RecyclerView 不会填充

Question

调试后更新

事实证明，convertCursorToTransactionInfoList 和 transactionLoadComplete 从未真正运行过。我在它们上设置了断点，它们从未出现在调试器中。此外，adapterData: size = 0 会在运行调试器时显示。

我能够使用onCreateView 中TransactionInfo returnListValue = new TransactionInfo(); 下的代码正确填充回收站视图的一项

谁能提供一些关于为什么这不起作用的见解？我这样做的次数越来越多，我认为这与ArrayList<> 和List<> 的差异有关，因为ArrayList<> 用于TransactionsTab.java，而AdapterTransactions.java 使用List<> 或 TransactionInfo.java 在某些方面。我已经在下面发布了所有这些类。

SQLite 接口不是问题（我很确定），因为我在应用程序的其他地方使用它来使用SimpleCursorAdapter 填充Spinners。

TransactionsTab.java：

public class TransactionsTab extends Fragment
    implements TransactionLoad.LoadComplete {

RecyclerView transactionsRecycler;
AdapterTransactions adapter;
TransactionLoad load = null;
Cursor cursor;
ArrayList<TransactionInfo> adapterData = new ArrayList<>();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    load = new TransactionLoad(getActivity());
    load.execute();
}

@Override
public View onCreateView(LayoutInflater inflater,
                         @Nullable ViewGroup container,
                         @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.tab_transactions,container,false);
    transactionsRecycler = (RecyclerView) view.findViewById(R.id.transactionRecycler);
    adapter = new AdapterTransactions(getActivity(), adapterData);
    transactionsRecycler.setAdapter(adapter);
    transactionsRecycler.setLayoutManager(new LinearLayoutManager(getActivity()));

    TransactionInfo returnListValue = new TransactionInfo();
    returnListValue.itemName = "lunch";
    returnListValue.itemCat = "Food";
    returnListValue.itemCurrency = "KRW";
    returnListValue.itemPrice = "125";
    returnListValue.date = "2015/08/25; 17:25:32";
    adapterData.add(returnListValue);

    return view;
}

private void convertCursorToTransactionInfoList(Cursor cursor) {
    if (cursor != null) {
        while (cursor.moveToNext()) {
            TransactionInfo returnListValue = new TransactionInfo();
            returnListValue.itemName = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_NAME));
            returnListValue.itemCat = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CATEGORY));
            returnListValue.itemCurrency = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CURRENCY));
            returnListValue.itemPrice = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_PRICE));
            returnListValue.date = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_DATE));
            adapterData.add(returnListValue);
        }
    }
}

@Override
public void transactionLoadComplete(Cursor cursor) {
    convertCursorToTransactionInfoList(cursor);
    adapter.setData(adapterData);
    adapter.notifyDataSetChanged();
    adapter.transactionData.notifyAll();
}
}

AdapterTransactions.java：

public class AdapterTransactions extends RecyclerView.Adapter<AdapterTransactions.MyViewHolder> {

private LayoutInflater inflater;
List<TransactionInfo> transactionData = Collections.emptyList();

public void setData(List<TransactionInfo> newData) {
    transactionData = newData;
}

public AdapterTransactions(Context context, List<TransactionInfo> transactionData) {
    inflater = LayoutInflater.from(context);
    this.transactionData = transactionData;
}

@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = inflater.inflate(R.layout.transaction_row, parent, false);
    MyViewHolder holder = new MyViewHolder(view);
    return holder;
}

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    TransactionInfo current = transactionData.get(position);
    holder.itemName.setText(current.itemName);
    holder.itemCat.setText(current.itemCat);
    holder.itemPrice.setText(current.itemPrice);
    holder.itemDate.setText(current.date);
    holder.itemCurrency.setText(current.itemCurrency);
}

@Override
public int getItemCount() {
    return transactionData.size();
}

class MyViewHolder extends RecyclerView.ViewHolder {
    TextView itemName, itemCat, itemPrice, itemDate, itemCurrency;

    public MyViewHolder(View itemView) {
        super(itemView);
        itemName = (TextView) itemView.findViewById(R.id.itemName);
        itemCat = (TextView) itemView.findViewById(R.id.itemCat);
        itemPrice = (TextView) itemView.findViewById(R.id.itemPrice);
        itemDate = (TextView) itemView.findViewById(R.id.itemDate);
        itemCurrency = (TextView) itemView.findViewById(R.id.itemCurrency);
    }
}
}

TransactionInfo.java：

public class TransactionInfo {
public String itemName, itemPrice, itemCurrency, itemCat, date;
}

重新回答：

我已尝试对convertCursorToTransactionInfoList 进行以下方法更改：

private void convertCursorToTransactionInfoList(Cursor cursor) {
    if (cursor != null) {
        while (cursor.moveToNext()) {
            TransactionInfo returnListValue = new TransactionInfo();
            returnListValue.itemName = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_NAME));
            returnListValue.itemCat = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CATEGORY));
            returnListValue.itemCurrency = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CURRENCY));
            returnListValue.itemPrice = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_PRICE));
            returnListValue.date = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_DATE));
            adapterData.add(returnListValue);
        }
    }
}

