blocks|key|1088159|text|我不认为500kb会是一个大问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1088160|您所描述的正是我如何解决在活动中丢失数据的问题。我在Application类中创建了一个全局单例，并且能够从我使用的活动中访问它。|1088161|如果要大量使用数据，则可以在全局单例中传递数据。|1088162|public+class+YourApplication+extends+Application+
{+++++
+++++public+SomeDataClass+data+=+new+SomeDataClass();
}|code-block|syntax|javascript|1088163|然后在任何活动中通过以下方式调用它：|1088164|YourApplication+appState+=+((YourApplication)this.getApplication());
appState.data.UseAGetterOrSetterHere();+//+Do+whatever+you+need+to+with+the+data+here.|1088165|我在“全局单例”一节中对其进行here+in+my+blog+post讨论。|offset|length|1088166|entityMap|0|LINK|mutability|MUTABLE|url|https://web.archive.org/web/20130818035631/http://www.bryandenny.com/index.php/2010/05/25/what-i-learned-from-writing-my-first-android-application^0|0|0|0|0|0|0|F|K|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|15|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|9|@$Q|17|R|18|1|19]]|A|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

I don't think 500kb will be that big of a deal.

What you described is exactly how I tackled my problem of losing data in an activity. I created a global singleton in the Application class and was able to access it from the activities I used.

You can pass data around in a Global Singleton if it is going to be used a lot.

<pre><code>public class YourApplication extends Application 
{ 
 public SomeDataClass data = new SomeDataClass();
}
</code></pre>

Then call it in any activity by:

<pre><code>YourApplication appState = ((YourApplication)this.getApplication());
appState.data.UseAGetterOrSetterHere(); // Do whatever you need to with the data here.
</code></pre>

I discuss it <a href="https://web.archive.org/web/20130818035631/http://www.bryandenny.com/index.php/2010/05/25/what-i-learned-from-writing-my-first-android-application" rel="noreferrer">here in my blog post</a>, under the section "Global Singleton."

blocks|key|873497|text|实际上，您可以覆盖方向功能，以确保您的活动不会被销毁和重新创建。看，here。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|873498|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/456211/activity-restart-on-rotation-android^0|Y|4|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

You can actually override the orientation functionality to make sure that your activity isn't destroyed and recreated. Look <a href="https://stackoverflow.com/questions/456211/activity-restart-on-rotation-android">here</a>.

blocks|key|1088253|text|如果您想在活动之外访问“全局单例”，并且不想通过所有涉及的对象传递Context来获得单例，那么您可以只在应用程序类中定义一个静态属性，该属性保存对自身的引用。只需在onCreate()方法中初始化属性即可。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1088254|例如：|1088255|public+class+ApplicationController+extends+Application+{
++++private+static+ApplicationController+_appCtrl;

++++public+static+ApplicationController+getAppCtrl()
++++{
+++++++++return+_appCtrl;
++++}
}|code-block|syntax|javascript|1088256|因为Application的子类也可以获取资源，所以您可以在定义静态方法时简单地访问它们，该静态方法返回它们，如下所示：|1088257|public+static+Resources+getAppResources()
{
++++return+_appCtrl.getResources();
}|1088258|但是在传递对avoid+memory+leaks的上下文引用时要非常小心。|1088259|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/resources/articles/avoiding-memory-leaks.html^0|X|7|2B|A|0|0|0|2|B|0|0|6|I|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|15|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|16|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|17|8|@$9|18|A|19|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1B|8|@]|D|@$9|1C|A|1D|1|1E]]|E|$]]|$1|S|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

If you want to access the "Global Singleton" outside of an activity and you don't want to pass the <code>Context</code> through all the involved objects to obtain the singleton, you can just define a static attribute in your application class, which holds the reference to itself. Just initialize the attribute in the <code>onCreate()</code> method.

For example:

<pre><code>public class ApplicationController extends Application {
 private static ApplicationController _appCtrl;

 public static ApplicationController getAppCtrl()
 {
 return _appCtrl;
 }
}
</code></pre>

Because subclasses of <code>Application</code> also can obtain the Resources, you could access them simply when you define a static method, which returns them, like:

<pre><code>public static Resources getAppResources()
{
 return _appCtrl.getResources();
}
</code></pre>

But be very careful when passing around Context references to <a href="http://developer.android.com/resources/articles/avoiding-memory-leaks.html" rel="noreferrer">avoid memory leaks</a>.

blocks|key|1088320|text|戴夫，这是什么数据？如果它是属于整个应用程序的通用数据(例如:用户数据)，则扩展application类并将其存储在那里。如果数据与活动相关，则应该使用onSaveInstanceState和onRestoreInstanceState处理程序在屏幕旋转时持久化数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1088321|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Dave, what kind of data is it? If it's general data that pertains to the application as a whole (example: user data), then extend the Application class and store it there. If the data pertains to the Activity, you should use the onSaveInstanceState and onRestoreInstanceState handlers to persist the data on screen rotation.

blocks|key|873677|text|您可以创建application类并将所有数据保存在该类上，以便在应用程序中的任何位置使用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|873678|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You can create Application class and save your all data on that calss for use that anywhere in your application.

I'm working on a fairly complex Android application that requires a somewhat large amount of data about the application (I'd say a total of about 500KB -- is this large for a mobile device?). From what I can tell, any orientation change in the application (in the activity, to be more precise) causes a complete destruction and recreation of the activity. Based on my findings, the Application class does not have the same life-cycle (i.e. it is, for all intents and purposes, always instantiated). Does it make sense to store the state information inside of the application class and then reference it from the Activity, or is that generally not the "acceptable" method due to memory constraints on mobile devices? I really appreciate any advice on this topic. Thanks!

Using the Android Application class to persist data

Android

我正在开发一个相当复杂的Android应用程序，它需要相当多的关于应用程序的数据(我想总共大约500KB --对于移动设备来说是不是很大？)。据我所知，应用程序中的任何方向更改(更准确地说，在活动中)都会导致活动的完全破坏和重新创建。根据我的发现，Application类不具有相同的生命周期(即，无论出于何种目的，它都...

问使用Android Application类持久化数据
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