java.lang.RuntimeException：布局不能为null

Question

我正在学习this教程，我遇到了一些问题。我能够启动我的应用并与Firebase数据库共享消息;但是，我无法看到它们。但是现在，我收到了这个错误。

  

java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.furka.findit / com.example.furka.findit.ChatActivity}：java.lang.RuntimeException：Layout不能为null。调用setLayout。

这是发送消息按钮的onClick viewListener：

public void onClick(View view) {
                EditText input = (EditText)findViewById(R.id.input);

                // Read the input field and push a new instance
                // of ChatMessage to the Firebase database
                FirebaseDatabase.getInstance()
                        .getReference()
                        .push()
                        .setValue(new ChatMessage(input.getText().toString(),
                                FirebaseAuth.getInstance()
                                        .getCurrentUser()
                                        .getEmail())
                        );
                input.setText("");

这是观看的方法。

private void displayChatMessages() {
        ListView listOfMessages = (ListView)findViewById(R.id.list_of_messages);
        FirebaseListOptions<ChatMessage> options = new FirebaseListOptions.Builder<ChatMessage>()
                .setQuery(query, ChatMessage.class)
                .build();

        adapter = new FirebaseListAdapter<ChatMessage>(options) {
            @Override
            protected void populateView(View v, ChatMessage model, int position) {
                // Get references to the views of message.xml
                TextView messageText = (TextView)v.findViewById(R.id.message_text);
                TextView messageUser = (TextView)v.findViewById(R.id.message_user);
                TextView messageTime = (TextView)v.findViewById(R.id.message_time);

                // Set their text
                messageText.setText(model.getMessageText());
                messageUser.setText(model.getMessageUser());

                // Format the date before showing it
                messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",
                        model.getMessageTime()));
            }
        };

        listOfMessages.setAdapter(adapter);
    }