无法解析java.lang.NumberFormatException

Question

try{    
    if (flag_conv == false)
    {
      if ((Integer.parseInt(et1.getText().toString()))<=55)
      {
       final AlertDialog alertDialog = new AlertDialog.Builder(this).create();
       alertDialog.setTitle("Reset...");
       alertDialog.setMessage("WB should be grater than 55");

       alertDialog.setButton2("OK", new DialogInterface.OnClickListener() {
          public void onClick(DialogInterface dialog, int which) 
          {
                // here you can add functions
                dialog.dismiss();
          }});
       alertDialog.setIcon(R.drawable.icon);
       alertDialog.show();
       tv1.setText("WB");
       et1.setText("");
       wbflg = true;
       wbval = 0;
       return;          
     }
     else
     {                     
      wbval = Integer.parseInt(et1.getText().toString());
     }
   }
 catch(NumberFormatException nfe)
{System.out.println("Could not parse " + nfe);}

我得到了以下例外

07-31 14:48:45.409: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:50.569: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:54.599: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:54.829: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:54.958: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:55.108: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:55.259: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:48:55.409: DEBUG/dalvikvm(118): GREF has increased to 201
07-31 14:48:55.429: INFO/System.out(431): Could not parse java.lang.NumberFormatException: unable to parse '' as integer
07-31 14:52:43.798: DEBUG/SntpClient(58): request time failed: java.net.SocketException: Address family not supported by protocol

Answer 1

在Integer.parseInt

上

异常消息似乎如下：

07-31 14:48:45.409: INFO/System.out(431): Could not parse
   java.lang.NumberFormatException: unable to parse '' as integer

实际上，Integer.parseInt(String)无法解析空字符串。因此：

int num = Integer.parseInt("");
// throws java.lang.NumberFormatException: For input string: ""

如果您有isEmpty()或String s的任意null，那么您必须拥有特殊代码来处理它，因为Integer.parseInt(s)将始终抛出异常在那些情况下。

当Integer.parseInt(s)为s时，"xyz"当然可以抛出NumberFormatException。 try-catch，因此您可能希望将语句放在String s = ...; if (s == null || s.isEmpty()) { complaintAboutNotGettingAnything(); } else { try { int num = Integer.parseInt(s); doSomethingWith(num); catch (NumberFormatException e) { complaintAboutGettingSomethingYouDontWant(); } } 块中。

所以你可以这样写：

parseInt

---

编写易于调试的代码

在此特定代码段中，调用if ((Integer.parseInt(et1.getText().toString()))<=55) ... 似乎如下：

String et1text = et1.getText().toString();
// maybe check if it's empty/null if necessary
// maybe log/inspect what the value of et1text is for debugging

try {
   int et1val = Integer.parseInt(et1text);
   if (et1val <= THRESHOLD) {
      // ...
   }
} catch (NumberFormatException e) {
   moreComplaining();
}

在这一个表达中，很多事情都可能出错。我建议重构将这一点分解为逻辑可观察的步骤如下：

{{1}}

Answer 2

我不确定Java，但是如果你有可能不是有效的字符串的字符串 你可能有像C＃中的函数：

bool res = Int.TryParse(s,ref int);