Question

我使用此活动在表格布局中显示产品信息。当没有产品或没有产品信息时，当我开始此活动时，我得到一个空指针异常。我该如何处理？

 public void startSalesReportActivity() {

        Intent salesRepIntent = getMiAirlineActivity().getSalesReportActivityIntent();
        double netTotalValue = SalesUtil.calculateFlightTransactionTotal(purchaseDao, refundDao, getMiAirlineActivity());
        BigDecimal bigDecimal = new BigDecimal(netTotalValue);
        bigDecimal = bigDecimal.setScale(2, BigDecimal.ROUND_HALF_UP);
        salesRepIntent.putExtra(TOTAL_VALUE, String.valueOf(bigDecimal));
        startActivity(salesRepIntent);
    }

我在上述活动中调用此方法来计算我的产品信息。

 public static double calculateFlightTransactionTotal(PurchaseDao purchaseDao, PurchaseRefundDao purchaseRefundDao, AirlineActivity activity) {
        double purchaseAmount = calculateFlightLegPurchaseTransactions(purchaseDao, activity);
        double refundAmount = calculateFlightLegRefundTransactions(purchaseRefundDao, activity);
        double netAmount = purchaseAmount - refundAmount;
        return (netAmount > 0) ? netAmount : 0;
    }

导致NPE的行是双netTotalValue = ...

FATAL EXCEPTION: main
                                                             Process: com.miairline, PID: 8096
                                                             java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List com.miairline.model.PurchaseDao.getSuccessfulTransactions()' on a null object reference
                                                                 at com.miairline.utils.SalesUtil.calculateFlightLegPurchaseTransactions(SalesUtil.java:43)
                                                                 at com.miairline.utils.SalesUtil.calculateFlightTransactionTotal(SalesUtil.java:35)
                                                                 at com.miairline.settings.SettingsFragment.startSalesReportActivity(SettingsFragment.java:1134)
                                                                 at com.miairline.settings.SettingsFragment$22.onClick(SettingsFragment.java:1114)

Answer 1

将它放入if ... else语句中。例如，

if(value == null || value < 0)
{
      // Your code
}
else
{
}

或

if(!value==null)
{
      // Your code
}
else 
{
}

并且对于崩溃问题使用try..catch Block。

启动活动时出现空指针异常

1 个答案: