我正在使用以下 Firebase 数据库表开发 Android 应用程序:
"posts": {
"id_1": {
"author": "google:111527135678918251124",
"color": -2960686,
"creationTime": 1427104145195,
"text": "my text",
"title": "my Title",
"type": 0,
"visible": true
},
"id_2": {
"author": "google:111527135678918251524",
"color": -2960686,
"creationTime": 1427104145195,
"text": "my text",
"title": "my Title",
"type": 2,
"visible": true
},
"id_3": {
"author": "google:111527135678918251124",
"color": -2960686,
"creationTime": 1427104145195,
"text": "my text",
"title": "my Title",
"type": 1,
"visible": true
}
}
我希望能够检索按子项排序的帖子(例如按类型排序),并能够检索具有特定子值(类型= 1)的所有帖子。
阅读 Firebase 文档,我似乎必须编写以下代码,但没有得到想要的结果。
按类型排序
rootRef.child("posts").orderByChild("type")
.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
result = (HashMap<String, Post>) dataSnapshot.getValue();
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
我得到:无序的帖子地图
类型=值
rootRef.child("posts").orderByChild("type").equalTo(1, "type").addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
result = dataSnapshot.getValue();
result = result;
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
})
I get: null
.
My Datasnapshot
对象有key = "posts"
and value = null