getActivity().findViewById(R.id.myId) 返回 Null

Question

因此，我尝试将自定义 XML 模板加载到 Fragment 中的 RelativeLayout，但 XML 视图返回 null。

我觉得我在这里缺少一个负责加载“description_fragment.xml”的类。如果这是真的，我应该从哪里开始？

这是我要加载布局的主要片段 （函数 loadDescription() 在这个 Fragment 创建之后被调用）：

public class ItemListFragment extends Fragment{

RelativeLayout relativeDescription;
item mItemDesc = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}



@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState){
    //The whole fragment
    RelativeLayout liste_item = (RelativeLayout)inflater.inflate(R.layout.fragment_liste_item,container,false);
    //The item description fragment
    relativeDescription = (RelativeLayout) inflater.inflate(R.layout.description_item,container, false);

    return liste_item;
}

public void loadDescription(int itemSelectonne) {
    //Http Request
    ItemClient client = ServiceGenerator.retrofit.create(ItemClient.class);
    Call<item> list = client.getDescriptionItem(Authentification.getXauth(), itemSelectonne);

    //Async Task
    list.enqueue(new Callback<item>() {
        @Override
        public void onResponse(Call<item> call, Response<item> response) {
            if(response.isSuccessful())
            {
                //Set response from request into (item) variable
                mItemDesc = response.body();
                //new var (data) used in case of Desync
                item data = mItemDesc;

                //Obtaining the RelativeView from the fragment_list_item.xml file
                relativeDescription = getActivity().findViewById(R.id.rl_Description);

                //Obtainaing all the Views inside description_item.xml
                TextView NomItem = getActivity().findViewById(R.id.tv_NomItem); //This returns null
                NomItem.setText(data.getNom());

                TextView DescriptionItem = getActivity().findViewById(R.id.tv_DescriptionItem);
                DescriptionItem.setText(data.getDescription());

                TextView PrixItem = getActivity().findViewById(R.id.tv_PrixItem);
                PrixItem.setText(data.getPrix());

                TextView TypeItem = getActivity().findViewById(R.id.tv_TypeItem);
                TypeItem.setText(data.getTypeItem());

                TextView NomMenu = getActivity().findViewById(R.id.tv_NomMenu);
                NomMenu.setText(data.getMenu().getNom());

                TextView TypeMenu = getActivity().findViewById(R.id.tv_TypeMenu);
                TypeMenu.setText(data.getMenu().getType());

            }
            else { /*HTTP Errors*/ }
            }
        }
        @Override
        public void onFailure(Call<item> call, Throwable t) { /*Message*/ }
    });
}
}

fragment_list_item.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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"
    tools:context=".UI.ItemListFragment">

<RelativeLayout
    android:id="@+id/rl_Description"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    />

description_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/rl_Description"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/border">


<TextView
    android:id="@+id/Label_Nom"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentStart="true"
    android:layout_alignParentTop="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    android:text="Nom de l'item:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/tv_NomItem"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/Label_Nom"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="5dp"
    tools:text="Burger" />

<TextView
    android:id="@+id/Label_Description"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_NomItem"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    android:text="Description de l'item:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/tv_DescriptionItem"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/Label_Description"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="5dp"
    tools:text="Allo le burger yer vrm bon: ceci est un exemple fyi" />

<TextView
    android:id="@+id/Label_Prix"
    android:layout_width="30dp"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_DescriptionItem"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    android:text="Prix:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/tv_PrixItem"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_DescriptionItem"
    android:layout_marginStart="5dp"
    android:layout_marginTop="12dp"
    android:layout_toEndOf="@+id/Label_Prix"
    tools:text="20$" />

<TextView
    android:id="@+id/Label_Type"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_DescriptionItem"
    android:layout_marginStart="24dp"
    android:layout_marginTop="12dp"
    android:layout_toEndOf="@+id/tv_PrixItem"
    android:text="Type d'item:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/tv_TypeItem"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_DescriptionItem"
    android:layout_marginStart="5dp"
    android:layout_marginTop="12dp"
    android:layout_toEndOf="@+id/Label_Type"
    tools:text="Le type de l'item ici" />

<TextView
    android:id="@+id/Label_Menu"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_TypeItem"
    android:layout_alignStart="@+id/Label_Nom"
    android:layout_marginTop="48dp"
    android:text="Menu que l'item fait partie:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/Label_MenuNom"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/Label_Menu"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    android:text="Nom du Menu:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/tv_NomMenu"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/Label_MenuNom"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="5dp"
    tools:text="Nom du menu ici" />

<TextView
    android:id="@+id/Label_TypeMenu"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tv_NomMenu"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    android:text="Type de menu:"
    android:textColor="@color/black" />

<TextView
    android:id="@+id/tv_TypeMenu"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/Label_TypeMenu"
    android:layout_alignParentStart="true"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    tools:text="Type du menu ici" />

Answer 1

您正在尝试通过活动查找视图，但您的活动不知道片段 xml 及其视图。

你应该做view.findViewById(id)，其中view是在onCreateView中创建的片段视图。

例如，您可以在 onCreateView 中定义所有视图并将其保存到变量中，然后您可以在 loadDescription 方法中对其进行交互。

public class ItemListFragment extends Fragment{

    RelativeLayout relativeDescription;
    TextView NomItem;
    TextView DescriptionItem;
    // and so on
    item mItemDesc = null;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        //The whole fragment
        View view = (RelativeLayout)inflater.inflate(R.layout.fragment_liste_item,container,false);
        //The item description fragment
        relativeDescription = (RelativeLayout) inflater.inflate(R.layout.description_item,container, false);

        NomItem = view.findViewById(R.id.tv_NomItem);
        DescriptionItem = view.findViewById(R.id.tv_DescriptionItem);
        // and so on

        return liste_item;
    }

    public void loadDescription(int itemSelectonne) {
        //Http Request
        ItemClient client = ServiceGenerator.retrofit.create(ItemClient.class);
        Call<item> list = client.getDescriptionItem(Authentification.getXauth(), itemSelectonne);

        //Async Task
        list.enqueue(new Callback<item>() {
            @Override
            public void onResponse(Call<item> call, Response<item> response) {
                if(response.isSuccessful())
                {
                    //Set response from request into (item) variable
                    mItemDesc = response.body();
                    //new var (data) used in case of Desync
                    item data = mItemDesc;

                    //This returns null
                    NomItem.setText(data.getNom());
                    DescriptionItem.setText(data.getDescription());
                    // and so on

                }
                else { /*HTTP Errors*/ }
            }
        }
        @Override
        public void onFailure(Call<item> call, Throwable t) { /*Message*/ }
    });
}