java - Android - 图像和文本无法加载(RecyclerView - CardView - API)

Question

我是 Android Studio 的初学者，这是我的第一个应用程序，问题:当我使用来自 Drawable 的图像和带有 RecyclerView 和 CardView 的本地文本启动应用程序时，效果很好但是当我使用 API JSON 时，应用程序可以正常工作而不显示任何内容这是我的代码

主要 Activity

public class MainActivity extends AppCompatActivity {

List<category> lstcategory;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    lstcategory = new ArrayList<>();
    AndroidNetworking.initialize(getApplicationContext());

           AndroidNetworking.get("https://api.myjson.com/bins/7r486")
            .setPriority(Priority.LOW)
            .build()
            .getAsJSONObject(new JSONObjectRequestListener() {
                @Override
                public void onResponse(JSONObject response) {
                    category cat = new category();
                    try{
                        JSONArray pj = response.getJSONArray("category");

                        for (int i=0;i< pj.length();i++)
                        {
                            JSONObject jb = pj.getJSONObject(i);
                            // cat.setImgURL(pj.getJSONObject(i).getString("imgUrl"));
                           // cat.setLibelle(pj.getJSONObject(i).getString("libelle"));
                            cat.setLibelle(jb.getString("libelle"));
                            cat.setImgURL(jb.getString("imgUrl"));

                        }

                    }
                    catch(JSONException e)
                    {
                        e.printStackTrace();
                    }
                    lstcategory.add(cat);// Add it to the end of the try section
                }

                @Override
                public void onError(ANError anError) {

                }
            });



    RecyclerView myrv = (RecyclerView) findViewById(R.id.recyclerview_id);
    RecyclerViewAdapter myAdapter = new RecyclerViewAdapter(this,lstcategory);
    myrv.setLayoutManager(new GridLayoutManager(this,3));
    myrv.setAdapter(myAdapter);

}

}

类别模态

public class category {

private String libelle;
private String imgURL;

public category() {
}

public String getLibelle() {
    return libelle;
}

public String getImgURL() {
    return imgURL;
}

public category(String libelle, String imgURL) {
    this.libelle = libelle;
    this.imgURL = imgURL;
}

public void setLibelle(String libelle) {
    this.libelle = libelle;
}

public void setImgURL(String imgURL) {
    this.imgURL = imgURL;
}

RecyclerViewAdapter

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> {

private Context mContext;
private List<category> mData;

public RecyclerViewAdapter(Context mContext, List<category> mData) {
    this.mContext = mContext;
    this.mData = mData;
}

@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
   View view;
    LayoutInflater mInflater = LayoutInflater.from(mContext);
    view = mInflater.inflate(R.layout.item_posts,parent,false);
    return new MyViewHolder(view);

}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
holder.tv_libelle.setText(mData.get(position).getLibelle());
holder.tv_imgURL.setText(mData.get(position).getImgURL());

}

@Override
public int getItemCount() {
    return mData.size();

}

public static class MyViewHolder extends RecyclerView.ViewHolder
{
    TextView tv_libelle;
    TextView tv_imgURL;

    public MyViewHolder(View itemView) {
        super(itemView);
        tv_libelle = (TextView) itemView.findViewById(R.id.libelle_layout);
        tv_imgURL = (TextView) itemView.findViewById(R.id.imgURL_layout);

    }
}

这是我的布局主要 Activity

    <?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerview_id"
        android:layout_width="match_parent"
        android:layout_height="match_parent">


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

</RelativeLayout>

CardView布局

 <?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="100dp"
    android:layout_height="120dp"
    android:layout_margin="5dp"
    card_view:cardCornerRadius="4dp"
    >


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

        <ImageView
            android:id="@+id/imgURL_layout"
            android:layout_width="100dp"
            android:layout_height="90dp"
            android:scaleType="centerCrop"
            android:background="#2d2d2d"

            />
        <TextView
            android:id="@+id/libelle_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="test"
            android:gravity="center"
            />

    </LinearLayout>


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

API JSON

[
{
    "id": 1,
    "libelle": "Développement pour l'entreprise",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/12/14599616875602_dev-entreprise.svg"
},
{
    "id": 2,
    "libelle": "Initiation numérique",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/13/14599617123358_initiation-numerique.svg"
},
{
    "id": 3,
    "libelle": "Marketing digital",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/14/14599617408214_marketing-digital.svg"
},
{
    "id": 4,
    "libelle": "Do it yourself",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/15/14599617668172_diy.svg"
},
{
    "id": 5,
    "libelle": "Gestion de projet",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/16/14599618101434_gestion-projet.svg"
},
{
    "id": 6,
    "libelle": "Entrepreneuriat",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/17/14599618766968_entreprise.svg"
},
{
    "id": 7,
    "libelle": "Développement web",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/18/14599618519803_developpement.svg"
},
{
    "id": 8,
    "libelle": "Développement mobile",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/19/14599619144036_dev-mobile.svg"
},
{
    "id": 9,
    "libelle": "Développement personnel",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/20/14599619404905_dev-perso.svg"
},
{
    "id": 10,
    "libelle": "Design",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/6/14599619912146_design.svg"
},
{
    "id": 11,
    "libelle": "Systèmes et réseaux",
    "description": "",
    "imgUrl": "https://s3-eu-west-1.amazonaws.com/course.oc-static.com/categories/21/14599619648729_systeme-reseau.svg"
},
{
    "id": 22,
    "libelle": "Autre",
    "description": "",
    "imgUrl": "http://static.oc-static.com/prod/images/categories/default_category_icon.svg"
}

]

我的目标是应用程序从 API 获取信息并显示它们!

Answer 1

这是因为您没有将类别对象添加到适配器中。在设置 cat 对象属性的 try-catch block 中，您需要将 cat 对象添加到 lstcategory 列表中。所以你基本上应该这样做:

lstcategory.add(cat);// Add it to the end of the try section

目前，您正在向 RecyclerView 传递一个空列表，这就是为什么它不显示任何项目，因为列表中没有元素。

除此之外，我建议您将类名称的第一个字母大写，因为这是标准约定，并且更易于阅读。