java - 从服务类向 Sqlite 添加数据时 Recyclerview 不更新？

Question

在这里，我尝试将数据从firebase数据库保存到sqlite数据库中，并成功保存。并且当添加新数据时，Sqlite数据库会定期更新。但问题是只有当 Activity 重新启动时才会出现新数据。Recyclerview 在恢复 Activity 之前不会更新。这是我的服务类别。

      public class NetworkBroadcast  extends Service
    {
        public int onStartCommand(Intent intent, int flags, int startId)
        {
            FirebaseAuth mAuth=FirebaseAuth.getInstance();
            checkNewMessage(mAuth);
        }
private void checkNewMessage(final FirebaseAuth mAuth)
    {
        final String CurrentUID=mAuth.getCurrentUser().getUid();
        final DatabaseReference MessageRef= FirebaseDatabase.getInstance().getReference().child("Messages").child(CurrentUID);
        final DatabaseReference MessageSenderRef= FirebaseDatabase.getInstance().getReference().child("Messages");
        MessageRef.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
            {

                final String SenderKey=dataSnapshot.getKey();
                Log.i("SERVER_MESSAGE",SenderKey);
                final MyDbHandler myDbHandler=new MyDbHandler(NetworkBroadcast.this,SenderKey+".db",null,1);
                final MessagesAdapter messagesAdapter=new MessagesAdapter(myDbHandler.sqlMessagesList(),NetworkBroadcast.this,SenderKey,myDbHandler);
                MessageRef.child(SenderKey).addChildEventListener(new ChildEventListener()
                {
                    @Override
                    public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
                    {

                            Messages messages=dataSnapshot.getValue(Messages.class);
                            String pushKey=dataSnapshot.getKey();
                            checkDatabaseHasMessageOrNotWithStatus(messages,pushKey,messagesAdapter,myDbHandler);
                            checkMessageStatus(messages,CurrentUID,SenderKey,myDbHandler);
                            chnageSenderMessageStatus(messages,CurrentUID,MessageSenderRef);
                        messagesAdapter.updateData(myDbHandler.sqlMessagesList());
                    }

                    @Override
                    public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s)
                    {

                        Messages statusmessage=dataSnapshot.getValue(Messages.class);
                        String key=dataSnapshot.getKey();

                        boolean update=myDbHandler.upDateDataBaseForStatus(statusmessage.getStatus(),key);
                        if (update=true)
                        {
                            Log.i("SERVER_MESSAGE","my message is update");
                        }

                    }

                });
            }

        });
    }
    }

适配器类构造函数是

public MessagesAdapter(List<SqlMessages> userMessagesList, Context mContext, String messageReceiverId, MyDbHandler myDbHandler)
    {
        this.userMessagesList = userMessagesList;
        this.mContext = mContext;
        ReceiverID=messageReceiverId;
        this. myDbHandler=myDbHandler;

    } 
public void updateData(List<SqlMessages> sqlMessages)
    {
        this.userMessagesList=sqlMessages;
        notifyDataSetChanged();
    }

Answer 1

首先，您需要定义您的 Activity，类似于以下代码。请注意此代码更新其适配器的方式。

public class MainActivity extends AppCompatActivity {
    MessagesAdapter adapter;
    Recyclerview recycler;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    List<SqlMessages> list=new ArrayList();
    adapter=new MessagesAdapter(list);
    recycler=findViewById(R.id.recycler);
    recycler.setLayoutManager(new LayoutManager());
    recycler.setAdapter(adapter);
}

    @Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    final List<SqlMessages> list=data.getSomeData();
    MainActivity.this.runOnUiThread(new Runnable() {
        @Override
        public void run() {
            adapter.updateData(list);
        }
    });
}
}

您应该重写您的适配器，使其看起来像这样的代码。记住notifyDataSetChanged必须从UiThread调用。

public class MessagesAdapter extends RecyclerView.Adapter<YourViewHolderClass> {
List<SqlMessages> userMessagesList;
Context mContext;
MyDbHandler  myDbHandler;
String ReceiverID;

public MessagesAdapter(List<SqlMessages> userMessagesList, Context mContext, String messageReceiverId, MyDbHandler myDbHandler){
    this.userMessagesList = userMessagesList;
    this.mContext = mContext;
    ReceiverID=messageReceiverId;
    this. myDbHandler=myDbHandler;
}

@Override
public YourViewHolderClass onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(someLayout, parent, false);
    return new YourViewHolderClass(view);
}

@Override
public void onBindViewHolder(final YourViewHolderClass holder, int position) {
    holder.setSomething(userMessagesList.get(position).getSomething());
    holder.setAnotherThing(userMessagesList.get(position).getAnotherThing())
}

@Override
public int getItemCount() {
    return list.size();
}

public void updateData(List<SqlMessages> sqlMessages){
    this.userMessagesList=sqlMessages;
    notifyDataSetChanged();
}
}

你的ViewHolderClass看起来像这样

public class YourViewHolderClass  extends RecyclerView.ViewHolder {

TextView textView;
TextView textView1;

public YourViewHolderClass(@NonNull View itemView) {
    super(itemView);
    textView = itemView.findViewById(R.id.text);
    textView1 = itemView.findViewById(R.id.text1);
}

public void setSomething(String x) {
    this.textView.setText(x);
}
public void setAnotherthing(String x) {
    this.textView1.setText(x);
}
}

在 someLayout 中，您必须定义一个 CardView 项。类似于下面的代码

<androidx.cardview.widget.CardViewxmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view"
android:layout_width="120dp"
android:layout_height="wrap_content"
card_view:cardCornerRadius="4dp">

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical"
    android:padding="0dp">

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/text1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>
</androidx.cardview.widget.CardView>