java - ArrayAdapter 中的 createFromResources() 不能应用于微调器

Question

我在微调器上创建 ArrayAdapter 时遇到问题。我不知道如何向你们解释，但人们说一张图片能表达 1000 个单词。所以我提供了我的问题的图片。请帮助我，我真的不知道该怎么做。

这是我的类(class)

public class SettingFragment extends Fragment{

private View rootView;
Spinner spinner;
ArrayAdapter<CharSequence> adapter;

public SettingFragment(){
    //required empty public constructor
}

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

    spinner = (Spinner)rootView.findViewById(R.id.spinner);
    adapter = ArrayAdapter.createFromResource(this, R.array.select_font_size, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);

    return rootView;
}

这是我的 string.xml

<string-array name="select_font_size">
    <item>Small</item>
    <item>Default</item>
    <item>Large</item>
    <item>Larger</item>
</string-array>

这是我的xml代码

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">


<Spinner
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/spinner"
    android:layout_gravity="center_horizontal" />

Answer 1

我建议将适配器的创建移动到 onActivityCreated 回调中，当您确定通过调用 getActivity() 时您将获得一个非空实例 Activity 的:

public class SettingFragment extends Fragment{

private View rootView;
Spinner spinner;
ArrayAdapter<CharSequence> adapter;

public SettingFragment(){
    //required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    rootView = inflater.inflate(R.layout.fragment_setting, container, false);
    spinner = (Spinner)rootView.findViewById(R.id.spinner);

    return rootView;
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    adapter = ArrayAdapter.createFromResource(getActivity(), R.array.select_font_size, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spinner.setAdapter(adapter);
    }
}