Android小技巧总结1

        SimpleDateFormat formatter = new SimpleDateFormat(
                "yyyy年MM月dd日   HH:mm:ss");
        Date curDate = new Date(System.currentTimeMillis());// 获取当前时间
        String str = formatter.format(curDate);

    String label = DateUtils.formatDateTime( 
            getApplicationContext(), 
            System.currentTimeMillis(), 
            DateUtils.FORMAT_SHOW_TIME 
                    | DateUtils.FORMAT_SHOW_DATE 
                    | DateUtils.FORMAT_ABBREV_ALL);

private final static int[] li_SecPosValue = { 1601, 1637, 1833, 2078, 2274,
        2302, 2433, 2594, 2787, 3106, 3212, 3472, 3635, 3722, 3730, 3858,
        4027, 4086, 4390, 4558, 4684, 4925, 5249, 5590 };
private final static String[] lc_FirstLetter = { "A", "B", "C", "D", "E",
        "F", "G", "H", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S",
        "T", "W", "X", "Y", "Z" };
// 获得每一个string的首字母
/**
 * 取得给定汉字的首字母,即声母
 * @param chinese 给定的汉字
 * @return 给定汉字的声母
 */
public String getFirstLetter(String chinese) {
    if (chinese == null || chinese.trim().length() == 0) {
        return "";
    }
    chinese = this.conversionStr(chinese, "GB2312", "ISO8859-1");

    if (chinese.length() > 1) { // 推断是不是汉字
        int li_SectorCode = (int) chinese.charAt(0); // 汉字区码
        int li_PositionCode = (int) chinese.charAt(1); // 汉字位码
        li_SectorCode = li_SectorCode - 160;
        li_PositionCode = li_PositionCode - 160;
        int li_SecPosCode = li_SectorCode * 100 + li_PositionCode; // 汉字区位码
        if (li_SecPosCode > 1600 && li_SecPosCode < 5590) {
            for (int i = 0; i < 23; i++) {
                if (li_SecPosCode >= li_SecPosValue[i]
                        && li_SecPosCode < li_SecPosValue[i + 1]) {
                    chinese = lc_FirstLetter[i];
                    break;
                }
            }
        } else { // 非汉字字符,如图形符号或ASCII码
            chinese = this.conversionStr(chinese, "ISO8859-1", "GB2312");
            chinese = chinese.substring(0, 1);
        }
    }

    return chinese;
}

/**
 * 字符串编码转换
 * @param str 要转换编码的字符串
 * @param charsetName 原来的编码
 * @param toCharsetName 转换后的编码
 * @return 经过编码转换后的字符串
 */
private String conversionStr(String str, String charsetName,String toCharsetName) {
    try {
        str = new String(str.getBytes(charsetName), toCharsetName);
    } catch (UnsupportedEncodingException ex) {
        System.out.println("字符串编码转换异常：" + ex.getMessage());
    }
    return str;
}

private ArrayList<String> mItems;
Collections.sort(mItems, Collator.getInstance(java.util.Locale.CHINA)); // 排序

    //是否连接WIFI
    public static boolean isWifiConnected(Context context)
    {
        ConnectivityManager connectivityManager = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo wifiNetworkInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
        return wifiNetworkInfo.isConnected();
    }


    /**** 打开WIFI***/
    public static boolean openWifi(Context context){
        return opclWifi(context, true);
    }
   
    /**** 关闭WIFI***/
    public static boolean closeWifi(Context context){
        return opclWifi(context, false);
    }
   
    /**** 打开关闭WIFI****/
    private static boolean opclWifi(Context context, boolean type){
        boolean result = true;
        // 获取WIFIManager实例
        WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
   
        if (wifiManager.isWifiEnabled() ^ type) {
             // 打开关闭WIFI
             result = wifiManager.setWifiEnabled(type);
        }
   
        return result;
    }

加入权限：

    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

9、int数据转化成十六进制。二进制。八进制。无符号数字符串：

    public static void printInt(int i) {
    	System.out.println(Integer.toBinaryString(i));   // 二进制输出
    	System.out.println(Integer.toHexString(i));      // 十六进制输出
    	System.out.println(Integer.toOctalString(i));    // 八进制输出
    	System.out.println(Integer.toUnsignedString(i)); // 转化成无符号数输出
    	System.out.println(Integer.toString(i));         // 转化成String输出
    }

    	System.out.println("======== 输出正数 =========");
        int i = 100;
        printInt(i);
        System.out.println("======== 输出负 =========");
        i = -100;
        printInt(i);

======== 输出正数 =========
1100100
64
144
100
100
======== 输出负 =========
11111111111111111111111110011100
ffffff9c
37777777634
4294967196
-100