我可以将数据放入Firebase数据库，但是当我想要检索它并将其显示到ListView时，它只显示空白屏幕。
BaseActivity类：
public class BaseActivity extends AppCompatActivity {
@Bean
OttoBus bus;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
bus.register(this);
}
@Override
protected void onDestroy() {
super.onDestroy();
bus.unregister(this);
}
}
HomeActivity类：
@OptionsMenu(R.menu.signout)
@EActivity(R.layout.activity_home)
public class HomeActivity extends BaseActivity {
private static final int LOGIN_REQUEST_CODE = 42;
@ViewById
ListView listView;
@Bean
ConversationAdapter conversationAdapter;
@Bean
UserDao userDao;
@AfterViews
void init() {
// if no user is logged in
if (FirebaseAuth.getInstance().getCurrentUser() == null) {
LoginActivity_.intent(this).startForResult(LOGIN_REQUEST_CODE);
} else {
userDao.init();
}
listView.setAdapter(conversationAdapter);
}
@OnActivityResult(value = LOGIN_REQUEST_CODE)
void loginSucceeded(int resultCode) {
if (resultCode != RESULT_OK) {
return;
}
userDao.init();
conversationAdapter.resetConversationFlow();
}
@Subscribe
public void usersLoaded(UsersLoadedEvent event) {
final FirebaseUser firebaseUser = FirebaseAuth
.getInstance().getCurrentUser();
if (userDao.userExists(firebaseUser.getUid())) {
userDao.setCurrentUser(userDao.getUserById(firebaseUser.getUid()));
} else {
final User user = new User(firebaseUser.getUid(),
firebaseUser.getDisplayName(),
firebaseUser.getPhotoUrl().toString());
userDao.write(user);
userDao.setCurrentUser(user);
}
}
@ItemClick
void listViewItemClicked(Conversation conversation) {
ConversationActivity_.intent(this)
.conversation(conversation)
.start();
}
/**
* When option item with id signOut is clicked.
*/
@OptionsItem
void signOut() {
FirebaseAuth.getInstance().signOut();
// restart this activity after user is logged out because if there is no user we will start
// login activity
final Intent intent = getIntent();
finish();
startActivity(intent);
}
/**
* Called when button with id=fab is clicked.
*/
@Click
void fab() {
CreateConversationActivity_.intent(this).start();
}
}
activity_home.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.nemus.execomchatworkshop.activity.HomeActivity">
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.FloatingActionButton
android:id="@+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:layout_margin="@dimen/large_margin"
android:src="@drawable/ic_add_black_24dp" />
</RelativeLayout>
ConversationItemView类：
@EViewGroup(R.layout.item_view_conversation)
public class ConversationItemView extends LinearLayout {
@ViewById
TextView title;
public ConversationItemView(Context context) {
super(context);
}
public void bind(Conversation conversation) {
title.setText(conversation.getTitle());
}
}
item_view_conversation.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?android:attr/selectableItemBackground">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal">
<ImageView
android:id="@+id/conversationPhoto"
android:layout_width="@dimen/image_large_size"
android:layout_height="@dimen/image_large_size"
android:layout_margin="@dimen/medium_margin" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="@dimen/large_margin"
android:orientation="vertical">
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textColor="@color/primary_text"
android:textSize="@dimen/large_text" />
<TextView
android:id="@+id/conversationPreview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textColor="@color/secondary_text"
android:textSize="@dimen/medium_text" />
</LinearLayout>
</LinearLayout>
</RelativeLayout>
ConversationDao class
@EBean(scope = EBean.Scope.Singleton)
public class ConversationDao {
static final String CONVERSATION_TAG = "conversations";
private FirebaseDatabase database = FirebaseDatabase.getInstance();
private List<Conversation> conversations = new ArrayList<>();
private Map<String, Conversation> conversationMap = new HashMap<>();
@Bean
OttoBus bus;
/**
* After this class is injected call this method.
*/
@AfterInject
public void init() {
database.getReference(CONVERSATION_TAG).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
conversationMap = dataSnapshot.getValue(
new GenericTypeIndicator<Map<String, Conversation>>() {
});
publish();
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
public void write(Conversation conversation) {
final DatabaseReference databaseReference =
database.getReference(CONVERSATION_TAG).push();
conversation.setId(databaseReference.getKey()); // set unique key to our conversation
databaseReference.setValue(conversation); // push conversation to database
}
public List<Conversation> getConversations() {
return conversations;
}
private void publish() {
conversations.clear();
if (conversationMap != null) {
conversations.addAll(conversationMap.values());
}
// post to event bus
bus.post(new ConversationsUpdateEvent());
}
ConversationAdapter类：
@EBean
public class ConversationAdapter extends BaseAdapter {
private List<Conversation> conversations = new ArrayList<>();
@RootContext
Context context;
@Bean
ConversationDao conversationDao;
@Bean
OttoBus bus;
/**
* This method is called after this class is injected.
*/
@AfterInject
void init() {
bus.register(this);
}
public void resetConversationFlow() {
conversationDao.init();
}
@Override
public int getCount() {
return conversations.size();
}
@Override
public Conversation getItem(int position) {
return conversations.get(position);
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final ConversationItemView conversationItemView;
if (convertView == null) { // if view item is not created
conversationItemView = ConversationItemView_.build(context);
} else { // if view item was already created
conversationItemView = (ConversationItemView) convertView;
}
// bind data to view
conversationItemView.bind(getItem(position));
return conversationItemView;
}
private void setConversations(List<Conversation> conversations) {
this.conversations = conversations;
// notify that data set changed so that the list is refreshed
notifyDataSetChanged();
}
@Subscribe
public void conversationsUpdated(ConversationsUpdateEvent event) {
setConversations(conversationDao.getConversations());
}
}
那么，我在这里错过了什么。为什么不在ListView中显示会话标题？
答案 0 :(得分：1)
很难遵循允许一次使用所有这些代码。如果你提出一个小问题而不是一个大问题，你更有可能得到答案。这就是我建议你弄清楚如何解决这个问题：
在您成功检索到数据后，设置断点即可停止。然后确认您确实收到了数据，并且它当前存储在您要使用的变量中。
既然您已确认数据存在，请确保正确设置列表视图。
首先，我建议你从RecylerView开始，因为这是更新的标准，并且有更多有用的在线教程。它们基本上是一回事，但RecylerView更好。然后我将继续使用调试器来检查我的数据是否正确地传递给RecylerViewAdapter，并且当数据有界时，它会将其指向正确的视图。
Here is a good tutorial for using the Android studio debugger.
Here is a good tutorial by google for adding lists(Using recylerview)