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问RecylerView不会
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Stack Overflow用户

提问于 2015-11-30 21:36:04

回答 2查看 102关注 0票数 0

调试后更新

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

我能够正确地填充回收商视图中的一项内容，使用onCreateView中的TransactionInfo returnListValue = new TransactionInfo();代码。

有人能提供一些洞察为什么这将不起作用吗？我这么做的次数越多，我就认为这与ArrayList<>和List<>之间的关系有关，因为ArrayList<>在TransactionsTab.java中使用，而在AdapterTransactions.java中，List<>在某些方面被使用或TransactionInfo.java。我把这些课都贴在下面了。

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;
}

RE答案：

我尝试过对convertCursorToTransactionInfoList进行以下方法的修改

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);
        }
    }
}

通知这样的广告客户：

@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<>();改为ArrayList<TransactionInfo> adapterData = new ArrayList<>();

我越关注这个问题，我就越认为它与ArrayList<>或List<>问题有关。

端编辑

java

android

sqlite

android-recyclerview

回答 2

Stack Overflow用户

发布于 2015-12-01 03:26:35

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);
    }
}

上面的代码将游标移动到第一个位置(cursor.moveToFirst())，但在此之后，Cursor位置不会改变，因此循环被执行cursor.getCount()次，但它只对游标中的第一个项进行操作。

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 -以下是我建议的改变。

而不是：

adapterData = convertCursorToBudgetInfoList(cursor);

以下任一项：

备选案文1

convertCursorToBudgetInfoList仍然是一个static方法，但现在对原始adapterData引用进行操作。

convertCursorToBudgetInfoList(cursor, adapterData);

并将方法更改为：

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

使convertCursorToBudgetInfoList成为一个成员方法而不是静态方法，并直接对adapterData进行操作。

convertCursorToBudgetInfoList(cursor);

并将方法更改为：

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，使用这两个选项中的任何一个都要确保通知适配器。

我还要重申，您确实需要使用调试器来摆脱for循环步骤，一切都会变得清晰起来。

票数 2

Stack Overflow用户

发布于 2015-12-01 00:04:07

尝试在for中更改此convertCursorToBudgetInfoList循环

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

从0开始..。如果有不到10个结果，什么都不会出现！

票数 1

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/34008455

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