如何实现以前/下个月按钮和显示日期当月？(How do I implement previous/n

场景：

我有示出的费用清单与所述类别和金额和日期沿着费用追踪iOS应用与我从费用明细视图控制器到一个表视图（与读取的结果控制器）存储费用。我有我的实体“钱”，这是任何费用或收入父实体日期属性。

题：

我想要的是基本分类按月我的费用，并显示其为分节标题标题，例如：（11月1日日 - 11月30,2012），它显示的费用金额，并按照特定的月份相关的东西。在该视图中提供了两个按钮，如果我会按右边的按钮，它会通过一个月（12月1日至十二月31日，2012）增加的月份，同样左键将通过每月递减一个月。

我将如何实现这一目标？我想下面的代码 - 这是有点儿工作。假设我有我的当前节头部为（Nov1 - 二〇一二年十一月三十〇日），当我按下左键，它给我的节头（10月1日至10月30日，2012）这是不对的，应该是2012年10月31日而不是2012年10月30日。

- (NSDate *)firstDateOfTheMonth
{
    self.startDate = [NSDate date];

    NSCalendar* calendar = [NSCalendar currentCalendar];

    [calendar setTimeZone:[NSTimeZone localTimeZone]];

    NSDateComponents* components = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:self.startDate];

    [components setDay:1];

    firstDateOfTheMonth = [[calendar dateFromComponents:components] retain];

    return firstDateOfTheMonth;

}

- (NSDate *)lastDateOfTheMonth
{
    NSCalendar* calendar = [NSCalendar currentCalendar];

    [calendar setTimeZone:[NSTimeZone localTimeZone]];

    NSDateComponents* components = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:firstDateOfTheMonth];

    [components setMonth:[components month]+1];
    [components setDay:0];

    lastDateOfTheMonth = [[calendar dateFromComponents:components] retain];

    return lastDateOfTheMonth;
}

然后，我有一个名为“monthCalculation”在我称之为上述两种方法的方法。

- (void)monthCalculation
{
    [self firstDateOfTheMonth];
    [self lastDateOfTheMonth];
}

现在下面的代码时，我按下左键（递减由一个月月）：

- (IBAction)showPreviousDates:(id)sender
{
    [self monthCalculation];

    NSDateComponents *dateComponents = [[[NSDateComponents alloc] init] autorelease];
    [dateComponents setMonth:-1];

    NSDate *newDate1 = [[NSCalendar currentCalendar]
                        dateByAddingComponents:dateComponents
                        toDate:firstDateOfTheMonth options:0];

    NSDate *newDate2 = [[NSCalendar currentCalendar]
                        dateByAddingComponents:dateComponents
                        toDate:lastDateOfTheMonth options:0];

    self.startDate = newDate1;
    self.endDate = newDate2;

    NSLog(@" self start date in previous mode =%@", self.startDate);
    NSLog(@" self end date in previous mode =%@", self.endDate);
}

下面的代码时，我按右边的按钮（递增由一个月月）：

- (IBAction)showNextDates:(id)sender
{
    [self monthCalculation];

    NSDateComponents *dateComponents = [[[NSDateComponents alloc] init] autorelease];
    [dateComponents setMonth:1];

    NSDate *newDate1 = [[NSCalendar currentCalendar]
                        dateByAddingComponents:dateComponents
                        toDate:firstDateOfTheMonth options:0];

    NSDate *newDate2 = [[NSCalendar currentCalendar]
                        dateByAddingComponents:dateComponents
                        toDate:lastDateOfTheMonth options:0];

    self.startDate = newDate1;
    self.endDate = newDate2;

    NSLog(@" self start date in previous mode =%@", self.startDate);
    NSLog(@" self end date in previous mode =%@", self.endDate);
}

我这样做对吗？或者有更好的方法来做到实现这一目标？任何帮助将不胜感激。

Answer 1:

这里有一些方法应该做你想要什么：

首先，在您的viewDidLoad方法中添加：

self.startDate = [NSDate date];
[self updateDateRange];

这给你一个起点。然后，我添加了以下五种方法（注： previousMonthButtonPressed / nextMonthButtonPressed应连接到你的按钮）：

// Return the first day of the month for the month that 'date' falls in:
- (NSDate *)firstDayOfMonthForDate:(NSDate *)date
{
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:date];
    comps.day               = 1;
    return [cal dateFromComponents:comps];
}

// Return the last day of the month for the month that 'date' falls in:
- (NSDate *)lastDayOfMonthForDate:(NSDate *)date
{
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:date];
    comps.month             += 1;
    comps.day               = 0;
    return [cal dateFromComponents:comps];
}

// Move the start date back one month
- (IBAction)previousMonthButtonPressed:(id)sender {
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:self.startDate];
    comps.month             -= 1;
    self.startDate          = [cal dateFromComponents:comps];
    [self updateDateRange];
}

// Move the start date forward one month
- (IBAction)nextMonthButtonPressed:(id)sender {
    NSCalendar *cal         = [NSCalendar currentCalendar];
    NSDateComponents *comps = [cal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
                                     fromDate:self.startDate];
    comps.month             += 1;
    self.startDate          = [cal dateFromComponents:comps];
    [self updateDateRange];
}

// Print the new range of dates.
- (void)updateDateRange
{
    NSLog(@"First day of month: %@", [self firstDayOfMonthForDate:self.startDate]);
    NSLog(@"Last day of month: %@",  [self lastDayOfMonthForDate:self.startDate]);
}

Answer 2:

试试这个：

- (NSDate *)lastDateOfTheMonth
{
    NSCalendar* calendar = [NSCalendar currentCalendar];
    [calendar setTimeZone:[NSTimeZone localTimeZone]];

    NSDateComponents* components = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:firstDateOfTheMonth];
    [components setMonth:[components month]+1];

    NSDateComponents* offset = [[[NSDateComponents alloc] init] retain];
    [offset setDay:-1];

    lastDateOfTheMonth = [[calendar dateByAddingComponents:offset toDate:[components date] options:0] retain];
    return lastDateOfTheMonth;
}

文章来源: How do I implement previous/next month buttons and show dates for current month?