那些仍然有问题的onAttach(活动活动)，它只是改变了上下文-

    @Override
public void onAttach(Context context) {
    super.onAttach(context);
    this.context = context;
}

在大多数情况下，保存上下文对您来说就足够了——例如，如果您想执行getResources()，您可以直接从上下文执行。如果你仍然需要将上下文放入你的活动中，那么就这样做吧

 @Override
public void onAttach(Context context) {
    super.onAttach(context);
    mActivity a; //Your activity class - will probably be a global var.
    if (context instanceof mActivity){
        a=(mActivity) context;
    }
}

由user1868713建议。

在commit()之后调用回调函数的顺序:

无论你在commit()之后手动调用什么方法 onAttach () onCreateView () onActivityCreated ()

我需要做一些涉及一些视图的工作，所以onAttach()不适合我;它坠毁。所以我移动了我的代码的一部分，设置一些参数在一个方法调用后立即提交()(1.)，然后在onCreateView()(3.)内处理视图的代码的另一部分。

Commit调度事务，也就是说，它不会立即发生，而是在下一次主线程准备就绪时在主线程上进行调度。

我建议加一个

onAttach(Activity activity)

方法，并在它上面放一个断点，看看它什么时候相对于你对asd()的调用被调用。您将看到它在您调用asd()退出的方法之后被调用。onAttach调用是片段附加到其活动的地方，从这一点上getActivity()将返回非空(注意还有一个onDetach()调用)。

The other answers that suggest keeping a reference to the activity in onAttach are just suggesting a bandaid to the real problem. When getActivity returns null it means that the Fragment is not attached to the Activity. Most commonly this happens when the Activity has gone away due to rotation or the Activity being finished but the Fragment still has some kind of callback listener registered preventing it from being garbage collected. When the listener gets called if you need to do something with the Activity but the Activity is gone there isn't much you can do. In your code you should just check getActivity() != null and if it's not there then don't do anything. If you keep a reference to the Activity that is gone you are preventing the Activity from being garbage collected. Any UI things you might try to do won't be seen by the user. I can imagine some situations where in the callback listener you want to have a Context for something non-UI related, in those cases it probably makes more sense to get the Application context. Note that the only reason that the onAttach trick isn't a big memory leak is because normally after the callback listener executes it won't be needed anymore and can be garbage collected along with the Fragment, all its View's and the Activity context. If you setRetainInstance(true) there is a bigger chance of a memory leak because the Activity field will also be retained but after rotation that could be the previous Activity not the current one.

在哪里调用这个函数?如果在Fragment的构造函数中调用它，它将返回null。

当onCreateView()方法被执行时，只需调用getActivity()。

自Android API级别23起，onAttach(Activity Activity)已弃用。你需要使用onAttach(Context Context)。http://developer.android.com/reference/android/app/Fragment.html onAttach (android.app.Activity)

Activity是一个上下文，所以如果你可以简单地检查上下文是否是一个Activity，并在必要时强制转换它。

@Override
public void onAttach(Context context) {
    super.onAttach(context);

    Activity a;

    if (context instanceof Activity){
        a=(Activity) context;
    }

}