java– 关于Android Firebase检索数据(没有setter 字段错误)

概述我只是想从我的firebase数据库中检索数据,但我不知道获取该数据的正确方法.这是我在androidstudio中的错误：W/ClassMapper:Nosetter/fieldforchapterTwofoundonclasscom.junburg.moon.rockbottom.model.ChapterW/ClassMapper:Nosetter/fieldforchatperOnefo

我只是想从我的firebase数据库中检索数据,但我不知道获取该数据的正确方法.这是我在android studio中的错误：

  W/ClassMapper: No setter/fIEld for chapterTwo found on class   com.junburg.moon.rockbottom.model.Chapter  W/ClassMapper: No setter/fIEld for chatperOne found on class   com.junburg.moon.rockbottom.model.Chapter  W/ClassMapper: No setter/fIEld for chapterTwo found on class   com.junburg.moon.rockbottom.model.Chapter  W/ClassMapper: No setter/fIEld for chapterOne found on class   com.junburg.moon.rockbottom.model.Chapter

这是我的数据类.这是Chapter.class模型.

public class Chapter {    private String chatername;    private String chaterExplain;    public Chapter() {    }    public Chapter(String chatername, String chaterExplain) {        this.chatername = chatername;        this.chaterExplain = chaterExplain;    }    public String getChatername() {        return chatername;    }    public voID setChatername(String chatername) {        this.chatername = chatername;    }    public String getChaterExplain() {        return chaterExplain;    }    public voID setChaterExplain(String chaterExplain) {        this.chaterExplain = chaterExplain;    }}

和Study.class模型

public class Subject {  private String subjectname;  private String subjectExplain;  private Chapter chapter;  public Subject() {  }  public Subject(String subjectname, String subjectExplain, Chapter    chapter) {    this.subjectname = subjectname;    this.subjectExplain = subjectExplain;    this.chapter = chapter;  }   public String getSubjectname() {      return subjectname;   }   public voID setSubjectname(String subjectname) {        this.subjectname = subjectname;   }   public String getSubjectExplain() {       return subjectExplain;   }    public voID setSubjectExplain(String subjectExplain) {       this.subjectExplain = subjectExplain;   }    public Chapter getChapter() {       return chapter;   }   public voID setChapter(Chapter chapter) {        this.chapter = chapter;   }}

这是我的addValueEventListener代码：

 private voID getStudyData() {      databaseReference.child("study")     .child("subject")     .addValueEventListener(new ValueEventListener() {      @OverrIDe      public voID onDataChange(DataSnapshot dataSnapshot) {        subjectList.clear();        for (DataSnapshot ds : dataSnapshot.getChildren()) {            Subject subject = ds.getValue(Subject.class);            subjectList.add(subject);            Log.d(TAG, "onDataChange: " +       subject.getChapter().getChatername()  +       subject.getChapter().getChaterExplain());        }        studyRecyclerAdapter.notifyDataSetChanged();    }    @OverrIDe    public voID onCancelled(DatabaseError databaseError) {    }});

最后,这是我在Firebase数据库中的JsON树.

我尝试了一些方法,但我无法解决这个错误.

代码执行不返回Chapter类数据.例如：

subject.getChapter().getChatername() subject.getChapter().getChaterExplain()

感谢您帮助我处理这个问题.谢谢你的关怀.

解决方法:

您的POJO类章节中有几个错误.首先,错误消息清楚地表明chapterOne和chapterTwo属性缺失.你需要在你的POJO中.

所以你的Chapter.java应该是这样的.

public class Chapter {    public ChapterOne chapterOne;    public ChapterTwo chapterTwo;}

ChapterOne和ChapterTwo类也需要定义.

public class ChapterOne extends ChapterDetails {}public class ChapterTwo extends ChapterDetails {}public class ChapterDetails {    public String chaptername;    public String chapterExplain;}

请注意,您已拼错了章节名称和章节pojo中的章节.当前变量名称是chatername和chaterExplain,这是错误的.请修复变量名称.

更新

But can i get data to change variable type in chapter data of subject
class? List.. Map.. or.. somethnig else like that. Not make new class
ChapterOne.. ChapterTwo..

使用您当前的实现,这是不可能的.但是,我建议您的firebase数据库实现稍作更改.让我们以章节点进行修改.

chapter    - chapterDetails        - chapterID : 1        - chaptername : Something one        - chapterExplain : Some explanation    - chapterDetails        - chapterID : 2        - chaptername : Something two        - chapterExplain : Some explanation

如果您像上面那样修改firebase数据库结构,那么您可能会遇到以下POJO类.

public class Chapter {    List<ChapterDetails> chapterDetails;}public class ChapterDetails {    public Long chapterID;    public String chaptername;    public String chapterExplain;}

I’m sorry I asked too much. But the same chapterDetail is not added to
the Firebases. I trIEd to add a chapterDetail with chapterID 1 and a
chapterDetail with chapterID 2, but it disappears or is replaced.

我刚刚展示了一个伪实现.对不起,如果更新的答案有误导性.但是,请使用以下内容在firebase数据库中设置数据.这样您就可以将数据作为firebase中的列表获取.

Firebase ref = new Firebase("<my-firebase-app>/chapter"):List<Chapter> chapterList = new ArrayList<Chapter>();// Now populate your chapterList with the chapters addItemsInYourChapterList();ref.setValue(chapterList); 

现在从firebase数据库中检索数据,如下所示.

ref.addValueEventListener(new ValueEventListener() {      @OverrIDe      public voID onDataChange(DataSnapshot snapshot) {          System.out.println("There are " + snapshot.getChildrenCount() + " chapters");          for (DataSnapshot chapterSnapshot: snapshot.getChildren()) {            Chapter chapter = chapterSnapshot.getValue(Chapter.class);            // Get your chapter details here.          }      }      @OverrIDe      public voID onCancelled(FirebaseError firebaseError) {          System.out.println("The read Failed: " + firebaseError.getMessage());      }  });

请注意,我只考虑章节点.根据需要修改代码.

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