blocks|key|163574|text|instance永远不会初始化，因此它的默认值为null。这意味着instance.getContext()将抛出一个NullPointerException。要解决此问题，您需要初始化instance变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|163575|entityMap^0|0|8|O|4|X|L|1N|K|2L|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|G|$]]

<code>instance</code> is never initialized and so has a default value of <code>null</code>. This means that <code>instance.getContext()</code> will throw a <code>NullPointerException</code>. To fix this, you need to initialize the <code>instance</code> variable.

blocks|key|2966303|text|当前，您尚未初始化实例，默认情况下，它的值现在将设置为null。您需要为它赋值，然后才能使用它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2966304|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|$]]

Currently, you have not initialized instance and by default it's value would now be set to null. You need to assign it a value before you can use it.

blocks|key|163609|text|在OnCreate中创建Context的静态实例并保留它，直到您想要从getter方法getContext()获取它为止|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|163610|来自+Application+类的：|BOLD|163611|public+class+MyApp+extends+Application+{

private+static+Context+sContext;
@Override
public+void+onCreate()+{
++++sContext+=+getApplicationContext();
++++super.onCreate();
}

public+static+Context+getContext()+{
++++return+sContext;
}
}|code-block|syntax|javascript|163612|在您的+Manifest**:**中声明它|163613|<application+android:name="com.package.name.MyApp">|163614|entityMap^0|1|8|C|7|17|C|0|3|B|F|3|3|B|0|0|0|3|4|H|4|8|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@$9|11|A|12|B|H]|$9|13|A|14|B|H]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|I|3|J|5|K|7|17|8|@]|D|@]|E|$L|M]]|$1|N|3|O|5|6|7|18|8|@$9|19|A|1A|B|H]|$9|1B|A|1C|B|H]|$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|P|3|Q|5|K|7|1F|8|@]|D|@]|E|$L|M]]|$1|R|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]]|S|$]]

Create a static instance of the <code>Context</code> in your <code>OnCreate</code> and keep it till you want to get it from 
a getter method <code>getContext()</code>

From the <code>Application</code> class:

<pre><code>public class MyApp extends Application {

private static Context sContext;
@Override
public void onCreate() {
 sContext = getApplicationContext();
 super.onCreate();
}

public static Context getContext() {
 return sContext;
}
}
</code></pre>

Declare it in your <code>Manifest</code>:

<pre><code>&lt;application android:name="com.package.name.MyApp"&gt;
</code></pre>

blocks|key|163622|text|在onCreate()中创建一个getApplicationContext()+(mContext)的实例，然后在应用程序中的任何地方调用MyApp.getContext()，您将静态地获得应用程序上下文。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|163623|public+class+MyApp+extends+Application+{
+//private+static+MyApp+instance;
+private+static+Context+mContext;

++++public+static+MyApp+getInstance()+{
++++++++return+instance;
++++}

++++public+static+Context+getContext()+{
++++++//++return+instance.getApplicationContext();
++++++return+mContext;
++++}

++++@Override
++++public+void+onCreate()+{
++++++++super.onCreate();
++++//++instance+=+this;
+++++mContext+=+getApplicationContext();++++
++++}
}|code-block|syntax|javascript|163624|记得在你的AndroidManifest.xml中声明|163625|<application+android:name="com.mypackage.mypackage.MyApp">
...
...
...
</application>|163626|entityMap^0|1|A|G|N|15|8|1X|I|0|0|5|J|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|P|$]]

Create in <code>onCreate()</code> an instance of <code>getApplicationContext()</code> (<code>mContext</code>) then call <code>MyApp.getContext()</code> from everywhere in your app and you will get your application context statically.

