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我有這個問題,我無法從我的firebase json獲取單個值,並檢查它是否爲null。Android Firebase獲得單個值作爲字符串
這裏是我的JSON文件:
{ "117500978158564407389":
{
"uid" : "117500978158564407389",
"cat_list" : {
"category_list" : [ {
"cat_name" : "Work"
}, {
"cat_name" : "Health"
}, {
"cat_name" : "Food"
}, {
"cat_name" : "Spare time"
}, {
"cat_name" : "Travel"
} ]
}
}
}
這是我在MVP的演示代碼,我嘗試在JSON讓我的「UID」值。但它始終顯示爲空。
@Override
public String getId(String id) {
reference = FirebaseDatabase.getInstance().getReferenceFromUrl("https://talisproject-89e62.firebaseio.com/userData/");
reference.child("117500978158564407389").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
CategoryList categoryList = dataSnapshot.getValue(CategoryList.class);
ID = categoryList.getUid();
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
return ID;
}
}
這裏是我的POJO類
public class CategoryList implements Serializable {
public List<Category> categoryList;
public List<Category> getCategoryList() {
return categoryList;
}
public void setCategoryList(List<Category> categoryList) {
this.categoryList = categoryList;
}
public CategoryList catList;
public String uid;
public String getUid() {
return uid;
}
public void setUid(String uid) {
this.uid = uid;
}
public CategoryList(CategoryList catList, String uid) {
this.catList = catList;
this.uid = uid;
}
}
,在這裏,我打電話給我演示功能,它總是顯示空。有誰知道,爲什麼它總是顯示一個null,我怎麼能得到這個值?
ID = interPresenter.getId(uid);
*有誰知道,爲什麼它總是顯示一個空* ...我知道...火力是異步http://ideone.com/PPHi95 ......顯然'返回ID;'出現在聽衆點擊'onDataChange'之前 – Selvin