at dalvik.system.NativeStart.main(Native Method)
10-07 11:53:11.420: E/AndroidRuntime(4440): Caused by: java.lang.NumberFormatException: Invalid int: ""
10-07 11:53:11.420: E/AndroidRuntime(4440):     at java.lang.Integer.invalidInt(Integer.java:138)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at java.lang.Integer.parseInt(Integer.java:359)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at com.example.mobileapplicationretry.devicedescription.HexFunctions.toByteArray(HexFunctions.java:73)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at com.example.mobileapplicationretry.devicedescription.DeviceValues.setUpValues(DeviceValues.java:76)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at com.example.mobileapplicationretry.devicedescription.DeviceDescriptionDataSet.setUpDataSet(DeviceDescriptionDataSet.java:239)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at com.example.mobileapplicationretry.MainActivity.onCreate(MainActivity.java:59)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.Activity.performCreate(Activity.java:5133)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-07 11:53:11.420: E/AndroidRuntime(4440):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
10-07 11:53:11.420: E/AndroidRuntime(4440):     ... 11 more

Answer 1

为什么不使用现有的类来做到这一点？

String myHexStr = "AB1257";
int hexInt = Integer.parseInt(myHexStr, 16);
ByteBuffer buffer = ByteBuffer.allocate(4);
buffer.putInt(hexInt);
byte[] result = buffer.array();

如果您想创建一个 3 的数组，只需将结果数组复制到一个新的较小数组即可。您唯一需要弄清楚的是您要丢弃哪个字节:第一个字节(MSB)或最后一个字节(LSB):

byte[] threeByteArray = new byte[3];

int start = useMSB ? 0 : 1;
for (int i = start; i < threeByteArray.length; i++)
    threeByteArray[i - start] = result[i];

希望这有帮助:)