如何檢索某些數據庫孩子和顯示的ListView

StudentInformation java類裏面。

public class StudentInformation { 

    String name; 
    String ID; 
    String studentID; 
    String email; 
    String phone_num; 

    public StudentInformation() { 

    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public String getID() { 
     return ID; 
    } 

    public void setID(String ID) { 
     this.ID = ID; 
    } 

    public String getStudentID() { 
     return studentID; 
    } 

    public void setStudentID(String studentID) { 
     this.studentID = studentID; 
    } 

    public String getEmail() { 
     return email; 
    } 

    public void setEmail(String email) { 
     this.email = email; 
    } 

    public String getPhone_num() { 
     return phone_num; 
    } 

    public void setPhone_num(String phone_num) { 
     this.phone_num = phone_num; 
    } 
}

我已經嘗試了很多方法，但仍的ListView沒有顯示和應用程序突然停止。

public class StudentInfoActivity extends AppCompatActivity { 

    //add Firebase Database stuff 
    private FirebaseDatabase mFirebaseDatabase; 
    private FirebaseAuth mAuth; 
    private FirebaseAuth.AuthStateListener mAuthListener; 
    private DatabaseReference myRef; 
    private String userID; 

    ListView mListView; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_student_info); 

     mListView = (ListView) findViewById(R.id.listview); 

     //declare the database reference object. This is what we use to access the database. 
     //NOTE: Unless you are signed in, this will not be useable. 
     mAuth = FirebaseAuth.getInstance(); 
     mFirebaseDatabase = FirebaseDatabase.getInstance(); 
     myRef = mFirebaseDatabase.getReference(); 
     FirebaseUser user = mAuth.getCurrentUser(); 
     userID = user.getUid(); 

     mAuthListener = new FirebaseAuth.AuthStateListener() { 
      @Override 
      public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) { 
       FirebaseUser user = firebaseAuth.getCurrentUser(); 
       if (user != null) { 
        // User is signed in 
        toastMessage("User Information"); 
       } else {} 
       // ... 
      } 
     }; //end authlistener 

     myRef.addValueEventListener(new ValueEventListener() { 
      @Override 
      public void onDataChange(DataSnapshot dataSnapshot) { 
       // This method is called once with the initial value and again 
       // whenever data at this location is updated. 
       showData(dataSnapshot); 
      } 

      @Override 
      public void onCancelled(DatabaseError databaseError) { 

      } 
     }); 
    } // end oncreate 

    private void showData(DataSnapshot dataSnapshot) { 
     for(DataSnapshot ds : dataSnapshot.getChildren()){ 
     StudentInformation sInfo = new StudentInformation(); 

      sInfo.setName(ds.child(userID).child("userInfo").getValue(StudentInformation.class).getName()); 
      sInfo.setID(ds.child(userID).child("userInfo").getValue(StudentInformation.class).getID()); 
      sInfo.setStudentID(ds.child(userID).child("userInfo").getValue(StudentInformation.class).getStudentID()); 
      sInfo.setEmail(ds.child(userID).child("userInfo").getValue(StudentInformation.class).getEmail()); 
      sInfo.setPhone_num(ds.child(userID).child("userInfo").getValue(StudentInformation.class).getPhone_num()); 

      ArrayList<String> array = new ArrayList<>(); 
      array.add(sInfo.getName()); 
      array.add(sInfo.getID()); 
      array.add(sInfo.getStudentID()); 
      array.add(sInfo.getEmail()); 
      array.add(sInfo.getPhone_num()); 
      ArrayAdapter adapter = new  ArrayAdapter(this,android.R.layout.simple_list_item_1,array); 
     mListView.setAdapter(adapter); 

     } 
    } //end showdata 

    @Override 
    public void onStart() { 
     super.onStart(); 
     mAuth.addAuthStateListener(mAuthListener); 
    } 

    @Override 
    public void onStop() { 
     super.onStop(); 
     if (mAuthListener != null) { 
      mAuth.removeAuthStateListener(mAuthListener); 
     } 
    } 

    private void toastMessage(String message){ 
     Toast.makeText(this,message,Toast.LENGTH_SHORT).show(); 
    } 
} // end class

這是我使用的代碼。我一直想知道getchildren方法，我在代碼中做了什麼錯誤？誰能幫我這個？

來源

2017-08-08 Didi Jaj

您可以FirebaseListAdapter。在這裏走，你不會有管理的任何更改或附加列表中的監聽器和一切被更新時，有服務器的任何變化

來源

2017-08-08 20:29:05

獲取數據，請使用如下代碼：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference(); 
DatabaseReference userInfoRef = rootRef.child("users").child(userID).child("userInfo"); 
ValueEventListener eventListener = new ValueEventListener() { 
    @Override 
    public void onDataChange(DataSnapshot dataSnapshot) { 
     String ID = ds.child("ID").getValue(String.class); 
     String email = ds.child("email").getValue(String.class); 
     String name = ds.child("name").getValue(String.class); 
     String phone_num = ds.child("phone_num").getValue(String.class); 
     String studentID = ds.child("studentID").getValue(String.class); 
     Log.d("TAG", ID + "/" + email + "/" + name + "/" + phone_num + "/" + studentID); 
    } 

    @Override 
    public void onCancelled(DatabaseError databaseError) {} 
}; 
userInfoRef.addListenerForSingleValueEvent(eventListener);

來源

2017-08-08 17:58:44

如何檢索某些數據庫孩子和顯示的ListView

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