java - ArrayList IndexOfBound从firestore数据库获取数据时出现异常，为什么？

Question

我有一个 Recycler View，其中填充了 2 个数组列表，第一个是卡片 View 标题，第二个是其内容，问题发生在第二个数组列表中，例如，它从 firestore 接收数据。

下面是如何填充从本地云和字符串接收的数据数组列表的代码。

        valorCard.add(0, "R$: 16.402,98"); // must be added on first position

        DocumentReference dbRef = db.collection("Usuarios").document(firebaseAuth.getCurrentUser().getUid().toString());
        dbRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>(){
            @Override
            public void onSuccess(DocumentSnapshot documentSnapshot) {
                valorCard.add(1, documentSnapshot.get("quantBois").toString()); // must be added on second position
            }
        });
        valorCard.add(2,"25.000,00$"); // must be added on thrid position
        valorCard.add(3,"25/05/2020"); // must be added on fourth position

当代码运行时，返回:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.agrolucros2019, PID: 29318
    java.lang.IndexOutOfBoundsException: Index: 2, Size: 1
        at java.util.ArrayList.add(ArrayList.java:483)
        at com.example.agrolucros2019.fragmentos.home.HomeFragment.onCreateView(HomeFragment.java:65)
        at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2600)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:881)
        at androidx.fragment.app.FragmentManagerImpl.addAddedFragments(FragmentManagerImpl.java:2100)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1874)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1830)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
        at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2663)
        at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManagerImpl.java:2613)
        at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2624)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:904)
        at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
        at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2659)
        at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManagerImpl.java:2613)
        at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:246)
        at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:542)
        at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1395)
        at android.app.Activity.performStart(Activity.java:7361)
        at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3150)
        at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:180)
        at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:165)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:142)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:70)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1960)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7094)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)

我认为这是由于云中的数据请求需要一些时间来接收数据，并且由于我需要将数据准确地插入到第二个(1)位置，这会导致延迟，从而导致0 跳转到 2(因为 1 尚未填写)出错。

Answer 1

一个快速解决方法是在索引 2 和 3 中添加数据之前检查 ArrayList 的大小。如果尚未收到数据库中的数据，您可以:

1. 等待，当数据到达时，将其添加到索引 1，然后再添加 2 和 3

或者

将索引1设置为null，然后添加2和3并继续，当数据到达时它将替换null值

第二个选项的示例:

dbRef.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>(){
            @Override
            public void onSuccess(DocumentSnapshot documentSnapshot) {
                valorCard.add(1, documentSnapshot.get("quantBois").toString()); // must be added on second position
            }
        });
        if (valorCard.size() == 1){ // Check here
            valorCard.add(null);
        }
        valorCard.add(2,"25.000,00$"); // must be added on thrid position
        valorCard.add(3,"25/05/2020"); // must be added on fourth position