Android 识别时间是昨天，今天

在项目开发中经常会用到时间，对时间的操作最常见的就是识别出是哪一天，是今天，还是昨天，甚至是星期几！

我这里有一篇工具类，提供给大家，希望能给大家带来帮助！！

package com.dash.a09_alipay;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;

/**
 * Created by zzt on 2018/5/2.
 */

public class DataUtils {
    /**
     * 判断给定字符串时间是否为今日(效率不是很高，不过也是一种方法)
     * @param sdate
     * @return boolean
     */
    public static boolean isToday(String sdate){
        boolean b = false;
        Date time = toDate(sdate);
        Date today = new Date();
        if(time != null){
            String nowDate = dateFormater2.get().format(today);
            String timeDate = dateFormater2.get().format(time);
            if(nowDate.equals(timeDate)){
                b = true;
            }
        }
        return b;
    }

    /**
     * 将字符串转位日期类型
     * @param sdate
     * @return
     */
    public static Date toDate(String sdate) {
        try {
            return dateFormater.get().parse(sdate);
        } catch (Exception e) {
            return null;
        }
    }

    private final static ThreadLocal<SimpleDateFormat> dateFormater = new ThreadLocal<SimpleDateFormat>() {
        @Override
        protected SimpleDateFormat initialValue() {
            return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        }
    };

    private final static ThreadLocal<SimpleDateFormat> dateFormater2 = new ThreadLocal<SimpleDateFormat>() {
        @Override
        protected SimpleDateFormat initialValue() {
            return new SimpleDateFormat("yyyy-MM-dd");
        }
    };
    private static ThreadLocal<SimpleDateFormat> DateLocal = new ThreadLocal<SimpleDateFormat>();

    /**
     * 判断是否为今天(效率比较高)
     * @param day 传入的 时间  "2016-06-28 10:10:30" "2016-06-28" 都可以
     * @return true今天 false不是
     * @throws Exception
     */
    public static boolean IsToday(String day)  {

        Calendar pre = Calendar.getInstance();
        Date predate = new Date(System.currentTimeMillis());
        pre.setTime(predate);

        Calendar cal = Calendar.getInstance();
        Date date = null;
        try {
            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;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return false;
    }

    /**
     * 判断是否为昨天(效率比较高)
     * @param day 传入的 时间  "2016-06-28 10:10:30" "2016-06-28" 都可以
     * @return true今天 false不是
     * @throws Exception
     */
    public static boolean IsYesterday(String day)  {

        Calendar pre = Calendar.getInstance();
        Date predate = new Date(System.currentTimeMillis());
        pre.setTime(predate);

        Calendar cal = Calendar.getInstance();
        Date date = null;
        try {
            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;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return false;
    }

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

以上就是识别时间的工具类，这个工具类中只是做了识别是昨天还是今天！！如果有更全面，希望可以留言，分享！共同进步嘛！！

一下是我再Activity中的运用：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    timetext = (TextView) findViewById(R.id.time);

    Date date = new Date(System.currentTimeMillis());
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    String format = simpleDateFormat.format(date);

    format="2018-04-01 15:23:20";
    if(DataUtils.isToday(format)){
        Date date1 = DataUtils.toDate(format);
        SimpleDateFormat simpleDateFormat1 = new SimpleDateFormat("HH:mm:ss");
        String format1 = simpleDateFormat1.format(date1);
        timetext.setText(format1);

    }else{
        if(DataUtils.IsYesterday(format)){
            timetext.setText("昨天");
        }else{
            timetext.setText(format);
        }
    }
}

效果图，这里就不展示了，太简单了，没意思！！