blocks|key|301242|text|Android有两种无法通过SDK访问的API。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|301243|第一个位于package+com.android.internal中。第二个API类型是用@hide+Javadoc+attribute标记的类和方法的集合。|offset|length|style|CODE|301244|从Android9(API28级)开始，谷歌引入了new+restrictions+on+the+use+of+non-SDK+interfaces，无论是直接、通过反射还是通过JNI。每当应用程序引用非SDK接口或尝试使用反射或JNI获取其句柄时，都会应用这些限制。|301245|但是在API级别28之前，隐藏的方法仍然可以通过Java反射来访问。@hide属性只是Javadoc+(也包括droiddoc)的一部分，所以@hide仅仅意味着方法/类/字段被排除在API文档之外。|301246|例如，ActivityManager.java中的checkUidPermission()方法使用@hide|301247|/**+@hide+*/
public+static+int+checkUidPermission(String+permission,+int+uid)+{
++++try+{
++++++++return+AppGlobals.getPackageManager()
++++++++++++++++.checkUidPermission(permission,+uid);
++++}+catch+(RemoteException+e)+{
++++++++//+Should+never+happen,+but+if+it+does...+deny!
++++++++Slog.e(TAG,+"PackageManager+is+dead?!?",+e);
++++}
++++return+PackageManager.PERMISSION_DENIED;
}|code-block|syntax|javascript|301248|但是，我们可以通过反射来调用它：|301249|Class+c;
c+=+Class.forName("android.app.ActivityManager");
Method+m+=+c.getMethod("checkUidPermission",+new+Class[]+{String.class,+int.class});
Object+o+=+m.invoke(null,+new+Object[]{"android.permission.READ_CONTACTS",+10010});|301250|entityMap|0|LINK|mutability|MUTABLE|url|https://code.google.com/p/doclava/wiki/JavadocTags#@hide|1|https://developer.android.com/about/versions/pie/restrictions-non-sdk-interfaces^0|0|D|K|19|N|0|0|P|1D|1|0|Y|5|1Z|5|0|3|K|P|K|1D|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@$D|1A|E|1B|1|1C]]|A|$]]|$1|H|3|I|5|6|7|1D|8|@]|9|@$D|1E|E|1F|1|1G]]|A|$]]|$1|J|3|K|5|6|7|1H|8|@$D|1I|E|1J|F|G]|$D|1K|E|1L|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1M|8|@$D|1N|E|1O|F|G]|$D|1P|E|1Q|F|G]|$D|1R|E|1S|F|G]]|9|@]|A|$]]|$1|N|3|O|5|P|7|1T|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|1U|8|@]|9|@]|A|$]]|$1|U|3|V|5|P|7|1V|8|@]|9|@]|A|$Q|R]]|$1|W|3|-4|5|6|7|1W|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]|14|$5|Z|10|11|A|$12|15]]]]

Android has two types of APIs that are not accessible via SDK.

The first one is located in package <code>com.android.internal</code>. The second API type is a collection of classes and methods that are marked with the <a href="https://code.google.com/p/doclava/wiki/JavadocTags#@hide" rel="noreferrer">@hide Javadoc attribute</a>. 

Starting from Android 9 (API level 28), Google introduces <a href="https://developer.android.com/about/versions/pie/restrictions-non-sdk-interfaces" rel="noreferrer">new restrictions on the use of non-SDK interfaces</a>, whether directly, via reflection, or via JNI. These restrictions are applied whenever an app references a non-SDK interface or attempts to obtain its handle using reflection or JNI. 

But before API level 28, the hidden methods could still be accessed via Java reflection. The <code>@hide</code> attribute is just part of Javadoc (droiddoc also), so the <code>@hide</code> just simply means the method/class/field is excluded from the API docs. 

For example, the <code>checkUidPermission()</code> method in <code>ActivityManager.java</code> uses <code>@hide</code>:

<pre><code>/** @hide */
public static int checkUidPermission(String permission, int uid) {
 try {
 return AppGlobals.getPackageManager()
 .checkUidPermission(permission, uid);
 } catch (RemoteException e) {
 // Should never happen, but if it does... deny!
 Slog.e(TAG, "PackageManager is dead?!?", e);
 }
 return PackageManager.PERMISSION_DENIED;
}
</code></pre>

However, we can call it by reflection: 

<pre><code>Class c;
c = Class.forName("android.app.ActivityManager");
Method m = c.getMethod("checkUidPermission", new Class[] {String.class, int.class});
Object o = m.invoke(null, new Object[]{"android.permission.READ_CONTACTS", 10010});
</code></pre>

For the <a href="https://android.googlesource.com/platform/frameworks/base/+/android-2.3.5_r1/core/java/android/app/Activity.java" rel="noreferrer"><code>Activity</code> source code</a>, line 3898 (close to the bottom):

<pre><code>/**
 * @hide
 */
public final boolean isResumed() {
 return mResumed;
}
</code></pre>

What does <code>@hide</code> mean?

I found my <code>public class ChildActivity extends Activity { ... }</code> cannot use/see <code>Activity.isResumed()</code>. Is this normal? How can I access it?

What does @hide mean in the Android source code?

Android

Java

对于，第398行(靠近底部)：/** * @hide */public final boolean isResumed() {    return mResumed;}@hide是什么意思？我发现我的public class ChildActivity extends Activity { ... }不能使用/查看Ac...

问在Android源代码中@hide是什么意思？
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问在Android源代码中@hide是什么意思？
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