public class MainActivity extends Activity {
    private String str;
@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getTime();
getJudgetoDay();//判斷是否是今天
getJudgeYesterday();//判斷是否是昨天
}

    public void getJudgeYesterday
 
() {
        try {
            boolean flag = IsYesterday(str);
            if (flag == true) {//是昨天
                //TODO
} else {//不是昨天
                //TODO
}
        } catch (ParseException e) {
            e.printStackTrace();
}
    }

    public void getJudgetoDay() {
        try {
            boolean 
 
flag = IsToday(str);
            if (flag == true) {//是今天
                //TODO
} else {//不是今天
                //TODO
}
        } catch (ParseException e) {
            e.printStackTrace();
}
    }

    private void getTime() {
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"
 
);//得到當前的時間
Date curDate = new Date(System.currentTimeMillis());
str = formatter.format(curDate);
}

    /**
     * 判斷是否為今天(效率比較高)
     *
     * @param day 傳入的 時間  "2016-06-28 10:10:30" "2016-06-28" 都可以
     * @return true今天 false不是
     * @throws ParseException
     */
public static boolean IsToday(String day) throws ParseException {

        Calendar pre = Calendar.getInstance();
Date predate = new Date(System.currentTimeMillis());
pre.setTime(predate);
Calendar cal = Calendar.getInstance();
Date date = getDateFormat().parse(day);
cal.setTime(date);
        if (cal.get(Calendar.YEAR) == (pre.get(Calendar.YEAR))) {
            int diffDay = cal.get(Calendar.DAY_OF_YEAR)
                    - pre.get(Calendar.DAY_OF_YEAR);
            if (diffDay == 0) {
                return true;
}
        }
        return false;
}

    /**
     * 判斷是否為昨天(效率比較高)
     *
     * @param day 傳入的 時間  "2016-06-28 10:10:30" "2016-06-28" 都可以
     * @return true今天 false不是
     * @throws ParseException
     */
public static boolean IsYesterday(String day) throws ParseException {

        Calendar pre = Calendar.getInstance();
Date predate = new Date(System.currentTimeMillis());
pre.setTime(predate);
Calendar cal = Calendar.getInstance();
Date date = getDateFormat().parse(day);
cal.setTime(date);
        if (cal.get(Calendar.YEAR) == (pre.get(Calendar.YEAR))) {
            int diffDay = cal.get(Calendar.DAY_OF_YEAR)
                    - pre.get(Calendar.DAY_OF_YEAR);
            if (diffDay == -1) {
                return true;
}
        }
        return false;
}

    public static SimpleDateFormat getDateFormat() {
        if (null == DateLocal.get()) {
            DateLocal.set(new SimpleDateFormat("yyyy-MM-dd", Locale.CHINA));
}
        return DateLocal.get();
}


    private static ThreadLocal<SimpleDateFormat> DateLocal = new ThreadLocal<SimpleDateFormat>();
}