android.text.format.DateFormat "HH" 不像 java.text.SimpleDateFormat 那样被识别
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android.text.format.DateFormat "HH" is not recognized like with java.text.SimpleDateFormat
提问by Alejandro Colorado
When I use the "HH" flag in android.text.format.DateFormat, it is interpreted as a literal "HH". But when I use java.text.SimpleDateFormatit is interpreted as the 2 digit Hour. Why are they different?
当我在 中使用“HH”标志时android.text.format.DateFormat，它被解释为文字“HH”。但是当我使用java.text.SimpleDateFormat它时，它被解释为 2 位小时。他们为什么不同？
I'm not looking for a working alternative (I already know I have to use kkinstead of HH). I'm just curious why "HH" isn't recognized.
我不是在寻找可行的替代方案（我已经知道我必须使用kk代替HH）。我只是好奇为什么“HH”不被识别。
Java example:
Java示例：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Calendar calendar = Calendar.getInstance();
String dateJava = new java.text.SimpleDateFormat(
"dd-MM-yyyy HH:mm:ss").format(calendar.getTime());
String dateAndroid = android.text.format.DateFormat.format(
"dd-MM-yyyy HH:mm:ss", calendar).toString();
TextView tvAndroid = (TextView) findViewById(R.id.tvAndroid);
TextView tvJava = (TextView) findViewById(R.id.tvJava);
tvAndroid.setText("Android: " + dateAndroid); //prints 26-05-2013 HH:36:34
tvJava.setText("Java: " + dateJava); //prints 26-05-2013 22:36:34
}
Output is:
输出是：
Android: 26-05-2013 HH:36:34
Java: 26-05-2013 22:36:34
I expect both to be 26-05-2013 22:36:34
我希望两者都是 26-05-2013 22:36:34
Does Android's DateFormat have a bug?
Android 的 DateFormat 有错误吗？
Java's SimpleDateFormat accepts these:
Java 的 SimpleDateFormat 接受这些：
H Hour in day (0-23) Number 0
k Hour in day (1-24) Number 24
K Hour in am/pm (0-11) Number 0
h Hour in am/pm (1-12) Number 12
So it appears the Android developers decided to change the meaning of kand in their DateFormat function it is equivalent to the SimpleDateFormat Has they explicitly say in their documentation page:
因此，Android 开发人员似乎决定更改kDateFormat 函数的含义，它等同于 SimpleDateFormat，H正如他们在文档页面中明确指出的那样：
This constant was deprecated in API level 18. Use a literal 'H' (for
compatibility with SimpleDateFormat and Unicode) or 'k' (for compatibility
with Android releases up to and including Jelly Bean MR-1) instead. Note
that the two are incompatible.
What is the reason for this?
这是什么原因？
采纳答案by Squonk
I understand you have accepted an answer already but just to explain this fully to you...
我知道您已经接受了一个答案，但只是为了向您充分解释这一点......
From the source code for DateFormat.java...
从DateFormat.java的源代码...
The
formatmethods in this class implement a subset of Unicode UTS #35patterns. The subset currently supported by this class includes the following format characters:acdEHhLKkLMmsyz. Up to API level 17, onlyadEhkMmszywere supported. Note that this class incorrectly implementskas if it wereHfor backwards compatibility.
format此类中的方法实现了 Unicode UTS #35模式的子集 。此类当前支持的子集包括以下格式字符：acdEHhLKkLMmsyz. 仅adEhkMmszy支持API 级别 17 。请注意，这个类错误地实现k，好像它是H为了向后兼容。
Note the part I have marked in bold.
请注意我用粗体标记的部分。
The source I linked to has been updated to allow the use of H but it isn't on general release yet (API 17 is the current release of Android and doesn't support H).
我链接到的源已更新以允许使用 H，但它还没有正式发布（API 17 是 Android 的当前版本，不支持 H）。
Later in the source, at the stage of declaring the format character constants, there is this comment...
后来在源码中，在声明格式字符常量的阶段，有这样的注释……
/**
* @deprecated Use a literal {@code 'H'} (for compatibility with {@link SimpleDateFormat}
* and Unicode) or {@code 'k'} (for compatibility with Android releases up to and including
* Jelly Bean MR-1) instead. Note that the two are incompatible.
*/
@Deprecated
public static final char HOUR_OF_DAY = 'k';
...and later during character replacement...
