EditText 不会向 Spinner 添加数据

Question

我有一个片段要求用户输入主题，然后将其保存到 Spinner 中。问题是当我按下添加时，没有任何反应。我有一条 toast 消息来检查它是否已添加，但均未显示。我相信我做错了什么，因为我有一个片段，代码可能与我习惯的不同。我的 MainActivity class 中没有与此相关的内容。我是初学者，所以我不太了解，任何帮助将不胜感激，谢谢。

我的片段代码：


public class SubjectFragment extends Fragment {

    Spinner sp;
    RecyclerView recyclerView;
    FloatingActionButton newTaskBtn;
    EditText addSubjectEntry;
    Button addSubBtn, deleteBtn;
    myDatabase myDB;
    ArrayList<String> subjects = new ArrayList<String>();
    ArrayAdapter<String> adapter;


    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_message, container, false);
        sp = view.findViewById(R.id.addSubjectSpinner);
        addSubBtn = view.findViewById(R.id.addSubBtn);
        addSubjectEntry = view.findViewById(R.id.addSubjectEntry);
        deleteBtn = view.findViewById(R.id.deleteBtn);

        adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_dropdown_item_1line, subjects);
        sp.setAdapter(adapter);
        sp.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int pos, long id) {
                addSubjectEntry.setText(subjects.get(pos));
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });
        addSubBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                add();
            }
        });
        deleteBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                delete();
            }
        });

        return inflater.inflate(R.layout.fragment_message, container, false);

    }

    private void add() {
        String subject = addSubjectEntry.getText().toString();
        if (!subject.isEmpty() && subject.length() < 0) {
            adapter.add(subject);
            adapter.notifyDataSetChanged();
            addSubjectEntry.setText("");
            Toast.makeText(getActivity(), "Added", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(getActivity(), "Nothing to add!", Toast.LENGTH_SHORT).show();
        }
    }

    private void delete() {
        int pos = sp.getSelectedItemPosition();
        if (pos > -1) {
            adapter.remove(subjects.get(pos));
            adapter.notifyDataSetChanged();
            Toast.makeText(getActivity(), "Deleted", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(getActivity(), "Nothing to delete!", Toast.LENGTH_SHORT).show();
        }
    }
}

XML 文件:

<androidx.constraintlayout.widget.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:layout_width="match_parent"
    android:layout_height="match_parent">


    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="80dp"
        android:text="Add/Delete Subjects"
        android:textSize="20dp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Spinner
        android:id="@+id/addSubjectSpinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="60dp"
        android:layout_marginEnd="100dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <EditText
        android:id="@+id/addSubjectEntry"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="60dp"
        android:layout_marginEnd="100dp"
        android:hint="Subject Name"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/deleteBtn" />

<!--    <view-->
<!--        android:id="@+id/view"-->
<!--        android:layout_width="match_parent"-->
<!--        android:layout_height="1dp"-->
<!--        android:layout_marginTop="60dp"-->
<!--        app:layout_constraintTop_toBottomOf="@+id/deleteBtn"-->
<!--        tools:layout_editor_absoluteX="0dp" />-->

    <Button
        android:id="@+id/addSubBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:text="@string/add"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/addSubjectEntry"
        android:textAllCaps="false"/>

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/Subject"
        app:layout_constraintBottom_toTopOf="@+id/addSubjectSpinner"
        app:layout_constraintStart_toStartOf="@+id/addSubjectSpinner" />

    <Button
        android:id="@+id/deleteBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="60dp"
        android:text="Delete"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/addSubjectSpinner"
        android:textAllCaps="false"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

您已经创建了两次布局。你膨胀你的第一个布局，设置点击监听器到布局的视图，然后创建另一个布局，这就是什么都没有发生的原因。只需替换 onCreateView 方法中的最后一行：

    return inflater.inflate(R.layout.fragment_message, container, false);

和

return view;

EditText 不会向 Spinner 添加数据

EditText wont add data to Spinner

android

android-spinner