关于空对象引用的（android.support.v4.widget.DrawerLayout $ DrawerListener）' [英] (android.support.v4.widget.DrawerLayout$DrawerListener)' on a null object reference
问题描述
你能帮我解决一下我的logcat上的这个错误吗？
http://pastebin.com/uSXruD54
Can you help me about this error on my logcat? http://pastebin.com/uSXruD54
其中：
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.setDrawerListener(android.support.v4.widget.DrawerLayout$DrawerListener)' on a null object reference
$ b我的Home课程第79行的$ b
是：
on my Home class at line 79 which is:
drawer.setDrawerListener(toggle);
http://pastebin.com/cixZ7d9d （MainActivity类，第48行）
http://pastebin.com/cixZ7d9d (MainActivity class, line 48)
我不知道setDrawerListener如何工作抱歉，我找到了stackoverflow上的同样问题：如何纠正v4.DrawerLayout中的NullPointerException？
I don't have any idea how setDrawerListener works sorry, I found the same problem here on stackoverflow: How to rectify NullPointerException in v4.DrawerLayout?
答案说它必须确保我在导航抽屉和布局文件中使用相同的ID，但我没有对其进行任何更改导航抽屉，因为它是我在Android Studio中选择的活动本身，我只是在其上实现了标签。
The answer says that it has to make sure that I'm using the same id for nav drawer and in layout file but I didn't made any changes on nav drawer because it's the activity itself that I chose in Android Studio, I just implemented tabs on it.
推荐答案
抽屉为空，大概是因为ID drawer_layout 的 DrawerLayout 不在 app_bar_home 布局。您应该只在 onCreate（）中调用 setContentView（）。第二个调用是使用 app_bar_home 布局完全替换 activity_home 布局。您的 DrawerLayout 不再在活动中，而 findViewById（）将返回null。
drawer is null, presumably because the DrawerLayout with ID drawer_layout is not in the app_bar_home layout. You should only be calling setContentView() once in onCreate(). The second call is completely replacing the activity_home layout with the app_bar_home layout. Your DrawerLayout is then no longer in the Activity, and the findViewById() will return null.
相反，< include> app_bar_home activity_home 中的布局，并删除第二个 setContentView（）调用。
Instead, <include> the app_bar_home layout in activity_home, and remove the second setContentView() call.
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