来自除main之外的其他布局的小部件上的空指针异常

I am trying to add various fragments to an Action bar Activity.

我正在尝试将各种片段添加到操作栏活动中。

Here is one of the fragments (nested inside the main activity):

这是一个片段(嵌套在主要活动中):

public static class ScheduleFragment extends Fragment {

    private static final String ARG_SECTION_NUMBER = "section_number";

    public static ScheduleFragment newInstance(int sectionNumber) {
        ScheduleFragment fragment = new ScheduleFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public ScheduleFragment(){
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View rootView = inflater.inflate(R.layout.schedule_layout, container, false);
        return rootView;
    }
}

And the respective xml:

和各自的xml:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text=""
        android:id="@+id/textView"/>
</RelativeLayout>

And when I call

当我打电话的时候

    titles.add((TextView) findViewById(R.id.textView));
    titles.get(0).setText(R.string.Departure_Location);

from within the MainActivity class, I get Null pointer exception, and I'm guessing that's because R.id.textView is defined in the "schedule_layout.xml" and not in the "main_activity.xml".

从MainActivity类中,我得到Null指针异常,我猜这是因为R.id.textView是在“schedule_layout.xml”中定义的,而不是在“main_activity.xml”中定义的。

Android studio checker finds the R.id.textView, even though I have no textView in the "main_activity.xml".

Android studio checker找到R.id.textView,即使我在“main_activity.xml”中没有textView。

So how exactly can I sort this out?

那么我怎么能解决这个问题呢?

1 个解决方案

#1

The answer to this is quite straightforward:

答案很简单:

Since I do

自从我这样做

View rootView = inflater.inflate(R.layout.schedule_layout, container, false);

I add the "schedule_layout" to the rootView, so basically, when I do

我将“schedule_layout”添加到rootView,基本上,当我这样做时

titles.add((TextView) findViewById(R.id.textView));

I tell the program to grab the textView from the main_activity layout, and since there is none, it returns null.

我告诉程序从main_activity布局中获取textView,因为没有,它返回null。

So I need to tell it to get it from schedule_layout, by:

所以我需要告诉它从schedule_layout获取它,通过:

titles.add((TextView) rootView.findViewById(R.id.textView));

#1