对于Activity来源$ C ​​$ C ，线3898（几乎底部）：

For the Activity source code, line 3898 (almost bottom):

/**
 * @hide
 */
public final boolean isResumed() {
    return mResumed;
}

这是什么 @hide 是什么意思？

我发现我的公共类ChildActivity延伸活动{...} 无法使用/看 Activity.isResumed（）。这正常吗？我怎样才能访问它？

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

请回答所有的三个问题。非常感谢！

Please answer all the three questions. Thanks a lot!

推荐答案

Android有两种类型的API无法通过SDK访问的。

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

第一个是位于包com.android.internal。第二个API类型是集合类和方法标有 @hide的javadoc属性。

The first one is located in package com.android.internal. The second API type is collection of classes and methods that are marked with @hide javadoc attribute.

隐藏的方法仍然可以通过Java反射来访问。该@hide属性的javadoc的只是其中的一部分（droiddoc也），所以@hide仅仅只是意味着该方法/类/场被排除在API文档。

The hidden methods can still be accessed via java reflection. The @hide attribute is just part of javadoc(droiddoc also), so the @hide just simply mean the method/class/field is excluded from the API docs.

例如，在ActivityManager.java的checkUidPermission方法是@hide。

For example, the checkUidPermission method in ActivityManager.java is @hide.

/** @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;
}

不过，我们可以通过反射调用它。

However, we can call it by reflection.

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});