我正在尝试设置适配器,但它给我的错误不是我在下面一行的onCreateView方法中的封闭类。
CustomAdapter adapter = new CustomAdapter(SecondYearFragment.this, sub);
这是我的Actvity.xml
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/content_main">
</FrameLayout>
<android.support.design.widget.BottomNavigationView
android:id="@+id/navigation"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginEnd="0dp"
android:layout_marginStart="0dp"
android:background="?android:attr/windowBackground"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:menu="@menu/navigation" />
这是fragment_third_year.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"
tools:context=".SecondYearFragment">
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/listviewthird"/></RelativeLayout>
这是sec_year_dept.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/image_below"
android:layout_width="match_parent"
android:layout_height="150dp"
android:src="@drawable/background_1" />
<TextView
android:id="@+id/dept_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:paddingBottom="@dimen/text_padding_top_bottom"
android:paddingLeft="@dimen/text_padding_left_right"
android:paddingRight="@dimen/text_padding_left_right"
android:paddingTop="@dimen/text_padding_top_bottom"
android:text="@string/app_name"
android:textSize="@dimen/text_size"
android:textStyle="bold" /></RelativeLayout>
这是ThirdYearFragment类
public class ThirdYearFragment extends Fragment {
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
ListView mListview;
String[] sub = {"random1", "random2", "random3", };
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public ThirdYearFragment() {
// Required empty public constructor
}
public static ThirdYearFragment newInstance(String param1, String param2) {
ThirdYearFragment fragment = new ThirdYearFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_third_year, container, true);
ListView listView = view.findViewById(R.id.listviewsecond);
CustomAdapter adapter = new CustomAdapter(SecondYearFragment.this, sub);
listView.setAdapter(adapter);
return view;
} }
这是我的自定义适配器
public class CustomAdapter extends ArrayAdapter<String> {
String[] subjects;
Context mContext;
public CustomAdapter(@NonNull Context context, String[] subjects) {
super(context, R.layout.sec_year_dept);
this.subjects = subjects;
this.mContext = context;
}
@Override
public int getCount() {
return subjects.length; //returns the size of the list
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
ViewHolder mViewHolder = new ViewHolder();
if(convertView == null) {
LayoutInflater mInflator = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = mInflator.inflate(R.layout.sec_year_dept, parent, false);
mViewHolder.mSubjects = (TextView) convertView.findViewById(R.id.dept_name);
mViewHolder.mSubjects.setText(subjects[position]);
convertView.setTag(mViewHolder);
}else {
mViewHolder = (ViewHolder) convertView.getTag();
}
return convertView;
}
static class ViewHolder {
TextView mSubjects;
}}
有人可以解释一下我发生了什么,我错过了什么?
答案 0 :(得分:1)
试试这个:
CustomAdapter adapter = new CustomAdapter(this.getContext(), sub);
您引用的是未在当前片段SecondYearFragment
中实例化的片段。所以它还没有上下文。
此外,片段不是上下文,因此即使它被实例化也不会起作用。
答案 1 :(得分:1)
使用CustomAdapter adapter = new CustomAdapter(getContext(), sub);
您使用的语法用于访问匿名类中的封闭类实例。 ThirdYearFragment不是SecondYearFragment的封闭类,这就是您收到此错误的原因。