JSON 解析后 Recyclerview 显示为空答案

【问题标题】：Recyclerview Shows Empty After JSON ParsingJSON 解析后 Recyclerview 显示为空
【发布时间】：2018-03-31 02:32:35
【问题描述】：

我必须从远程网络调用中显示 recyclerview 上的项目列表。我已经初始化了 recyclerview 并正确设置了它的布局管理器和适配器，但列表没有显示。

这是我的适配器类：

public class DashboardAdapter extends RecyclerView.Adapter<HomeDashboardHolder> {

private final Context context;
private List<HomeDashboard> itemsList;

public DashboardAdapter(Context context, List<HomeDashboard> itemsList) {
    this.context = context;
    this.itemsList = itemsList;
}

@Override
public HomeDashboardHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.home_dashboard_items_layout, parent, false);
    return new HomeDashboardHolder(view);
}

@Override
public void onBindViewHolder(HomeDashboardHolder viewholder, int position) {
    HomeDashboard dashboard = itemsList.get(position);
    viewholder.dashTitle.setText(dashboard.getDashTitle());
    Picasso.with(context)
            .load(dashboard.getDashIcon())
            .placeholder(R.drawable.noimage)
            .into(viewholder.dashIcon);
}

@Override
public int getItemCount() {
    if (itemsList == null) {
        return 0;
    }
    return itemsList.size();
 }
}

这是我目前的活动代码：

public class HomeActivity extends AppCompatActivity {

private static final String TAG = HomeActivity.class.getSimpleName();

private Toolbar toolbar;
private SwipeRefreshLayout swipeRefresh;
private RecyclerView dashboardRV, recyclerDrawer;
private DrawerLayout drawerLayout;

private List<DrawerItems> itemsList = new ArrayList<>();
private List<HomeDashboard> dashboardsList = new ArrayList<>();

private RecyclerView.LayoutManager layoutManager;
private RecyclerDrawerAdapter drawerAdapter;
private DashboardAdapter dashboardAdapter;
private String slug;
private int cartLength;

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

    init();
    setSupportActionBar(toolbar);

    initDrawer();

    setUpDashboard();

}

private void initDrawer() {
    recyclerDrawer.setHasFixedSize(true);
    recyclerDrawer.setLayoutManager(new LinearLayoutManager(this));

    DrawerItems drawerItems = new DrawerItems("Products", R.drawable.basket);
    itemsList.add(drawerItems);

    DrawerItems drawerItems1 = new DrawerItems("Cart", R.drawable.cart);
    itemsList.add(drawerItems1);

    DrawerItems drawerItems2 = new DrawerItems("Checkout", R.drawable.check_out);
    itemsList.add(drawerItems2);

    DrawerItems drawerItems3 = new DrawerItems("Profile", R.drawable.profile);
    itemsList.add(drawerItems3);

    DrawerItems drawerItems4 = new DrawerItems("Info", R.drawable.info);
    itemsList.add(drawerItems4);

    DrawerItems drawerItems5 = new DrawerItems("About", R.drawable.about);
    itemsList.add(drawerItems5);

    drawerAdapter = new RecyclerDrawerAdapter(this, itemsList);
    recyclerDrawer.setAdapter(drawerAdapter);

    toolbar.setNavigationIcon(R.drawable.burger_menu);
    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
                drawerLayout.closeDrawer(GravityCompat.START);
            } else {
                drawerLayout.openDrawer(GravityCompat.START);
            }
        }
    });

    setDrawerClickListener();

}

private void setDrawerClickListener() {
    recyclerDrawer.addOnItemTouchListener(new RecyclerItemTouchListener(this, recyclerDrawer, new RecyclerClickListener() {
        @Override
        public void onClick(View view, int position) {
            switch (position) {
                case 0:
                    startActivity(new Intent(HomeActivity.this, AllProductsActivity.class));
                    drawerLayout.closeDrawer(GravityCompat.START);
                    break;
                case 1:
                    startActivity(new Intent(HomeActivity.this, CartActivity.class));
                    drawerLayout.closeDrawer(GravityCompat.START);
                    break;
                case 2:
                    Intent intent = new Intent(HomeActivity.this, CheckOutActivity.class);
                    startActivity(intent);
                    drawerLayout.closeDrawer(GravityCompat.START);
                    break;
                case 3:
                    startActivity(new Intent(HomeActivity.this, ProfileActivity.class));
                    drawerLayout.closeDrawer(GravityCompat.START);
                    break;
                case 4:
                    Log.d(TAG, "Info Clicked");
                    break;
                case 5:
                    startActivity(new Intent(HomeActivity.this, AboutActivity.class));
                    drawerLayout.closeDrawer(GravityCompat.START);
                    break;
            }
        }

        @Override
        public void onLongClick(View view, int position) {

        }
    }));

