Question

每当我切换布局时，片段都会从onCreateView中删除，这使我相信问题出在xml文件本身之内

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:orientation = "vertical"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="40dp"
        android:textColor="#FFFFFF"
        android:background="@color/lining"
        android:text="Añadir actividad"
        android:textStyle="bold"/>

    <view
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:layout_marginBottom="10dp"
        android:background="@color/lining" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="20dp"
            android:text="Nombre de actividad"
            android:textAlignment="center"/>

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="20dp"
            android:id="@+id/activity_name"/>
    </LinearLayout>

    <view
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:layout_marginBottom="10dp"
        android:layout_marginTop="10dp"
        android:background="@color/lining" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="20dp"
            android:text="Prioridad"
            android:textAlignment="center"/>

        <Spinner
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:textSize="20dp"
            android:id="@+id/priority"/>
    </LinearLayout>

    <view
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:layout_marginBottom="10dp"
        android:layout_marginTop="10dp"
        android:background="@color/lining" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <Button
            android:layout_marginTop="20dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Añadir fecha"
            android:id="@+id/date_select"/>

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/fecha"
            android:textSize="20dp"
            android:text="--/--/----"
            android:textAlignment="center"/>
    </LinearLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:src="@mipmap/ic_launcher" />

</LinearLayout>

AddFragment.java：

    public class AddFragment extends Fragment implements View.OnClickListener, DatePickerDialog.OnDateSetListener{

    EditText activityName;
    Spinner priority;
    Button dateSelected;
    TextView date;
    View v;
    Context context;
    CallBackToMain backToMain;
    Entrada modify;
    FloatingActionButton actionButton;
    String dateStrung = "";

    public static AddFragment newInstance(Entrada e) {
        Bundle args = new Bundle();
        args.putSerializable("entrada", e);

        AddFragment fragment = new AddFragment();
        fragment.setArguments(args);
        return fragment;
    }

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

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        this.context = context;
        backToMain = (CallBackToMain) context;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        instance();
        config();
        actions();
    }

    public void instance(){
        modify = (Entrada) getArguments().getSerializable("entrada");
        date = v.findViewById(R.id.fecha);
        dateSelected = v.findViewById(R.id.date_select);
        activityName = v.findViewById(R.id.activity_name);
        priority = v.findViewById(R.id.priority);
        actionButton = v.findViewById(R.id.save);
    }

    private void config(){
        if (modify != null){
            activityName.setText(modify.getNombreActividad());
            priority.setSelection(modify.getPrioridad());
            date.setText(modify.returnDateInFormat());
            String [] fullDateSplit = date.getText().toString().split("/");
            dateStrung = fullDateSplit[2] + fullDateSplit[1] + fullDateSplit[0];
        }
        String[] values =  {"Alta", "Media", "Baja"};
        priority.setAdapter(new ArrayAdapter(context, android.R.layout.simple_list_item_1, values));
    }

    private void actions(){
        actionButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.date_select){
            new DatePickerDialog(context, AddFragment.this,
                    Calendar.getInstance().get(Calendar.getInstance().YEAR),
                    Calendar.getInstance().get(Calendar.getInstance().MONTH),
                    Calendar.getInstance().get(Calendar.getInstance().DAY_OF_MONTH)).show();

        }

        else if (v.getId() == R.id.save){
            backToMain.backToMain(new Entrada(0, activityName.getText().toString(), (byte) priority.getSelectedItemPosition(), dateStrung));
        }
    }

    @Override
    public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
        //Si no, 0 es enero, 1 es febrero, etc.
        month++;
        //
        if(year < Calendar.YEAR || (year == Calendar.YEAR && month < Calendar.MONTH) || (year == Calendar.YEAR && month == Calendar.MONTH && dayOfMonth < Calendar.DAY_OF_MONTH)){
            new AlertDialog.Builder(context).setTitle("Fecha invalida").setMessage("Fecha anterior al día presente").show();
        }

        else{
            dateStrung = year + "" + month + "" + dayOfMonth;
            date.setText(dayOfMonth + "/" + month + "/" + year);
        }
    }

    public interface CallBackToMain{
        void backToMain(Entrada e);
    }
}

它只是停滞不前：

v = inflater.inflate(R.layout.addfragment, container, false);

错误java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference

我已经无数次地修改了Java和xml代码，但是我似乎找不到根本原因，而最重要的是它是一个字符串。等号似乎是最大的罪魁祸首，所以我根本不明白会发生什么...

有人可以帮我吗？我有点菜鸟，还不清楚呢^^;

Answer 1

这是一个简单的错字错误。因为您使用的是以下xml：

main()

这是错误的，因为它不是以大写开头。正确的一个：

 <view> .... </>

所以...。我试图替换SupportFragment，但是在onCreateView部分崩溃

1 个答案: