Android 在 7 天（一周）之前获取日期

Question

How to get date before one week from now in android in this format:

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

ex: now 2010-09-19 HH:mm:ss , before one week 2010-09-12 HH:mm:ss

Thanks

Answer 1

Parse the date:

Date myDate = dateFormat.parse(dateString);

And then either figure out how many milliseconds you need to subtract:

Date newDate = new Date(myDate.getTime() - 604800000L); // 7 * 24 * 60 * 60 * 1000

Or use the API provided by the java.util.Calendar class:

Calendar calendar = Calendar.getInstance();
calendar.setTime(myDate);
calendar.add(Calendar.DAY_OF_YEAR, -7);
Date newDate = calendar.getTime();

Then, if you need to, convert it back to a String:

String date = dateFormat.format(newDate);

Answer 2

I have created my own function that may helpful to get Next/Previous date from

Current Date:

/**
 * Pass your date format and no of days for minus from current 
 * If you want to get previous date then pass days with minus sign
 * else you can pass as it is for next date
 * @param dateFormat
 * @param days
 * @return Calculated Date
 */
public static String getCalculatedDate(String dateFormat, int days) {
    Calendar cal = Calendar.getInstance();
    SimpleDateFormat s = new SimpleDateFormat(dateFormat);
    cal.add(Calendar.DAY_OF_YEAR, days);
    return s.format(new Date(cal.getTimeInMillis()));
}

Example:

getCalculatedDate("dd-MM-yyyy", -10); // It will gives you date before 10 days from current date

getCalculatedDate("dd-MM-yyyy", 10);  // It will gives you date after 10 days from current date

and if you want to get Calculated Date with passing Your own date:

public static String getCalculatedDate(String date, String dateFormat, int days) {
    Calendar cal = Calendar.getInstance();
    SimpleDateFormat s = new SimpleDateFormat(dateFormat);
    cal.add(Calendar.DAY_OF_YEAR, days);
    try {
        return s.format(new Date(s.parse(date).getTime()));
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        Log.e("TAG", "Error in Parsing Date : " + e.getMessage());
    }
    return null;
}

Example with Passing own date:

getCalculatedDate("01-01-2015", "dd-MM-yyyy", -10); // It will gives you date before 10 days from given date

getCalculatedDate("01-01-2015", "dd-MM-yyyy", 10);  // It will gives you date after 10 days from given date

Answer 3

tl;dr

LocalDate
    .now( ZoneId.of( "Pacific/Auckland" ) )           // Get the date-only value for the current moment in a specified time zone.
    .minusWeeks( 1 )                                  // Go back in time one week.
    .atStartOfDay( ZoneId.of( "Pacific/Auckland" ) )  // Determine the first moment of the day for that date in the specified time zone.
    .format( DateTimeFormatter.ISO_LOCAL_DATE_TIME )  // Generate a string in standard ISO 8601 format.
    .replace( "T" , " " )                             // Replace the standard "T" separating date portion from time-of-day portion with a SPACE character.

java.time

The modern approach uses the java.time classes.

The LocalDate class represents a date-only value without time-of-day and without time zone.

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec .

Specify a proper time zone name in the format of continent/region , such as America/Montreal , Africa/Casablanca , or Pacific/Auckland . Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.forID( "America/Montreal" ) ;
LocalDate now = LocalDate.now ( z ) ;

Do some math using the minus… and plus… methods.

LocalDate weekAgo = now.minusWeeks( 1 );

Let java.time determine the first moment of the day for your desired time zone. Do not assume the day starts at 00:00:00 . Anomalies such as Daylight Saving Time means the day may start at another time-of-day such as 01:00:00 .

ZonedDateTime weekAgoStart = weekAgo.atStartOfDay( z ) ;

Generate a string representing this ZonedDateTime object using a DateTimeFormatter object. Search Stack Overflow for many more discussions on this class.

DateTimeFormatter f = DateTimeFormatter.ISO_LOCAL_DATE_TIME ;
String output = weekAgoStart.format( f ) ;

That standard format is close to what you want, but has a T in the middle where you want a SPACE. So substitute SPACE for T .

output = output.replace( "T" , " " ) ;

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date , Calendar , & SimpleDateFormat .

The Joda-Time project, now in maintenance mode , advises migration to the java.time classes.

To learn more, see the Oracle Tutorial . And search Stack Overflow for many examples and explanations. Specification is JSR 310 .

Where to obtain the java.time classes?

• Java SE 8 , Java SE 9 , and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport .
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP… .

Joda-Time

Update: The Joda-Time project is now in maintenance mode. The team advises migration to the java.time classes.

Using the Joda-Time library makes date-time work much easier.

Note the use of a time zone. If omitted, you are working in UTC or the JVM's current default time zone.

DateTime now = DateTime.now ( DateTimeZone.forID( "America/Montreal" ) ) ;
DateTime weekAgo = now.minusWeeks( 1 );
DateTime weekAgoStart = weekAgo.withTimeAtStartOfDay();

Answer 4

Try this

One single method for getting the date from current or bypassing any date

@Pratik Butani's second method for getting the date from our own date is not working at my end.