和

private static void convertCursorToTransactionInfoList(Cursor cursor, ArrayList<TransactionInfo> adapterData) {
    if (cursor != null) {
        while (cursor.moveToNext()) {
            TransactionInfo returnListValue = new TransactionInfo();
            returnListValue.itemName = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_NAME));
            returnListValue.itemCat = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CATEGORY));
            returnListValue.itemCurrency = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CURRENCY));
            returnListValue.itemPrice = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_PRICE));
            returnListValue.date = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_DATE));
            adapterData.add(returnListValue);
        }
    }
}

像这样通知adatpers：

@Override
public void transactionLoadComplete(Cursor cursor) {
    convertCursorToTransactionInfoList(cursor, adapterData);
    adapter.setData(adapterData);
    adapter.notifyDataSetChanged();
    adapter.transactionData.notifyAll();
}

另外，请注意，我必须将 List<TransactionInfo> adapterData = new ArrayList<>(); 更改为 ArrayList<TransactionInfo> adapterData = new ArrayList<>();

我看的越多，我就越认为它与ArrayList<> 或List<> 问题有关。

结束编辑

Answer 1

问题在于从Cursor 中获取数据，特别是这里：

if (cursor.moveToFirst()) {
    for (int i = 10; i < cursor.getCount(); i++) {
        returnListValue.itemName = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_NAME));
        returnListValue.itemCat = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CATEGORY));
        returnListValue.itemCurrency = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CURRENCY));
        returnListValue.itemPrice = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_PRICE));
        returnListValue.date = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_DATE));
        returnList.add(returnListValue);
    }
}

上面的代码将光标移动到第一个位置（cursor.moveToFirst()），但之后Cursor 位置不会改变，因此您的循环执行cursor.getCount() 次，但它只对光标中的第一项进行操作.

相反，我会选择 while 循环而不是 for 循环，如下所示：

// move cursor on to next position if available
while(cursor.moveToNext()) { 
    // More data is available so add it to the list
    // process data as before
}

编辑 1

RE your comment - 这是我建议更改的内容。

代替：

adapterData = convertCursorToBudgetInfoList(cursor);

要么：

选项 1

convertCursorToBudgetInfoList 仍然是 static 方法，但现在在原始 adapterData 引用上运行。

convertCursorToBudgetInfoList(cursor, adapterData);

并将您的方法更改为：

private static void convertCursorToBudgetInfoList(Cursor cursor, ArrayList<TransactionInfo> adapterData) {

    if (cursor != null) {                         

        while (cursor.moveToNext()) { // note: no for loop ;-)
            TransactionInfo returnListValue = new TransactionInfo();
            returnListValue.itemName = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_NAME));
            returnListValue.itemCat = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CATEGORY));
            returnListValue.itemCurrency = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CURRENCY));
            returnListValue.itemPrice = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_PRICE));
            returnListValue.date = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_DATE));
            adapterData.add(returnListValue);
        }
    }
}

选项 2

将convertCursorToBudgetInfoList 设为成员方法而不是静态方法，并直接对您的adapterData 进行操作。

convertCursorToBudgetInfoList(cursor);

并将您的方法更改为：

private void convertCursorToBudgetInfoList(Cursor cursor) {

    if (cursor != null) {                         

        while (cursor.moveToNext()) { // note: no for loop ;-)
            TransactionInfo returnListValue = new TransactionInfo();
            returnListValue.itemName = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_NAME));
            returnListValue.itemCat = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CATEGORY));
            returnListValue.itemCurrency = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_CURRENCY));
            returnListValue.itemPrice = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_PRICE));
            returnListValue.date = cursor.getString(cursor.getColumnIndex(DatabaseHelper.TRANSACTION_DATE));
            adapterData.add(returnListValue); // member variable (same as this.adapterData)
        }
    }
}

当然，使用这些选项中的任何一个，请务必通知您的适配器。

我还要重申，您确实需要摆脱 for 循环 - 使用调试器逐步完成它，一切都会变得清晰。

Answer 2

尝试在convertCursorToBudgetInfoList 中更改此for 循环：

for (int i = 10; i < cursor.getCount(); i++) 

从0开始...如果少于 10 个结果将不会显示任何内容！

Answer 3

问题出在 TransactionsTab 上。在 transactionLoadComplete(Cursor cursor) 方法中，您更新了 Fragments List transactionData，但您从未将其传递给您的 RecyclerView Adapter。所以在你的适配器上调用 notify 没有任何作用，因为它的数据没有改变。

您的解决方案是在您的适配器中创建一个函数，例如：

public void setData(List<TransactionData> newData){
    transactionData = newData;
}

然后在transactionLoadComplete(Cursor cursor)中调用notifyDataSetChanged之前的新函数：

public void transactionLoadComplete(Cursor cursor) {
    adapterData = convertCursorToBudgetInfoList(cursor);
    adapter.setData(adapterData);
    adapter.notifyDataSetChanged();
    adapter.transactionData.notifyAll();
}