从JAR中保存首选项 [英] Saving Preferences from within a JAR
问题描述
我目前正在编写游戏，并且已经到了我需要用户能够保存诸如JFrame大小，键绑定等内容的首选项的位置。用户将通过下载的jar运行游戏来自我的网站。
I am currently writing a game, and have come to the point where I need the user to be able to save preferences for things such as the JFrame size, key bindings etc. The users will be running the game through a jar downloaded from my website.
我决定使用java.util.prefs.Preferences下的Preferences API。在阅读文档等内容时，我仍然很新，并且希望有人帮我解释一下。
I've decided to go with the Preferences API under "java.util.prefs.Preferences". I am still quite new when it comes to reading things like documentation, and would like someone to help explain a bit to me.
到目前为止，我有这样的事情：
So far, I have something like this:
Preferences prefs = Preferences.userNodeForPackage(com.custardgames.horde2d.Game.class);
prefs.put(name, value);
现在，我如何实际保存用户计算机上的首选项文件？现在，如果我再次运行该程序并尝试：
Now then, how do I actually get to saving the preference file on the users computer? Right now, if I run the program again and try just:
Preferences prefs = Preferences.userNodeForPackage(com.custardgames.horde2d.Game.class);
System.out.println(prefs.get(name, null));
它只返回null，如果没有保存的话，这是默认值。我知道我错过了实际保存文件的重要部分，然后以正确的方式打开它，但谷歌搜索没有得到太多。
It just returns null which is the default value if there is nothing saved. I know I am missing the vital part of actually saving the file, and then opening it the correct way, but haven't gotten much out of googling it.
非常感谢提前！
编辑：
仅供参考，为了阅读图像，我是使用类似这样的东西：
FYI, for reading images, I am using something like this:
BufferedImage currentImage=ImageIO.read(this.getClass().getClassLoader().getResource("res/images/image.jpg"));
我希望能够做一些与偏好类似的事情。
I would like to be able to do something similar with preferences.
编辑：
name 和 value 都是事先声明的String变量。
name and value are both String variables declared beforehand.
推荐答案
您确定 name 变量具有相同的值吗？因为它应该返回正确的存储值 - 也许值为空？
Are you sure that name variable has the same value? Because it should return correct stored value - maybe value is null?
尝试在存储之前将它们打印出来&获得。
Try printing them out just before storing & getting.
您还可以尝试在存储后刷新首选项：
You can also try to flush preferences after storing:
prefs.flush();
如果你在Windows上，你可以检查首选项是否存储在 regedit
If you're on Windows you can check if the preferences are stored in regedit under
\HKEY_CURRENT_USER\Software\JavaSoft\Prefs\<your package path>
我不确定但是你的主目录中应该有一个隐藏文件夹。类似
in Linux I'm not sure but there should be a hidden folder in your home directory. Something like
~/.java/.prefs/<package path>
我开发了一个JFrame，使用首选项存储最后一个位置&框架的大小。您可以在这里查看：
I've developed a JFrame using preferences for storing last position & size of a frame. You can look at it here:
图书馆位于：
java-utils
您可能感兴趣的代码：
public void saveSize() {
Preferences preferences = Preferences.userNodeForPackage(this.getClass());
preferences.put(getId() + X_KEY, String.valueOf(getLocation().x));
preferences.put(getId() + Y_KEY, String.valueOf(getLocation().y));
preferences.put(getId() + W_KEY, String.valueOf(getSize().width));
preferences.put(getId() + H_KEY, String.valueOf(getSize().height));
preferences.put(getId() + MAX_KEY,
String.valueOf((getExtendedState() & JFrame.MAXIMIZED_BOTH) == JFrame.MAXIMIZED_BOTH));
try {
preferences.flush();
}
catch(BackingStoreException e) {
e.printStackTrace();
}
}
public void setSavedSize() {
Preferences preferences = Preferences.userNodeForPackage(this.getClass());
String xs = preferences.get(getId() + X_KEY, "");
String ys = preferences.get(getId() + Y_KEY, "");
String ws = preferences.get(getId() + W_KEY, "");
String hs = preferences.get(getId() + H_KEY, "");
String max = preferences.get(getId() + MAX_KEY, "");
if(max != null && !max.trim().isEmpty() && Boolean.valueOf(max) == true) {
setDefaultSize();
setExtendedState(JFrame.MAXIMIZED_BOTH);
return;
}
if(xs.length() == 0 || ys.length() == 0 || ws.length() == 0 || hs.length() == 0) {
setDefaultSize();
}
else {
sizeFromPreferences = true;
int x = Integer.parseInt(xs);
int y = Integer.parseInt(ys);
int w = Integer.parseInt(ws);
int h = Integer.parseInt(hs);
setLocation(x, y);
setSize(w, h);
}
}
编辑
如果要创建某种设置存储系统，可以使用与 RememberableFrame 中相同的约定 - 使用前缀。
If you want to create some kind of settings storing system you can use the same convention as in RememberableFrame - use prefixes.
在 RememberableFrame 我使用：
private String getId() {
return this.getClass().getSimpleName() + id;
}
其中 id 是开发人员提供的自定义字符串或空字符串。但请记住，您要设置的属性的密钥有长度限制。
where id is custom String provided by the developer or an empty string. But remember that the key of the property you want to set has length limit.
来自API：
static int MAX_KEY_LENGTH
Maximum length of string allowed as a key (80 characters).
static int MAX_NAME_LENGTH
Maximum length of a node name (80 characters).
static int MAX_VALUE_LENGTH
Maximum length of string allowed as a value (8192 characters).
您可能还会考虑专门用于存储设置目的。例如，类 KeyboardSettings ，甚至在不同的包中。
You might also consider using classes specifically for "storing settings" purposes. For example class KeyboardSettings and even in different packages.
这篇关于从JAR中保存首选项的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
