在firebase数据库中获取一个值并将其保存在一个变量中：android

问题描述：

我想为预订做一个应用程序。我需要在其他节点中查找一些数据，然后将其存储在一个变量中，并在其他节点处插入一个新的数据输入。这是我想要的数据结构：在firebase数据库中获取一个值并将其保存在一个变量中：android

{ 
"laundry_category" : { 
    "laundry_category1" : { 
     "name" : "clean laundry", 
     "description" : "xxxxxxx" 
    } 
}, 

"laundry" : { 
    "laundry_category1" : { 
     "laundry_id_1" : { 
     "name" : "ABC", 
     "colour" : "red", 
     "description" : "xxxxx" 
    } 
} 
}

例如，我想从衣物分类节点获取数据描述并将其插入到节点洗衣店。可能吗？我已经在我的代码中尝试过，但它不起作用。这是我的addLaundry.java代码：

addLaundry.java

DatabaseReference databaseLaundry; 
DatabaseReference databaseCategory; 

List<Laundry> laundryList; 

@Override 
protected void onStart() { 
    super.onStart(); 

    databaseLaundry.addValueEventListener(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot dataSnapshot) { 
      laundryList.clear(); 

      for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) { 
       Laundry laundry = postSnapshot.getValue(Laundry.class); 
       laundryList.add(laundry); 
      } 



      LaundryList adapter = new LaundryList(TambahLaundryActivity.this, laundryList); 
      listViewLaundry.setAdapter(adapter); 
     } 

     @Override 
     public void onCancelled(DatabaseError databaseError) { 

     } 
    }); 
} 

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


    btAddLaundry = (Button)findViewById(R.id.bn_add_laundry); 
    listViewLaundry = (ListView)findViewById(R.id.listViewLaundryLis); 

    laundryList = new ArrayList<>(); 


    Intent intentAddLaundry = getIntent(); 

    String id_category = intentAddLaundry.getStringExtra(MainActivity.category_id); 
    String description_category = intentTambahLaundry.getStringExtra(MainActivity.category_description); 

    databaseLaundry = FirebaseDatabase.getInstance().getReference("laundry").child(id_category); 

    databaseLaundry = FirebaseDatabase.getInstance().getReference("laundry").child(description_category); 

    btAddLaundry.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View view) { 
      addLaundry(); 
     } 
    }); 


} 

public void addLaundry() { 
    databaseLaundry.addValueEventListener(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot dataSnapshot) { 
      for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) { 
       category a = postSnapshot.getValue(category.class); 
       String var_category_description = ((Map)a).get("category_description").toString(); 

       String id = databaseLaundry.push().getKey(); 
       Laundry laundry = new Laundry(id, name_laundry, var_category_description); 
       databaseLaundry.child(id).setValue(laundry); 
      } 

     } 

     @Override 
     public void onCancelled(DatabaseError databaseError) { 

     } 
    }); 
    } 
}

Laundry.java

public class Laundry { 
    private String laundry_id; 
    private String laundry_nama; 
    private String laundry_alamat; 
    private String kategori_nama; 

public Laundry() { 

} 

public Laundry(String laundry_id, String laundry_name, String category_description { 
    this.laundry_id = laundry_id; 
    this.laundry_nama = laundry_nama; 
    this.category_description = category_description; 
} 

public String getLaundry_id() { 
    return laundry_id; 
} 

public String getLaundry_name() { 
    return laundry_name; 
} 

public String getLaundry_alamat() { 
    return laundry_alamat; 
} 

public String getCategory_description() { 
    return category_description; 
    } 
}

category.java

public class Category { 
private String category_id; 
private String category_name; 
private String category_description; 

public Category() { 

} 

public Category(String category_id, String category_name, category_description) { 
    this.category_id = category_id; 
    this.category_name = category_name; 
    this.category_description = category_description; 

} 

public String getcategory_id() { 
    return category_id; 
} 

public String getcategory_name() { 
    return category_name; 
} 

public String getcategory_description() { 
    return category_description; 
}

三江源这么多的帮助:)

您初始化'databaseLaundry'两次，这似乎是一个错误。但是请注意，Stack Overflow通常是调试器的糟糕替代品。如果您将问题分成单独的代码片段而无需外部依赖关系，那么最简单的方法是帮助解决问题，例如使用硬编码字符串代替从用户输入中读取的“description_category”。这种单独的片段被称为[MCVE]（http://*.com/help/mcve），是我们帮助您的最简单方式。 –

答

如果您希望将相同的数据保存在多个位置上，当您上传数据时，您需要在每个DatabaseReference对象上做相同的事情。因此，为了实现这一点，请使用此两个引用：

DatabaseReference idCateoryRef = FirebaseDatabase.getInstance().getReference("laundry").child(id_category);

和

DatabaseReference descriptionCategoryRef = FirebaseDatabase.getInstance().getReference("laundry").child(description_category);

在你的代码中的错误是，你初始化同DatabaseReference两次。如上所述，您需要针对每项操作有不同的DatabaseReference。

希望它有帮助。

在firebase数据库中获取一个值并将其保存在一个变量中：android

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