Question

我有一个Retrofit请求，该请求从我的API请求一个GroupAccount对象列表。该API会毫无问题地返回所有值，因此我尝试在活动中循环响应，这样可以完美地检索值，但是一旦调用

//groupAccounts is my list, declared and initialised globally, groupAccount is the object I create at the end of each iteration
groupAccounts.add(groupAccount);

它将所有groupAccount对象值设置为null。为什么会这样呢？

GroupAccount模型类中的构造函数：

public GroupAccount(long groupAccountId,
                  long adminId,
                  String accountName,
                  String accountDescription,
                  int numberOfMembers,
                  BigDecimal totalAmountPaid,
                  BigDecimal totalAmountOwed,
                  int testResourceId) {

}

具有onResponse和onFailure的请求方法：

public void getUserAssociatedAccounts(String userId){
Call<List<GroupAccount>> call = apiInterface.getUserAssociatedAccounts(userId);
call.enqueue(new Callback<List<GroupAccount>>() {
  @Override
  public void onResponse(Call<List<GroupAccount>> call, Response<List<GroupAccount>> response) {
    if(!response.isSuccessful()) {
      //Handle
    } else {
      if(response.body().size() > 0){
        for(int i=0; i<response.body().size(); i++) {

          //This is just for clarity
          long groupAccountId = response.body().get(i).getGroupAccountId();
          long adminId = response.body().get(i).getAdminId();
          String accountName = response.body().get(i).getAccountName();
          String accountDescription = response.body().get(i).getAccountDescription();
          int numberOfMembers = response.body().get(i).getNumberOfMembers();
          BigDecimal amountPaid = response.body().get(i).getTotalAmountPaid();
          BigDecimal amountOwed = response.body().get(i).getTotalAmountOwed();
          int testRes = R.drawable.human_photo;

          //Value setting works fine
          GroupAccount groupAccount = new GroupAccount(groupAccountId,
              adminId,
              accountName,
              accountDescription,
              numberOfMembers,
              amountPaid,
              amountOwed,
              testRes);

          //Values are now null here???
          groupAccounts.add(groupAccount);
        }
        setUpFAB();
        setUpNavDrawer();
        setUpAccountPreviewRecyclerView();
        emptyRVTextViewSetUp(checkIfListIsEmpty(groupAccounts));
      }
    }
  }

  @Override
  public void onFailure(Call<List<GroupAccount>> call, Throwable t) {

  }
});

}

在课程开始时，我的列表设置如下：

public class Home extends AppCompatActivity {

List<GroupAccount> groupAccounts = new ArrayList<>();
.
...rest of class
.
}

Answer 1

您尚未在构造函数中设置对象

您的代码：

public GroupAccount(long groupAccountId,
                  long adminId,
                  String accountName,
                  String accountDescription,
                  int numberOfMembers,
                  BigDecimal totalAmountPaid,
                  BigDecimal totalAmountOwed,
                  int testResourceId) {

}

正确的构造方法：

public GroupAccount(long groupAccountId,
                  long adminId,
                  String accountName,
                  String accountDescription,
                  int numberOfMembers,
                  BigDecimal totalAmountPaid,
                  BigDecimal totalAmountOwed,
                  int testResourceId) {

this.groupAccountId = groupAccountId;
this.adminId = adminId;
this.accountName = accountName;
this.accountDescription = accountDescription;
this.numberOfMembers = numberOfMembers;
this.totalAmountPaid = totalAmountPaid;
this.totalAmountOwed = totalAmountOwed;
this.testResourceId = testResourceId; 
}

来源：Java Contrsuctor

将对象添加到ArrayList会将对象值设置为null

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