更新:我已经决定重新提出问题,以便更好地澄清问题并使用更专注的代码。
我遇到的问题是我有一个UserList对象的ArrayList,它是上一个活动中的选定用户,我们称之为selectedUsers
。我有另一个对象,我想将selectedUsers
以及Firebase中的当前用户分组。这将被称为mGroupMembers
,它包含GroupMember对象。
我能够将selectedUsers
放入mGroupMembers
的ArrayList中,但我无法将当前用户(由其ID引用)放入所述ArrayList中。我认为问题在于Firebase。我不确定为什么当我拨打addListenerForSingleValueEvent
时,当前用户的数据没有添加到mGroupMembers
ArrayList?
这是我的代码:
public class TestActivity extends AppCompatActivity {
//Tag
private static String TAG = "TestActivity";
private List<UserList> selectedUsers;
private TextView mPickedText;
private TextView mCurrentText;
private TextView mMembCountText;
private List<GroupMembers> mGroupMembers;
private String memberNames;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
//Selected users from previous activity.
selectedUsers = (List<UserList>) getIntent().getSerializableExtra("users");
//Text Views
mPickedText = (TextView) findViewById(R.id.first_text);
mCurrentText = (TextView) findViewById(R.id.second_text);
mMembCountText = (TextView) findViewById(R.id.third_text);
//GroupMembs
mGroupMembers = new ArrayList<>();
//Current user.
final String currentUserID = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference mRef = FirebaseDatabase.getInstance().getReference().child("users").child(currentUserID);
mRef.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
UserList user = dataSnapshot.getValue(UserList.class);
GroupMembers member;
//If the current user...
if (Objects.equals(user.getUid(), currentUserID)) {
mCurrentText.setText("Current: " + user.getName());
member = new GroupMembers(user.getName(), user.getUsername(), user.getEmail(), user.getUid());
Log.d(TAG, "Member object contains...Name: " + user.getName() + "\n" +
"Username: " + user.getUsername() + "\n" +
"Email: " + user.getEmail() +
"uid: " + user.getUid());
selectedUsers.add(user);
mGroupMembers.add(member);
for (GroupMembers members : mGroupMembers) {
Log.d(TAG, "Member object contains...Name: " + members.getName() + "\n" +
"Username: " + members.getUsername() + "\n" +
"Email: " + members.getEmail() +
"uid: " + members.getUid());
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
//Picked user.
for (UserList selected : selectedUsers) {
GroupMembers member = new GroupMembers();
member.setName(selected.getName());
member.setUsername(selected.getUsername());
member.setEmail(selected.getEmail());
member.setUid(selected.getUid());
mGroupMembers.add(member);
mPickedText.setText("Selected: " + selected.getName());
}
for (GroupMembers members : mGroupMembers) {
memberNames = members.getName();
}
mMembCountText.setText("Group Members: " + mGroupMembers.size() + " ");
}
}
这是Firebase数据库
{
"users" : {
"S3l3yRh8TqRYNeTWQ7tKEdUe2K03" : {
"email" : "antwon@domain.com",
"name" : "Antwon ",
"profilePicture" : " ",
"uid" : "S3l3yRh8TqRYNeTWQ7tKEdUe2K03",
"username" : "ant01"
},
"af7KgxP7QgZT3d6adtgwBRwnsaI2" : {
"email" : "bill@domain.com",
"name" : "Bill",
"profilePicture" : " ",
"uid" : "af7KgxP7QgZT3d6adtgwBRwnsaI2",
"username" : "Bill123"
}
}
}
这是我记录mGroupMembers
ArrayList:
D/TestActivity: Member object contains...Name: Antwon
Username: ant01
Email: antwon@domain.comuid: S3l3yRh8TqRYNeTWQ7tKEdUe2K03
D/TestActivity: Member object contains...Name: Bill
Username: Bill123
Email: bill@domain.comuid: af7KgxP7QgZT3d6adtgwBRwnsaI2
D/TestActivity: Member object contains...Name: Antwon
Username: ant01
Email: antwon@domain.comuid: S3l3yRh8TqRYNeTWQ7tKEdUe2K03
正在添加当前用户(Antwon),但为什么在运行程序时不显示?现在,程序只显示所选用户的姓名以及当前用户的姓名。然后它显示mGroupMembers
的大小。当然,当它应该是两个时,它的大小只有1个。
答案 0 :(得分:1)
意外行为是Firebase侦听器异步性质的结果。在从Firebase服务器检索数据快照之前,getUserInfo
不会执行。这通常需要几毫秒,并且将在添加侦听器之后的语句之后发生。对于您的代码,在onDataChange()触发并添加当前用户之前执行此for语句:
onDataChange()
this answer中提供了对Firebase异步数据加载的进一步说明。