java - Firebase 查询方法不起作用

Question

这是我的数据树:

"look-twopointo": {
    "0" {
        "comment": "Hi"
        "Text1": "Hello"
        "Text2": "Bonsoir"
        "type": "Bonjour"
        "version": "4.0.6"
    }
}

由于某种原因，查询不起作用。

button.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        mDatabase = FirebaseDatabase.getInstance().getReference().child("0");// pay attention to the this path reference
        // Read from the database
        Query query = mDatabase.child("version")/*.orderByChild("Text1")*/.equalTo("4.0.6")/*.startAt("d")/*.endAt("Dude")*/;
        query.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.
                //String value = dataSnapshot.getValue(String.class); //these three lines below are probably the problem
                String value = (String) dataSnapshot.getValue();
                System.out.println(value);
                Text.setText(value);
            }

以下是系统输出的内容:

D/ViewRootImpl: ViewPostImeInputStage processPointer 0
D/ViewRootImpl: ViewPostImeInputStage processPointer 1
I/DynamiteModule: Considering local module 
com.google.android.gms.firebase_database:4 and remote module 
com.google.android.gms.firebase_database:6
              Selected remote version of 
com.google.android.gms.firebase_database, version >= 6
D/ResourcesManager: For user 0 new overlays fetched Null
W/System: ClassLoader referenced unknown path: 
/data/data/com.google.android.gms/app_chimera/m/0000005e/n/armeabi-v7a
      ClassLoader referenced unknown path: 
/data/data/com.google.android.gms/app_chimera/m/0000005e/n/armeabi
D/ResourcesManager: For user 0 new overlays fetched Null
I/System.out: null

不知道是不是因为我用的是手机，没有下载并在模拟器上试用。我需要设置什么才能在手机上查询吗？

这可能是导致此问题的错误

05-28 17:12:42.743 2449-3078/? E/NetlinkEvent: NetlinkEvent::FindParam(): Parameter 'LABEL' not found
NetlinkEvent::FindParam(): Parameter 'UID' not found

或者我就是这样

W/System: ClassLoader referenced unknown path: 
/data/data/com.google.android.gms/app_chimera/m/0000005e/n/armeabi-v7a
          ClassLoader referenced unknown path: 
/data/data/com.google.android.gms/app_chimera/m/0000005e/n/armeabi

我希望它输出 4.0.6。

更新:我实际上找不到错误。它无缘无故地输出 null

Answer 1

要解决此问题，您需要将查询更改为:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRef.orderByChild("version").equalTo("4.0.6");

并且将返回所有 version 属性等于 4.0.6 的记录。