android - 如何获取对象内矩阵的数据并在 RecyclerView 中可视化它们？
问题描述
我是 Android 问题的新手，并且出现了这个问题，因为我不知道如何获取对象内部排列的数据
这是我的网络服务的数据：
{"data":{"categories":[{"id":1,"name":"Whisky","photo":null,"photo_url":null,"created_at":"2018-07-06 17:28:15","updated_at":"2018-07-10 15:38:22"},{"id":2,"name":"Ron","photo":null,"photo_url":null,"created_at":"2018-07-10 15:37:56","updated_at":"2018-07-10 15:38:28"},{"id":3,"name":"Pisco","photo":null,"photo_url":null,"created_at":"2018-07-10 15:38:38","updated_at":"2018-07-10 15:38:38"},{"id":4,"name":"Vodka","photo":null,"photo_url":null,"created_at":"2018-07-10 15:38:44","updated_at":"2018-07-10 15:39:45"},{"id":5,"name":"Vino","photo":null,"photo_url":null,"created_at":"2018-07-10 15:39:56","updated_at":"2018-07-10 15:39:56"},{"id":6,"name":"Cerveza","photo":null,"photo_url":null,"created_at":"2018-07-10 15:40:02","updated_at":"2018-07-10 15:40:02"}]}}
我将 Json pojo 用于我的模型：
public class Category {
@SerializedName("data")
@Expose
private Data data;
public Data getData() {
return data;
}
public void setData(Data data) {
this.data = data;
}
@Override
public String toString() {
return "Category{" +
"data=" + data +
'}';
}
}
public class Category_ {
@SerializedName("id")
@Expose
private Integer id;
@SerializedName("name")
@Expose
private String name;
@SerializedName("photo")
@Expose
private Object photo;
@SerializedName("photo_url")
@Expose
private Object photoUrl;
@SerializedName("created_at")
@Expose
private String createdAt;
@SerializedName("updated_at")
@Expose
private String updatedAt;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Object getPhoto() {
return photo;
}
public void setPhoto(Object photo) {
this.photo = photo;
}
public Object getPhotoUrl() {
return photoUrl;
}
public void setPhotoUrl(Object photoUrl) {
this.photoUrl = photoUrl;
}
public String getCreatedAt() {
return createdAt;
}
public void setCreatedAt(String createdAt) {
this.createdAt = createdAt;
}
public String getUpdatedAt() {
return updatedAt;
}
public void setUpdatedAt(String updatedAt) {
this.updatedAt = updatedAt;
}
@Override
public String toString() {
return "Category_{" +
"id=" + id +
", name='" + name + '\'' +
", photo=" + photo +
", photoUrl=" + photoUrl +
", createdAt='" + createdAt + '\'' +
", updatedAt='" + updatedAt + '\'' +
'}';
}
}
public class Data {
@SerializedName("categories")
@Expose
private List<Category_> categories;
public List<Category_> getCategories() {
return categories;
}
public void setCategories(List<Category_> categories) {
this.categories = categories;
}
@Override
public String toString() {
return "Data{" +
"categories=" + categories +
'}';
}
}
然后我使用改造来获取数据，但我只是带来了对象，并且我只想使用该对象内部的数组来通过带有 AdapterView 的 RecyclerView 显示它
ApiService.java
@GET("/api/getCategories")
Call<Category> getCategories();
MainActivity.java
public class MainActivity extends AppCompatActivity{
private static final String TAG = MainActivity.class.getSimpleName();
private RecyclerView categoriesList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//HERE IS THE PROBLEM, I DONT KNOW HOW CREATE AN ADAPTER FOR CATEGORIES
categoriesList =(RecyclerView)findViewById(R.id.recyclerCategoryView);
categoriesList.setLayoutManager(new LinearLayoutManager(this));
//categoriesList.setAdapter(new CategoriesAdapter());
initialize();
}
private void initialize() {
ApiService service = ApiServiceGenerator.createService(ApiService.class);
Call<Category> call = service.getCategories();
call.enqueue(new Callback<Category>() {
@Override
public void onResponse(@NonNull Call<Category> call, @NonNull Response<Category> response) {
try {
int statusCode = response.code();
Log.d(TAG, "HTTP status code: " + statusCode);
if (response.isSuccessful()) {
Category categories = response.body();
Log.d(TAG, "Categorias: " + categories.getData().getCategories());
//THIS IS THE SAME PROBLEM
//CategoriesAdapter adapter = (CategoriesAdapter) categoriesList.getAdapter();
//adapter.setCategories(categories);
//adapter.notifyDataSetChanged();
} else {
Log.e(TAG, "onError: " + response.errorBody().string());
throw new Exception("Error en el servicio");
}
} catch (Throwable t) {
try {
Log.e(TAG, "onThrowable: " + t.toString(), t);
Toast.makeText(MainActivity.this, t.getMessage(), Toast.LENGTH_LONG).show();
}catch (Throwable x){}
}
}
@Override
public void onFailure(Call<Category> call, Throwable t) {
Log.e(TAG, "onFailure: " + t.toString());
Toast.makeText(MainActivity.this, t.getMessage(), Toast.LENGTH_LONG).show();
}
});
}
最后，我尝试做一个适配器，但是错了！！！
CategoriesAdapter.java
public class CategoriesAdapter extends RecyclerView.Adapter<CategoriesAdapter.ViewHolder> {
private Data listData;
public CategoriesAdapter(){
this.listData = new Data();
}
public void setCategories(Data listData){
this.listData = listData;
}
public class ViewHolder extends RecyclerView.ViewHolder{
public ImageView imagenCatView;
public TextView nombreCatText;
public ViewHolder(View itemView) {
super(itemView);
//imagenView = itemView.findViewById(R.id.picture_image);
nombreCatText = itemView.findViewById(R.id.name_cat_text);
}
}
@Override
public CategoriesAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_categories_products,
parent, false);
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(CategoriesAdapter.ViewHolder viewHolder, int position) {
Category_ category = this.listData.getCategories().get(position);
viewHolder.nombreCatText.setText(category.getName());
//viewHolder.precioText.setText("S/. " + product.getPrice());
//viewHolder.descripcionText.setText(product.getDescription());
//String url = ApiService.API_BASE_URL + "/images/" + product.getImage();
//Picasso.with(viewHolder.itemView.getContext()).load(url).into(viewHolder.imagenView);
}
@Override
public int getItemCount() {
return this.listData.getCategories().size();
}
}
错误：
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
at pe.bazan.jhosep.com.barapp.Adapters.CategoriesAdapter.getItemCount(CategoriesAdapter.java:66)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:3603)
at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:3103)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.widget.ScrollView.measureChildWithMargins(ScrollView.java:1286)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.widget.ScrollView.onMeasure(ScrollView.java:340)
at android.view.View.measure(View.java:18804)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
at android.view.View.measure(View.java:18804)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1060)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:400)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
at android.view.View.measure(View.java:18804)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
at android.view.View.measure(View.java:18804)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2112)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1228)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1464)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1119)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6060)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:606)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
at android.os.Handler.handleCallback(Handler.java:746)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(Zygot
解决方案
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