Android RecyclerView適配器未初始化

Question

起初為我的英語不好對不起。 我正在使用Android RecyclerView。 從我的Activity向服務器發送數據請求，並通過調用onCreate方法中的sendRequestForHistory（）方法從服務器獲取響應。 調用sendRequestForHistory（）之后，然后初始化我的數據適配器，但這里的ArrayList為空。 在sendRequestForHistory（）方法中，從服務器獲取數據並添加到ArrayList。 我的代碼是這樣的。

public class HistoryActivity extends AppCompatActivity {
private Toolbar toolbar;
private ProgressDialog PD;
private RecyclerView recyclerView;
private HistoryAdapter historyAdapter;
private Boolean isInternetPresent = false;
private ConnectionDetector cd;
private TextView tvEmptyView;
private ArrayList<ItemHistory> itemHistories;
protected Handler handler;
private LinearLayoutManager linearLayoutManager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_history);
    dbHelper= new DatabaseHelper(this);
    handler = new Handler();
    itemHistories = new ArrayList<ItemHistory>();

    toolbar = (Toolbar) findViewById(R.id.tool_bar);
    toolbar.setTitle(brandName);
    setSupportActionBar(toolbar);

    PD = new ProgressDialog(this);
    PD.setMessage("Loading.....");
    PD.setCancelable(false);
    recyclerView = (RecyclerView)findViewById(R.id.recycler_view_history);
    recyclerView.setHasFixedSize(true);
    linearLayoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(linearLayoutManager);

    sendRequestForHistory();

    // Here itemHistories is empty.
    historyAdapter = new HistoryAdapter(itemHistories, recyclerView);
    recyclerView.setAdapter(historyAdapter);
    historyAdapter.notifyDataSetChanged();
  } 

 private void sendRequestForHistory() {
 //send request to server and get response history data 
 // then history dada add to itemHistories ArrayList

 itemHistories.add(new ItemHistory(requestReceiver[i], requestAmount[i],requestCost[i]);

  }
}

Answer 1

希望對您有幫助，您正在撥打互聯網，這就是為什么當收到回復時您可以添加

private void sendRequestForHistory() {
    ApiClient.getArticles(page, category_name, type).enqueue(new Callback<List<Article>>() {
        @Override
        public void onResponse(Call<List<Article>> call, Response<List<Article>> response) {
            if(response.isSuccessfull()){
                for(Article article: response.body().getList()){
                    historyAdapter.addItem(article);
                }
            }else{
                Toast.makeText(getContext(),response.message(),Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onFailure(Call<List<Article>> call, final Throwable t) {
           Toast.makeText(getContext,t.getMessage(),Toast.LENGTH_LONG).show();
        }
    });
}

這是您的Adapter類，請在適配器的內部而不是外部添加“ Adding”功能，因為這會使您的代碼看起來更加糟糕和復雜。

public class HistoryAdapter{


private ArrayList<Article> articleList;

public HistoryAdapter(......){
   articleList = new ArrayList<>();
   .....
}

.....

.....


public void addItem(Article article){
    articleList.add(article);
    notifyDataSetChanged();
}
}