Question

我有两个具有相同类型的arraylist对象。想要通过进行必要的更改来将一个数据复制到另一个。但这会改变我的两个对象。以下是代码。

private ArrayList<Class_Summery_Enrollment> arrangeRecords(ArrayList<Class_Summery_Enrollment> source){
    ArrayList<Class_Summery_Enrollment> records = new ArrayList<Class_Summery_Enrollment>();
    ArrayList<Class_Meeting_Pattern_Enrollment> pattersList = new ArrayList<Class_Meeting_Pattern_Enrollment>();
    Class_Meeting_Pattern_Enrollment meetingPatternRec;
    Class_Summery_Enrollment rec = new Class_Summery_Enrollment();

    for(int i = 0 ;i<source.size();i++){
        if(source.get(i).getClass_MEETING_PATTERNS().size()>1){
            Log.v(Constants.TAG, "Total Patterns  = "+source.get(i).getClass_MEETING_PATTERNS().size());
            int size_ = source.get(i).getClass_MEETING_PATTERNS().size();
            for(int c = 0;c<size_;c++){
                rec = new Class_Summery_Enrollment();
                rec = source.get(i);
                if(c==0){
                    for (int k =0;k<source.get(i).getClass_MEETING_PATTERNS().size();k++){
                        pattersList.add(source.get(i).getClass_MEETING_PATTERNS().get(k));  
                    }
                }   
                rec.getClass_MEETING_PATTERNS().get(0).setSsr_INSTR_LONG(pattersList.get(c).getSsr_INSTR_LONG());
                rec.getClass_MEETING_PATTERNS().get(0).setSsr_MTG_LOC_LONG(pattersList.get(c).getSsr_MTG_LOC_LONG());
                rec.getClass_MEETING_PATTERNS().get(0).setSsr_MTG_DT_LONG(pattersList.get(c).getSsr_MTG_DT_LONG());
                rec.getClass_MEETING_PATTERNS().get(0).setSsr_MTG_SCHED_LONG(pattersList.get(c).getSsr_MTG_SCHED_LONG());
                records.add(rec);
            }
        }else{
            records.add(source.get(i));
        }
    }
    return records;

}

Answer 1

在Java中，当您说Object o1= o2;时，这意味着您正在尝试创建一个名为o1的新对象，其地址与o2相同。 SO ，您实际上只创建了一个对象，并在其上引用了两个对象。修改此对象将反映对象本身，并从任何对象地址访问它将产生相同的结果。

您需要使用Deep Copy的概念，手动复制真实值，而不是参考，Article来理解它

Answer 2

我通过在构造函数中传递自定义对象来解决它。在上面的代码中我分配了对其他对象的引用，因为它们都指向同一位置。以下代码将帮助您。

enter code here 
     private ArrayList<NormalizedClassRecords> reArrangeRecs( ArrayList<Class_Enrollment> source){      
     ArrayList<NormalizedClassRecords> records = new ArrayList<NormalizedClassRecords>();
     NormalizedClassRecords normalizedRec = new NormalizedClassRecords();
    for(int i=0;i<source.size();i++){
        NormalizedClassRecords rec = new NormalizedClassRecords(normalizedRec);
        rec.setCourseId(source.get(i).getCourseId());
        rec.setDescription(source.get(i).getDescription());
        for(int j=0;j<source.get(i).getAdviseclasses().size();j++){
            NormalizedClassRecords rec2 = new NormalizedClassRecords(rec);              
            rec2.setClassnbr(source.get(i).getAdviseclasses().get(j).getClassnbr());
            rec2.setRoomLocation(source.get(i).getAdviseclasses().get(j).getRoomLocation());
            rec2.setSubjectArea(source.get(i).getAdviseclasses().get(j).getSubjectArea());
            rec2.setSection(source.get(i).getAdviseclasses().get(j).getSection());
            rec2.setCatalogNbr(source.get(i).getAdviseclasses().get(j).getCatalogNbr());
            for(int k=0;k<source.get(i).getAdviseclasses().get(j).getMeetingPat().size();k++){
                NormalizedClassRecords rec3 = new NormalizedClassRecords(rec2);
                rec3.setInstructorName(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getInstructorName());
                rec3.setMeetingStartTime(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getMeetingStartTime());
                rec3.setMeetingEndTime(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getMeetingEndTime());
                rec3.setStartDate(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getStartDate());
                rec3.setEndDate(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getEndDate());
                rec3.setMonday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getMonday());
                rec3.setTuesday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getTuesday());
                rec3.setWednesday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getWednesday());
                rec3.setThursday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getThursday());
                rec3.setFriday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getFriday());
                rec3.setSaturday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getSaturday());
                rec3.setSunday(source.get(i).getAdviseclasses().get(j).getMeetingPat().get(k).getSunday());             
                records.add(rec3);
            }
        }
    }
    return records;
}

ArrayLists在Android中指向相同的对象或数据

2 个答案: