Android常用數據類型轉換

String轉int、float、double、byte[]、bitmap

Int i = Integer.parseInt(str);
 
Float f = Float.parseFloat(str);
 
Double d = Double.parseDouble(str);   

//將16進位字元串轉byte數組

public static byte[] hexStringToByte(String str) {
        if(str == null || str.trim().equals("")) {
             return new byte[0];
        }
    　　 byte[] bytes = new byte[str.length() / 2];
        for(int i = 0; i < str.length() / 2; i++) {
            String subStr = str.substring(i * 2, i * 2 + 2);
            bytes[i] = (byte) Integer.parseInt(subStr, 16);
        }
        return bytes;
}

String.format("%04x", i);//將10進位整形轉16進位字元串，%04x2位元組表示不足位補0

//將String字元串轉回Bitmap

public Bitmap stringToBitmap(String string) {
    　　Bitmap bitmap = null;
    　　try {
         　　byte[] bitmapArray;
        　　 bitmapArray = Base64.decode(string, Base64.DEFAULT);
        　　 bitmap = BitmapFactory.decodeByteArray(bitmapArray, 0,bitmapArray.length);
    　　} catch (Exception e) {
        　　e.printStackTrace();
    　　}
    　　return bitmap;
}

 Int轉string、byte[]

String str = String.valueOf(i);//效率最高

//將Int轉byte[]數組

public static byte[] intToBytes2(int n){
      byte[] b = new byte[4];
      for(int i = 0;i < 4;i++){
          b[i] = (byte)(n >> (24 - i * 8)); 
      }
      return b;
}

 Byte[]轉string、int、bitmap

//byte數組轉16進位字元串

private String bytes2HexString(byte[] b, int length) {
      StringBuilder r = new StringBuilder();
      for (int i = 0; i < length; i++) {
           String hex = Integer.toHexString(b[i] & 0xFF);
           if (hex.length() == 1) {
              hex = "0" + hex;
           }
           r.append(hex.toUpperCase());
     }
      return r.toString();
}

//byte數組轉16進位字元串

public static int byteToInt(byte[] b) {
      int mask=0xff;
      int temp=0;
      int n=0;
      for(int i=0;i<b.length;i++){
          n<<=8;
          temp=b[i]&mask;
          n|=temp;
      }
      return n;
}

//byte數組轉bitmap

byte[] b = getIntent().getByteArrayExtra("bitmap");  
Bitmap bitmap = BitmapFactory.decodeByteArray(b, 0, b.length); 


//將byte數組以16進位的形式列印到控制台

public static void printHexString( byte[] b) {
    StringBuilder str= new StringBuilder();
    for (byte aB : b) {
        String hex = Integer.toHexString(aB & 0xFF);
        if (hex.length() == 1) {
            hex = '0' + hex;
        }
        str.append(hex.toUpperCase()).append(" ");
    }
    Log.i("cmd", str.toString());
}

Bitmap轉string、byte[]

//將Bitmap轉base64字元串

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG,90,outputStream );//壓縮90%
byte[] imagebyte = outputStream.toByteArray();
String imageStr = Base64.encode(imagebyte);

//將Bitmap轉byte[]

ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
byte[] datas = baos.toByteArray();

 View轉Bitmap

public static Bitmap view2Bitmap(View view) {
      if (view == null) return null;
      Bitmap ret = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
      Canvas canvas = new Canvas(ret);
      Drawable bgDrawable = view.getBackground();
      if (bgDrawable != null) {
          bgDrawable.draw(canvas);
      } else {
          canvas.drawColor(Color.WHITE);
      }
      view.draw(canvas);
      return ret;
}

 Gson高精度String、Float[]互轉(測試可保留6位數以上)

//Float[]轉String

float feature[] = new float[256];
Gson gson = new Gson();
String str = gson.toJson(feature.clone());

//String高精度還原Float[]

Gson gson = new Gson();
float[] f = gson.fromJson(str, float[].class);

 CRC16檢驗

private int CRC16_Check(byte Pushdata[]){
        int Reg_CRC=0xffff;
        int temp;
        int i,j;
        //幀頭校驗字去掉
        for( i = 2; i<Pushdata.length-2; i ++)
        {
            temp = Pushdata[i];
            if(temp < 0) temp += 256;
            temp &= 0xff;
            Reg_CRC^= temp;

            for (j = 0; j<8; j++)
            {
                if ((Reg_CRC & 0x0001) == 0x0001)
                    Reg_CRC=(Reg_CRC>>1)^0xA001;
                else
                    Reg_CRC >>=1;
            }
        }
        return (Reg_CRC&0xffff);
    }