......后来在字符替换过程中......
case 'H': // hour in day (0-23)
case 'k': // hour in day (1-24) [but see note below]
{
int hour = inDate.get(Calendar.HOUR_OF_DAY);
// Historically on Android 'k' was interpreted as 'H', which wasn't
// implemented, so pretty much all callers that want to format 24-hour
// times are abusing 'k'. http://b/8359981.
if (false && c == 'k' && hour == 0) {
hour = 24;
}
replacement = zeroPad(hour, count);
}
break;
回答by Brian Roach
Because ... it's not the same thing and it's behaving as the documentation states?
因为......它不是一回事，它的行为与文档说明的一样？
From the Documentation for android.text.format.DateFormat
来自android.text.format.DateFormat的文档
This class only supports a subset of the full Unicode specification. Use SimpleDateFormat if you need more.
此类仅支持完整 Unicode 规范的一个子集。如果您需要更多，请使用 SimpleDateFormat。
But if you read the docs further:
但是，如果您进一步阅读文档：
public static final char HOUR_OF_DAY
This designator indicates the hour of the day in 24 hour format. Example for 3pm: k -> 15 Examples for midnight: k -> 0 kk -> 00
公共静态最终字符 HOUR_OF_DAY
此指示符以 24 小时格式指示一天中的小时。下午 3 点的示例：k -> 15 午夜的示例：k -> 0 kk -> 00
So ... using that class, it'd be kkinstead of HH
所以......使用那个类，它会kk代替HH
回答by msh
For android.text.format.DateFormat you designate Hour in day as kklike this:
对于 android.text.format.DateFormat，您可以kk像这样指定一天中的小时：
String dateAndroid = android.text.format.DateFormat.format(
"dd-MM-yyyy kk:mm:ss", calendar).toString();
For java.text.SimpleDateFormat you designate hour in day as HH.
对于 java.text.SimpleDateFormat，您将一天中的小时指定为HH.
H hour in day (0-23)
一天中的 H 小时 (0-23)
Documentation for android.text.format.DateFormat:
android.text.format.DateFormat 的文档：
public static final char HOUR_OF_DAY
This designator indicates the hour of the day in 24 hour format. Example for 3pm: k -> 15 Examples for midnight: k -> 0 kk -> 00
公共静态最终字符 HOUR_OF_DAY
此指示符以 24 小时格式指示一天中的小时。下午 3 点的示例：k -> 15 午夜的示例：k -> 0 kk -> 00
回答by AlexR
I have never programmed for Android. I googled the DateFormat javadocand saw there the following examples:
我从来没有为Android编程。我用谷歌搜索了DateFormat javadoc并在那里看到了以下示例：
Examples for April 6, 1970 at 3:23am:
"MM/dd/yy h:mmaa" -> "04/06/70 3:23am"
"MMM dd, yyyy h:mmaa" -> "Apr 6, 1970 3:23am"
"MMMM dd, yyyy h:mmaa" -> "April 6, 1970 3:23am"
"E, MMMM dd, yyyy h:mmaa" -> "Mon, April 6, 1970 3:23am&
"EEEE, MMMM dd, yyyy h:mmaa" -> "Monday, April 6, 1970 3:23am"
"'Noteworthy day: 'M/d/yy" -> "Noteworthy day: 4/6/70"
The "hour" is marked using small letter hin opposite to SimpleDateFormatwhere capital letter is used for this purpose.
“小时”用小写字母标记h，与SimpleDateFormat用于此目的的大写字母相反。
回答by Alex
This work for all Android 4.0+ and for two date time format.
这适用于所有 Android 4.0+ 和两种日期时间格式。
Use java.text.SimpleDateFormat.
使用 java.text.SimpleDateFormat。
Work example:
工作示例：
24 hour format use this date pattern = "dd-MM-yyyy HH:mm";
24 小时格式使用此日期模式 = " dd-MM-yyyy HH:mm";
12 hour format use this date pattern = "dd-MM-yyyy hh:mm a";
12 小时格式使用此日期模式 = " dd-MM-yyyy hh:mm a";
public static String getDateAsString(Date date, String pattern) {
Locale locale = new Locale("EN");
SimpleDateFormat sdf = null;
try {
sdf = new SimpleDateFormat(pattern, locale);
return sdf.format(date);
} catch (IllegalArgumentException ex) {
// default format
sdf = new SimpleDateFormat("dd-MM-yyyy HH:mm", locale);
return sdf.format(date);
}
}
