Question

我在解析字符串到日期时遇到空指针异常。我使用simpledateformat进行解析。请参阅下面的代码并帮助我。

以下错误

日期dateFROM = formatter.parse（from2）;

代码 MainDatabaseHandler.java

`public List<String> getTimeSlotATT(String text2, String from2) {
        // TODO Auto-generated method stub
        List<String> list = new ArrayList<String>();
            SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");
            String selectQuery = "SELECT * FROM "+ TABLE_LABELS + " WHERE "+ KEY_NAME + " ='"+text2+"' AND "+FROM_DATE+"='"+from2+"'";
            String selectQuery1 = "SELECT * FROM "+ TABLE_LABELS + " WHERE "+ KEY_NAME + " ='"+text2+"'";
            SQLiteDatabase db = this.getReadableDatabase();  
            Cursor cursor = db.rawQuery(selectQuery, null);//selectQuery,selectedArguments  
            Cursor cursor1 = db.rawQuery(selectQuery1, null);
            // looping through all rows and adding to list  
            if (cursor.moveToFirst()) {  
                do {  

                    if(cursor.getString(6)==null){
                        list.add(null);
                    }
                    else if(cursor.getString(6)=="FULL DAY"){
                        list.add(cursor.getString(6));
                    }
                    else {
                        list.add(cursor.getString(6));
                    }

                } while (cursor.moveToNext());  
            }  

            if (cursor1.moveToFirst()) {  
                do {  
                        try {

                        Date dateFROM = formatter.parse(from2);
                        Date dateDB = formatter.parse(cursor1.getString(4));
                        Date dateDB1 = formatter.parse(cursor1.getString(5));


                        if(dateDB.after(dateFROM)){
                        }
                        else if(dateDB.before(dateFROM)){

                            if(dateDB1.equals(dateFROM)||dateDB1.after(dateFROM)){
                                list.add(cursor1.getString(6));
                            }
                            else if(dateDB1.before(dateFROM)){
                            }
                        }

                    } catch (ParseException e) {
                        e.printStackTrace();
                    }                   
                } while (cursor1.moveToNext());  
            } 
            // closing connection  
            cursor.close();  
            db.close();  

            // returning lables  
            return list; 
    }`

LogCat错误

`java.lang.NullPointerException
at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1009)
at java.text.DateFormat.parse(DateFormat.java:553)
at avi.MainDatabaseHandler.getIimeSlotAII(MainDatabase 45
Handler.java:580)
at avi.book_setup_usr.loadIimeSpinnerDataAII(book_setu 45
p_usr.java:460)
at avi.book_setup_usr.access$1(book_setup_usr.java:448 45
at avi.book_setup_usr$8.onClick(book_setup_usr.javaz77 45
7)
at com.android.internal.app.AlertControl1er$ButtonHand1er.handleMe 45
ssage(AlertController.java:166)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.ref1ect.Method.invokeNative(Native Method)
at java.lang.ref1ect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(Zygo 45
teInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)`

Answer 1

正如有人评论的那样，from2必须为null，或者它的格式可能与SimpleDateFormat对象中指定的格式不同。看看吧。

摘自SimpleDateFormat.parse(String text, ParsePosition pos)：

<强>返回：   从字符串解析的日期。如果出现错误，则返回null。

引发：NullPointerException - 如果text或pos为null。

Answer 2

首先确保from2不是null，而从db获取的数据不是null。

在添加成功和失败案例后，

String           from2            = "01-12-2015";
SimpleDateFormat simpleDateFromat = new SimpleDateFormat("dd-MM-yyyy");
Date dateFROM                     = simpleDateFromat.parse(from2);  
System.out.println("dateFROM : "+dateFROM);

在这里，您将获得正确的日期：Tue Dec 01 00:00:00 IST 2015

from2 = "2015-12-01";
dateFROM = simpleDateFromat.parse(from2);
System.out.println("dateFROM : "+dateFROM);

由于日期格式不正确，因此将其解析为：Tue Jun 07 00:00:00 IST 7

from2 = "";
dateFROM = simpleDateFromat.parse(from2);
System.out.println("dateFROM : "+dateFROM);

在这里，您将获得java.text.ParseException: Unparseable date: ""

from2 = null;
dateFROM = simpleDateFromat.parse(from2);
System.out.println("dateFROM : "+dateFROM);

在这里，您将获得java.lang.NullPointerException

解析字符串到目前为止的nullpointer异常

2 个答案: