java - setOnClickListener(android.view.View$OnClickListener)' 在空对象引用上

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 4 年前。

我遇到了提交模式提交按钮的点击监听器问题。

这是错误。

FATAL EXCEPTION: main
              Process: com.kuryetaxi.omerkaptan.kuryetaxi, PID: 6564
              java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.button.MaterialButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

我对空指针异常是什么有一个合理的理解，并且我已经彻底搜索了与我类似的问题。我尝试以多种方式重新格式化点击监听器，确保我有正确的 View ID 等。

fragment 代码

View view;
private RecyclerView siparislerrecyclerview;
private SiparisAdapter siparisAdapter;
private List<SiparisModel> siparisList;
private ChangeFragments changeFragments;
private String siparis_id,kurye_id;
private GetSharedPreferences getSharedPreferences;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    view = inflater.inflate(R.layout.fragment_kurye_siparis, container, false);
    tanimla();
    gerek();
    getSip("0");

    return view;

}
public void tanimla()
{
    siparisList = new ArrayList<>();
    siparislerrecyclerview = view.findViewById(R.id.siparislerrecyclerview);
    RecyclerView.LayoutManager mng = new GridLayoutManager(getContext(),1);
    siparislerrecyclerview.setLayoutManager(mng);
    changeFragments = new ChangeFragments(getContext());
    getSharedPreferences = new GetSharedPreferences(getActivity());
    siparis_id=getSharedPreferences.getSession().getString("id",null);
}
public void getSip(String kur_durum)
{
    Call<List<SiparisModel>> req = getInstance().getSip(kur_durum);
    req.enqueue(new Callback<List<SiparisModel>>() {
        @Override
        public void onResponse(Call<List<SiparisModel>> call, Response<List<SiparisModel>> response) {
            Log.i("listem",response.body().toString());
            if (response.body().get(0).isTf())
            {
                siparisList = response.body();
                siparisAdapter = new SiparisAdapter(siparisList,getContext());
                siparislerrecyclerview.setAdapter(siparisAdapter);

            }
            else
            {
                Toast.makeText(getContext(),"FİRMA SİPARİSİ BULUNMAMAKTADIR",Toast.LENGTH_LONG).show();
                changeFragments.change(new HomeFragment());
            }
        }

        @Override
        public void onFailure(Call<List<SiparisModel>> call, Throwable t) {
            Toast.makeText(getContext(), Warnings.internetProblemText,Toast.LENGTH_LONG).show();

        }
    });
}

public void gerek()
{
    MaterialButton ekle = (MaterialButton)view.findViewById(R.id.ekleButton);
    ekle.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            siparisAl(siparis_id);

        }
    });
}

public void siparisAl(String siparis_id)
{

    Call<SiparisAlModel> req = ManagerAll.getInstance().siparisAl(siparis_id);
    req.enqueue(new Callback<SiparisAlModel>() {
        @Override
        public void onResponse(Call<SiparisAlModel> call, Response<SiparisAlModel> response) {
            Log.i("hatas",response.body().toString());
            Toast.makeText(getContext(),response.body().getText(),Toast.LENGTH_LONG).show();

        }

        @Override
        public void onFailure(Call<SiparisAlModel> call, Throwable t) {
            Toast.makeText(getContext(),Warnings.internetProblemText,Toast.LENGTH_LONG).show();

        }
    });
}

layout.xml代码

xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/siparisdetaylayout">

<android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    card_view:cardBackgroundColor="#f8b518"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    card_view:cardCornerRadius="10dp"
    card_view:cardElevation="1dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:clickable="true"
        android:id="@+id/siparisdetaylayout"
        android:layout_margin="6dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:layout_gravity="center"
        android:orientation="vertical">




        <de.hdodenhof.circleimageview.CircleImageView
            xmlns:app="http://schemas.android.com/apk/res-auto"
            android:layout_width="55dp"
            android:layout_height="55dp"
            android:layout_margin="15dp"
            android:id="@+id/logo"
            app:civ_border_width="2dp"
            app:civ_border_color="#FF000000"/>
        <TextView
            android:layout_gravity="left"
            android:layout_width="125dp"
            android:id="@+id/firmatext"

            android:textStyle="bold"
            android:textSize="17dp"
            android:gravity="left"
            android:textColor="#FF000000"
            android:layout_height="wrap_content" />



        <TextView
            android:layout_gravity="left"
            android:id="@+id/tarihtext"
            android:layout_width="125dp"

            android:textStyle="bold"
            android:textSize="17dp"
            android:gravity="left"
            android:textColor="#FF000000"
            android:layout_height="wrap_content" />
        <TextView
            android:layout_gravity="left"
            android:id="@+id/saattext"
            android:layout_width="125dp"

            android:textStyle="bold"
            android:textSize="17dp"
            android:gravity="left"
            android:textColor="#FF000000"
            android:layout_height="wrap_content" />

        <android.support.design.button.MaterialButton

            android:id="@+id/ekleButton"
            android:layout_width="wrap_content"
            android:layout_gravity="center"
            android:layout_marginTop="15dp"
            android:text="Ekle"
            style="@style/Widget.MaterialComponents.Button.UnelevatedButton"
            android:layout_height="wrap_content" />

    </LinearLayout>

</android.support.v7.widget.CardView>

Answer 1

重写类中的 onViewCreated() 方法，并将此方法 tanimla() gerek() getSip("0") 放入其中，并尝试在其中调用 getView()你的方法就像这样:

@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup  container, @Nullable Bundle savedInstanceState) {
    View view = LayoutInflater.from(getContext()).inflate(R.layout.fragment_kurye_siparis, container, false);
    return view;
}

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState){
    super.onViewCreated(view, savedInstanceState);
    //
    tanimla();
    gerek();
    getSip("0");
}

public void gerek()
{
    MaterialButton ekle = (MaterialButton)getView().findViewById(R.id.ekleButton);
    ...
}

阅读此内容doc !