Firebase Currentuser null，如何使用户登录所有活动

Question

我正在制作一个博客应用程序，注册效果很好，在成功时，在有userprofileactitive开始的新意图时，我在此活动中添加了一个按钮来编写帖子(打开A填充的新活动(是：当前使用者对除注册外的所有活动中都是无效的，这是否与打开新活动后调用函数饰面((有关吗？您能否向我解释如何保持用户登录？

/*after successful registration,the profile activity starts, here's what inside the oncreate methode*/
fabAddClasseP.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent addPostIntent = new Intent(ProfileActivity.this, addPostActivity.class);
                startActivity(addPostIntent);

        }
    });

/* the addPostActivity*/
/* declaration*/
    private FirebaseAuth auth;
/*a reference to the post*/
    private DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("dataPost");
/*a refernce to the user/author of post*/
    private DatabaseReference mDatabaseUser = FirebaseDatabase.getInstance().getReference().child("dataUser");
//then below on the onCreate methode, i make sure all edit texts are filled, 
buttonSavePost.setOnClickListener(new View.OnClickListener() {
//if  all filds are not empty
String PostId = mDatabase.child("PostId").push().getKey();

 //getting the current user id if not null
String userId = auth.getCurrentUser().getUid();


                       writeNewDataPost( userId, PostId, titlePost, contentPost);

    private void writeNewDataPost(String user_id,String post_id, String title, String content) {
        DataPost dataP = new DataPost(title,  content);
            mDatabase.child(Post_id).setValue(dataP);
/*adding a 
node to the current post "author, and setting its value to the current logged in user*/    
    mDatabase.child(post_id).child("author").setValue(user_id);
               }
        }

Answer 1

将当前的用户ID进入其他活动使用此代码

FirebaseUser currentFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
String userId =currentFirebaseUser.getUid();