java - RecyclerView 不会填充

标签 java android sqlite android-recyclerview

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，但它们从未出现在调试器中。另外，adapterData: size = 0运行调试器时显示。

我能够使用onCreateView中的代码正确填充回收器 View 的一项。下TransactionInfo returnListValue = new TransactionInfo();

任何人都可以提供一些关于为什么这不起作用的见解吗？我这样做的次数越来越多，我认为这与ArrayList<>有关。和List<>差异是因为 ArrayList<>用于TransactionsTab.java而在 AdapterTransactions.java , List<>使用或 TransactionInfo.java在某些方面。我已在下面发布了所有这些类(class)。

SQLite 接口(interface)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填充 Spinners使用SimpleCursorAdapter 。

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);
        }
    }
}

像这样通知适配器:

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

另外，请注意我必须更改 List<TransactionInfo> adapterData = new ArrayList<>();至ArrayList<TransactionInfo> adapterData = new ArrayList<>();

我越看这个，我就越认为它与ArrayList<>有关。或List<>问题。

结束编辑

最佳答案

问题在于从 Cursor 中获取数据，特别是在这里:

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，因此您的循环被执行cursor.getCount() 次，但仅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

回复your comment - 这是我建议改变的。

而不是:

adapterData = convertCursorToBudgetInfoList(cursor);

或者:

选项 1

convertCursorToBudgetInfoList 仍然是静态 方法，但现在对原始 adapterData 引用进行操作。

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 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时，请确保通知您的适配器。

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

关于java - RecyclerView 不会填充，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34008455/

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