如何在实时数据库中检查值(打开/关闭) [英] How to check value in realtime database (ON/OFF)

问题描述

我如何使用此代码

    @Override
protected void onStart() {
    super.onStart();
    //if the user is already signed in
    //we will close this activity
    //and take the user to profile activity
    if (mAuth.getCurrentUser() != null) {
        finish();
        startActivity(new Intent(this, ActivitySplash.class));
    }

}

检查子代(userId)是否设置为ON/OFF，如果为ON，则运行代码

make check whether the child (userId) is set to ON / OFF and if ON then we run the code

    if (mAuth.getCurrentUser() != null) {
    finish();
    startActivity(new Intent(this, ActivitySplash.class));
}

如果关闭，则显示特定活动.

if OFF then we show a specific activity.

我的数据库

推荐答案

正如@FrankvanPuffelen所说，您应该花一些时间阅读文档，这将有助于您自己编写代码，但我还是在这里为您简要介绍一下.它应该使事情更清楚.

As @FrankvanPuffelen said, you should spend some time reading docs, it would help you write code yourself, still I am briefing the things for you here. It should make things more clear.

通过从数据库中正确引用所需的节点，然后使用正确的eventListener来完成从数据库的读取. eventListeners存在3种类型，singleValueEventListener，valueEventListener和childEventListener.

Reading from database is done by correctly referencing your desired node from the database and then using the correct eventListener. There are 3 types of eventListeners present, singleValueEventListener, valueEventListener and childEventListener.

在文档中详细了解它们的更多信息. 此答案还可以帮助您理解childEventListeners.

Read more about each of them in detail in docs. This answer can also help you understand childEventListeners.

要检索status节点的值，必须依次遍历数据库父节点，这些父节点是users且值为nfe...的uid.

To retrieve the value of status node you have to go sequentially through your database parent nodes, that are users and that uid with value nfe....

所以在代码中看起来像这样:

So in code it would look something like this:

DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("users").child(uid);

// uid has the value nfe...


ref.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String status = dataSnapshot.child("status").getValue(String.class);
             // compare the value of status here and do what you want    
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Log.d(TAG, "onCancelled", databaseError.toException());
            }


        });

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