<pre><code>public class MyApp extends Application {
 //private static MyApp instance;
 private static Context mContext;

 public static MyApp getInstance() {
 return instance;
 }

 public static Context getContext() {
 // return instance.getApplicationContext();
 return mContext;
 }

 @Override
 public void onCreate() {
 super.onCreate();
 // instance = this;
 mContext = getApplicationContext(); 
 }
}
</code></pre>

Remember to declare into your <code>AndroidManifest.xml</code>

<pre><code>&lt;application android:name="com.mypackage.mypackage.MyApp"&gt;
...
...
...
&lt;/application&gt;
</code></pre>

blocks|key|160959|text|使用以下方法获取应用程序上下文。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|160960|public+class+MyApp+extends+Application+{
++++private+static+MyApp+mAppInstance=null;
++++public+static+Context+appContext;
++++public+static+MyApp+getInstance()+{
++++++++return+mAppInstance;
++++}
++++public+static+MyApp+get()+{
++++++++return+get(appContext);
++++}
++++public+static+MyApp+get(Context+context)+{
++++++++return+(MyApp)+context.getApplicationContext();
++++}
++++@Override
++++public+void+onCreate()+{
++++++++super.onCreate();
++++++++mAppInstance=this;
++++++++appContext=getApplicationContext();

++++}
}|code-block|syntax|javascript|160961|在清单文件中添加应用程序名称|offset|length|style|BOLD|160962|<application+android:name="packagename.MyApp"/>|160963|要获取上下文，请使用MyApp.getInstance().getApplicationContext()|CODE|160964|entityMap^0|0|0|1|2|0|0|A|17|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|V|8|@$I|W|J|X|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Z|8|@$I|10|J|11|K|Q]]|9|@]|A|$]]|$1|R|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|S|$]]

Use the following way to get the Application context.

<pre><code>public class MyApp extends Application {
 private static MyApp mAppInstance=null;
 public static Context appContext;
 public static MyApp getInstance() {
 return mAppInstance;
 }
 public static MyApp get() {
 return get(appContext);
 }
 public static MyApp get(Context context) {
 return (MyApp) context.getApplicationContext();
 }
 @Override
 public void onCreate() {
 super.onCreate();
 mAppInstance=this;
 appContext=getApplicationContext();

 }
}
</code></pre>

add the the application name inside the Manifest file

<pre><code>&lt;application android:name="packagename.MyApp"/&gt;
</code></pre>

to get the context use 
<code>MyApp.getInstance().getApplicationContext()</code>

blocks|key|162283|text|另一个根本原因是备份过程中的错误。请参阅|type|unstyled|depth|inlineStyleRanges|entityRanges|data|162284|Why+backup+related+process+might+cause+Application's+onCreate+is+not+executed?|offset|length|162285|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/57211036/why-backup-related-process-might-cause-applications-oncreate-is-not-executed/57246212^0|0|0|26|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Another root cause, is due to the buggy backup process. Please refer to 

<a href="https://stackoverflow.com/questions/57211036/why-backup-related-process-might-cause-applications-oncreate-is-not-executed/57246212">Why backup related process might cause Application&#39;s onCreate is not executed?</a>

The following schema has been touted as the way to get application context from anywhere within my android app. But sometimes doing <code>MyApp.getContext()</code> returns null. I tried changing the schema by removing <code>static</code> from <code>getContext()</code> so that I would do <code>MyApp.getInstance().getContext()</code>. It still returns null. How do I fix this? How do I get my application's context from anywhere within my app?

<pre><code>public class MyApp extends Application {
 private static MyApp instance;

 public static MyApp getInstance() {
 return instance;
 }

 public static Context getContext() {
 return instance.getApplicationContext();
 }

 @Override
 public void onCreate() {
 super.onCreate();
 instance = this;
 }
}
</code></pre>

Get application context returns null

下面的模式被吹捧为从我的android应用程序中的任何地方获取应用程序上下文的方法。但有时执行MyApp.getContext()会返回null。我尝试通过从getContext()中删除static来更改模式，以便执行MyApp.getInstance().getContext()。它仍然返回null。如何修复此问题...

问获取应用程序上下文返回null
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