添加时，RecyclerView addInArray错误

6 回答

• 1

  使用

  adapter = new RecycleAdapter(listItems, CourierActivity.this);
  

  代替

  adapter = new RecycleAdapter(listItems, getApplicationContext());
  

  还要在 RecyclerView 中添加方向

  android:orientation="vertical"
  

  更新此：

  String rsp = new String(response.getBytes(), "UTF-8");
  

  回复于 2024-04-28T00:56:54+08:00
• 1

  试试这种方式

  CourierActivity.java

  public class CourierActivity extends AppCompatActivity {
      ...
     //Don't forget to intialize your List
      private List<OrderListItem> listItems = new ArrayList<OrderListItem>();
      ...
  
      private void loadOrdersData() {    
          RequestQueue queue = Volley.newRequestQueue(this);
          StringRequest sr = new StringRequest(Request.Method.GET, URL, new Response.Listener<String>() {
              @Override
              public void onResponse(String response) {
                  listItems = new ArrayList<>();
  
                  try {
                      String rsp = new String(response.getBytes("ISO-8859-1"), "UTF-8");
                      JSONArray orders = new JSONArray(rsp);
  
                      for (int i = 0; i < orders.length(); i++) {
                          OrderListItem listItem = new OrderListItem(
                                  // .. 
                          );
  
                          listItems.add(listItem);
                      }
                      //set list to adapter this way
                      adapter.setList(listItems);
                  } catch (JSONException | UnsupportedEncodingException e) {
                      e.printStackTrace();
                  }
              }
          }, new Response.ErrorListener() {
              @Override
              public void onErrorResponse(VolleyError error) {
                  Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_SHORT);
              }
          }) {
  
              @Override
              public Map<String, String> getHeaders() throws AuthFailureError {
                  Map<String, String> params = new HashMap<String, String>();
                  return params;
              }
          };
  
          queue.add(sr);
      }
      }
  

  RecycleAdapter.java

  public class RecycleAdapter extends RecyclerView.Adapter<RecycleAdapter.ViewHolder> {
  
      private List<OrderListItem> listItems;
      private Context context;
  
      public RecycleAdapter(List<OrderListItem> listItems, Context context) {
          this.listItems = listItems;
          this.context = context;
      }
  
      public setList(List<OrderListItem> listItems){
          //add list to parent list and notify your adapter
          this.listItems.addAll(listItems);
          notifyDataSetChanged();
      }
      ...
  }
  

  Edit 1 :

  main.xml

  <?xml version="1.0" encoding="utf-8"?>
  <LinearLayout  xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      tools:context="com.example.seether.myapplication.CourierActivity"
      android:background="#fff"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:id="@+id/drawerLayout">
  
      <android.support.v7.widget.RecyclerView
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:id="@+id/rv"/
  </LinearLayout>
  

  回复于 2024-04-28T00:56:54+08:00
• 1

  我做了几处修改并写了评论 . 试试看，

  public class CourierActivity extends AppCompatActivity {
      private TableLayout orderTable;
      private RecyclerView recyclerView;
      private RecycleAdapter adapter;
  
      //********* Initialize over here **********//
      private List<OrderListItem> listItems = new ArrayList<>();
      private Context mContext;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
          setContentView(R.layout.courier_main);
  
          //********** Initialize *******//
          mContext = CourierActivity.this;
  
          recyclerView = (RecyclerView) findViewById(R.id.rv);
          recyclerView.setHasFixedSize(true);
          recyclerView.setLayoutManager(new LinearLayoutManager(CourierActivity.this));
  
          //********* added class context *********//
          adapter = new RecycleAdapter(listItems, mContext);
          recyclerView.setAdapter(adapter);
          loadOrdersData();
      }
  
      private void loadOrdersData() {
          RequestQueue queue = Volley.newRequestQueue(this);
          StringRequest sr = new StringRequest(Request.Method.GET, URL, new Response.Listener<String>() {
              @Override
              public void onResponse(String response) {
                  //******** Remove this line *************//
                  listItems = new ArrayList<>();
  
                  //******** Add this line ************//
                  listItems.clear();
  
                  try {
                      String rsp = new String(response.getBytes("ISO-8859-1"), "UTF-8");
                      JSONArray orders = new JSONArray(rsp);
  
                      for (int i = 0; i < orders.length(); i++) {
                          OrderListItem listItem = new OrderListItem(
                                  // ..
                          );
  
                          listItems.add(listItem);
                      }
  
  
  
                      //*********Remove these both lines **********//
                      adapter = new RecycleAdapter(listItems, getApplicationContext());
                      recyclerView.setAdapter(adapter);
  
                      //************ Add this line **********//
                      adapter.notifyDataSetChanged();
  
                  } catch (JSONException | UnsupportedEncodingException e) {
                      e.printStackTrace();
                  }
              }
          }, new Response.ErrorListener() {
              @Override
              public void onErrorResponse(VolleyError error) {
                  Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_SHORT);
              }
          }) {
  
              @Override
              public Map<String, String> getHeaders() throws AuthFailureError {
                  Map<String, String> params = new HashMap<String, String>();
                  return params;
              }
          };
  
          queue.add(sr);
      }
  }
  

  回复于 2024-04-28T00:56:54+08:00
• 1

  Volley似乎是异步获取数据，因此管理 RecyclerView 的最合理方法是首先使用空（但不为空） List 和 Activity 上下文（例如 Mainactivity.this ）设置适配器 .

  当Volley终于得到了全部元素，你添加所有这些（而不是 for(int i = 0; i < orders.length(); i++) 你可以使用 for(OrderListItem listItem : orders); ），你可以调用 adapter.notifyDataSetChanged()

  回复于 2024-04-28T00:56:54+08:00
• 1

  而不是在 onResponse() 中创建新的 ArrayList 和 RecyclerAdapter 实例，我更喜欢，

  • 清除 listItems .

  • 将所有 OrderListItem 实例添加到 listItems .

  • adapter 的 notifyDataSetChanged() .

  例如：

  @Override
  public void onResponse(String response) {
       listItems.clear();
  
       try {
           //loop and add all items to listItems here
           adapter.notifyDataSetChanged();
       } catch (JSONException | UnsupportedEncodingException e) {
           e.printStackTrace();
       }
  }
  

  并确保正确初始化 RecyclerAdapter ，因为我没有在 CourierActivity 的 onCreate() 方法中看到任何创建 listItems 的代码 .

  listItems = new ArrayList<OrderListItem>();
   adapter = new RecycleAdapter(listItems, getApplicationContext());
  

  回复于 2024-04-28T00:56:54+08:00
• 1

  不要将 list 对象从活动传递给适配器 . 而是在适配器中有一个单独的数组列表 . 将适配器构造函数更改为：

  public RecycleAdapter(List<OrderListItem> listItems, Context context) {
           this.listItems = new ArrayList<>(listItems);
           this.context = context;
      }
  

  并且正如Maddy建议在适配器中使用setMethod传递listitem数组并向其添加所有项并调用notifyDataSetChanged .

  我想这应该解决你的问题，当你不在活动和适配器中使用相同的listitems对象 .

  回复于 2024-04-28T00:56:54+08:00