IllegalStateException: Fragment not attached to a context.

问题: java.lang.IllegalStateException: Fragment <...> not attached to a context.

根源: fragment 没有和 activity绑定, context为空.

参考: Fragment.java

@NonNull
public final Context requireContext() {
    Context context = getContext();
    if (context == null) {
        throw new IllegalStateException("Fragment " + this + " not attached to a context.");
    }
    return context;
}

解决办法: 可以在fragment内部，使用isAdded()来判断是否fragment和activity绑定。

if (fragmentA.isAdded()) {
    getText(R.string.myString);
}

注意：对于DialogFragment， DialogFragement.show()内部调用了FragmentTransaction.add()。所以在DialogFragement.show()之前，context是null

ref: 

https://blog.csdn.net/gengbaolong/article/details/103973804

https://blog.csdn.net/u012264122/article/details/50503886

https://www.jianshu.com/p/9e1dc12a1e65