}

private void init() {
    swipeRefresh = findViewById(R.id.swipeRefresh);
    toolbar = findViewById(R.id.toolbar);
    dashboardRV = findViewById(R.id.dashboardRV);
    recyclerDrawer = findViewById(R.id.recyclerDrawer);
    drawerLayout = findViewById(R.id.drawerLayout);
}

private void setUpDashboard() {

    dashboardRV.setHasFixedSize(true);
    layoutManager = new GridLayoutManager(HomeActivity.this, 2, GridLayoutManager.VERTICAL, false);
    dashboardRV.setLayoutManager(layoutManager);

    getHomeDash();

}

public void getHomeDash() {
    AndroidNetworking.get(Constants.CATEGORIES_ENDPOINT)
            .setTag("Get Categories Dashboard")
            .setPriority(Priority.HIGH)
            .build()
            .getAsJSONObject(new JSONObjectRequestListener() {
                @Override
                public void onResponse(JSONObject response) {
                    Log.d(TAG, "Categories Response:\t" + response.toString());

                    try {
                        JSONObject jsonObject = new JSONObject(response.toString());
                        final JSONArray categories = jsonObject.getJSONArray("categories");

                        for (int i = 0; i < categories.length(); i++) {
                            JSONObject object = categories.getJSONObject(i);

                            String id = object.getString("_id");
                            String title = object.getString("title");
                            String image = object.getString("image");
                            slug = object.getString("slug");

                            HomeDashboard dashboard = new HomeDashboard();
                            dashboard.setDashIcon(image);
                            dashboard.setDashTitle(title);
                            dashboard.setId(id);

                            dashboardsList.add(dashboard);

                        }
                        dashboardAdapter = new DashboardAdapter(getApplicationContext(), dashboardsList);
                        dashboardRV.setAdapter(dashboardAdapter);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                    dashboardAdapter.notifyDataSetChanged();

                }

                @Override
                public void onError(ANError anError) {
                    Log.d(TAG, "Request Failed:\t" + anError.getMessage());
                }
            });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.app_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.action_view_cart:
            startActivity(new Intent(HomeActivity.this, CartActivity.class));
    }
    return true;
}

@Override
protected void onResume() {
    super.onResume();

    if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
        drawerLayout.closeDrawer(GravityCompat.START);
    }

}

}

这是我对此活动的示例 json 响应：

D/HomeActivity: Categories Response:    {"success":true,"message":"All Categories","categories":[{"_id":"5aac46d8644ac63f14ffe89b","title":"Shrti","slug":"shrti","image":"http:\/\/res.cloudinary.com\/aapni-dukan\/image\/upload\/v1521239768\/categoryImages\/eBeSBYrG7MP7rW2Sa4qqQd06_lwakio.png"},{"_id":"5aac5b01d224ac3b801b9967","title":"Fruits","slug":"fruits","image":"http:\/\/res.cloudinary.com\/aapni-dukan\/image\/upload\/v1521244929\/categoryImages\/uWQT1XEplligclP4PrNC-Zyf_eamj8u.jpg"}]}

我正在 getHomeDash() 中初始化和设置适配器。我也打电话给notifyDataSetChanged()，但没有任何显示。

在日志中，为了检查列表是否为空，我将大小设为 2 但无法显示任何项目。我还尝试在调用getHomeDash() 之后将适配器设置为onCreate()，但屏幕上仍然没有显示任何内容。

Viewholder 类：

public class HomeDashboardHolder extends RecyclerView.ViewHolder {

public ImageView dashIcon;
public TextView dashTitle;

public HomeDashboardHolder(View itemView) {
    super(itemView);

    dashIcon = itemView.findViewById(R.id.dashIcon);
    dashTitle = itemView.findViewById(R.id.dashTitle);

}
}

有人可以帮我解决这个问题吗？谢谢

【问题讨论】：

你为什么在getHomeDash里面打电话dashboardAdapter.notifyDataSetChanged();评论notifyDataChanged然后试试
我已将其注释掉，但没有显示任何内容。有什么问题？
logcat 有什么错误吗？
未显示错误
发布你的适配器HomeDashboardHolderclass

标签： android android-recyclerview android-adapter jsonparser

【解决方案1】：

我认为您是在 getHomeDash() JSONObjectRequestListener 函数的工作线程中操作您的 UI ( notifyDataSetChanged() )。您应该在主线程中调用此函数，并检查 XML 中的 layout_height 和 layout_width。

【讨论】：

高度和宽度都可以。我已经注释掉了 notifyDataSetChanged 方法，但仍然没有显示

【解决方案2】：

对代码下方使用的回收器视图布局管理器集进行更改..

 dashboardRV.setLayoutManager(new GridLayoutManager(this, numberOfColumns,false));

【讨论】：

布局方向如何？

【解决方案3】：

您在创建DashboardAdapter 类的新对象后调用dashboardAdapter.notifyDataSetChanged();

notifyDataSetChanged(); 在您的列表适配器发生一些变化时使用

用户这个

layoutManager = new GridLayoutManager(HomeActivity.this,2);

不是这个

layoutManager = new GridLayoutManager(HomeActivity.this, 2, GridLayoutManager.VERTICAL, false);

【讨论】：