Kotlin

fun getCalculatedDate(date: String, dateFormat: String, days: Int): String {
    val cal = Calendar.getInstance()
    val s = SimpleDateFormat(dateFormat)
    if (date.isNotEmpty()) {
        cal.time = s.parse(date)
    }
    cal.add(Calendar.DAY_OF_YEAR, days)
    return s.format(Date(cal.timeInMillis))
}

Java

 public static String getCalculatedDate(String date,String dateFormat, int days) {
    Calendar cal = Calendar.getInstance();
    SimpleDateFormat s = new SimpleDateFormat(dateFormat);
    if (!date.isEmpty()) {
        try {
            cal.setTime(s.parse(date));
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
    cal.add(Calendar.DAY_OF_YEAR, days);
    return s.format(new Date(cal.getTimeInMillis()));
}

Usage

1. getCalculatedDate("", "yyyy-MM-dd", -2) // If you want date from today
2. getCalculatedDate("2019-11-05", "yyyy-MM-dd", -2) // If you want date from your own

Answer 5

I can see two ways:

1. Use aGregorianCalendar :

    Calendar someDate = GregorianCalendar.getInstance(); someDate.add(Calendar.DAY_OF_YEAR, -7); SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String formattedDate = dateFormat.format(someDate);

2. Use a android.text.format.Time :

    long yourDateMillis = System.currentTimeMillis() - (7 * 24 * 60 * 60 * 1000); Time yourDate = new Time(); yourDate.set(yourDateMillis); String formattedDate = yourDate.format("%Y-%m-%d %H:%M:%S");

Solution 1 is the "official" java way, but using a GregorianCalendar can have serious performance issues so Android engineers have added the android.text.format.Time object to fix this.

Answer 6

public static Date getDateWithOffset(int offset, Date date){
    Calendar calendar = calendar = Calendar.getInstance();;
    calendar.setTime(date);
    calendar.add(Calendar.DAY_OF_MONTH, offset);
    return calendar.getTime();
}

Date weekAgoDate = getDateWithOffset(-7, new Date());

---

OR using Joda:

add Joda library

    implementation 'joda-time:joda-time:2.10'

'

DateTime now = new DateTime();
DateTime weekAgo = now.minusWeeks(1);
Date weekAgoDate = weekAgo.toDate()// if you want to convert it to Date

-----------------------------UPDATE-------------------------------

Use Java 8 APIs or ThreeTenABP for Android (minSdk<24).

ThreeTenABP:

implementation 'com.jakewharton.threetenabp:threetenabp:1.2.1'

'

LocalDate now= LocalDate.now();
now.minusWeeks(1);

Answer 7

You can use this code for get exact string which you want.

object DateUtil{
    fun timeAgo(context: Context, time_ago: Long): String {
        val curTime = Calendar.getInstance().timeInMillis / 1000
        val timeElapsed = curTime - (time_ago / 1000)
        val minutes = (timeElapsed / 60).toFloat().roundToInt()
        val hours = (timeElapsed / 3600).toFloat().roundToInt()
        val days = (timeElapsed / 86400).toFloat().roundToInt()
        val weeks = (timeElapsed / 604800).toFloat().roundToInt()
        val months = (timeElapsed / 2600640).toFloat().roundToInt()
        val years = (timeElapsed / 31207680).toFloat().roundToInt()

        // Seconds
        return when {
            timeElapsed <= 60 -> context.getString(R.string.just_now)
            minutes <= 60 -> when (minutes) {
                1 -> context.getString(R.string.x_minute_ago, minutes)
                else -> context.getString(R.string.x_minute_ago, minutes)
            }
            hours <= 24 -> when (hours) {
                1 -> context.getString(R.string.x_hour_ago, hours)
                else -> context.getString(R.string.x_hours_ago, hours)
            }
            days <= 7 -> when (days) {
                1 -> context.getString(R.string.yesterday)
                else -> context.getString(R.string.x_days_ago, days)
            }
            weeks <= 4.3 -> when (weeks) {
                1 -> context.getString(R.string.x_week_ago, weeks)
                else -> context.getString(R.string.x_weeks_ago, weeks)
            }
            months <= 12 -> when (months) {
                1 -> context.getString(R.string.x_month_ago, months)
                else -> context.getString(R.string.x_months_ago, months)
            }
            else -> when (years) {
                1 -> context.getString(R.string.x_year_ago, years)
                else -> context.getString(R.string.x_years_ago, years)
            }
        }
    }

}

Answer 8

Kotlin:

import java.util.*

val Int.week: Period
    get() = Period(period = Calendar.WEEK_OF_MONTH, value = this)

internal val calendar: Calendar by lazy {
    Calendar.getInstance()
}

operator fun Date.minus(duration: Period): Date {
    calendar.time = this
    calendar.add(duration.period, -duration.value)
    return calendar.time
}

data class Period(val period: Int, val value: Int)

Usage:

val newDate = oldDate - 1.week
// Or val newDate = oldDate.minus(1.week)