android - 使用 ArrayAdapter 向 ListView 添加新数据时出错

Question

我正在尝试构建一个简单的聊天应用程序。在聊天对话屏幕中，我使用带有 ArrayAdapter 的 ListView 来存储和显示消息，但是当我接收或发送新消息时，所有最近的消息都会更改为。

这是我的适配器代码:

public class MessageAdapter extends ArrayAdapter<Message> {
    private Context context;
    private ArrayList<Message> messages;
    private DatabaseHelper databaseHelper;
    private Message message;

    @Override
    public void add(Message object) {
        messages.add(object);
        super.add(object);
    }

    public MessageAdapter(Context context, int textViewResouceId, ArrayList<Message> messages) {
        super(context, textViewResouceId);
        this.context = context;
        this.messages = messages;
        databaseHelper = DatabaseHelper.getInstance(context);
    }

    public int getCount() {
        return messages.size();
    }

    public Message getItem(int index) {
        return messages.get(index);
    }

    public long getItemId(int position) {
        return position;
    }

    @Override
    public int getPosition(Message item) {
        return super.getPosition(item);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        MessageViewHolder messageViewHolder;

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.chat_item, parent, false);
            messageViewHolder = new MessageViewHolder();
            messageViewHolder.tv_userName = (TextView) convertView.findViewById(R.id.tv_chatName);
            messageViewHolder.tv_message = (TextView) convertView.findViewById(R.id.tv_messageContent);
            convertView.setTag(messageViewHolder);
        } else {
            messageViewHolder = (MessageViewHolder) convertView.getTag();
        }
        message = messages.get(position);
        String username = databaseHelper.getUserByUserId(message.getUserId()).getUserName();
        if (message.getUserId() == AppConfig.USER_ID) {
            messageViewHolder.tv_message.setTextColor(Color.parseColor("#0066ff"));
            messageViewHolder.tv_userName.setTextColor(Color.parseColor("#0066ff"));
        } else {
            messageViewHolder.tv_message.setTextColor(Color.parseColor("#000000"));
            messageViewHolder.tv_userName.setTextColor(Color.parseColor("#000000"));
        }
        messageViewHolder.tv_userName.setText(username);
        messageViewHolder.tv_message.setText(message.getMessage());

        return convertView;
    }

    static class MessageViewHolder {
        TextView tv_message;
        TextView tv_userName;
    }


}

这是我的 ListView 布局代码:

<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay" />

        </android.support.design.widget.AppBarLayout>

        <ScrollView
            android:id="@+id/scroll_chat"
            android:layout_width="match_parent"
            android:layout_height="380dp">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent">

                <ListView
                    android:id="@+id/listMessage"
                    android:layout_width="match_parent"
                    android:layout_height="380dp"
                    android:background="@null"
                    android:divider="@null"
                    android:stackFromBottom="true"
                    android:drawSelectorOnTop="false"
                    android:transcriptMode="alwaysScroll" />
            </LinearLayout>


        </ScrollView>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal"
            android:weightSum="1">

            <EditText
                android:id="@+id/txt_chat"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_weight="0.92" />

            <Button
                android:id="@+id/btn_send"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_marginLeft="30dp"
                android:text="@string/btn_send" />
        </LinearLayout>
    </LinearLayout>

当我发送两条消息时这是错误(当我收到一条消息时会发生同样的错误)

我认为问题出在将数据设置为 View 的方式，但我无法解决。谁能帮我解决这个问题。

这是我关闭并再次打开 Activity 时的聊天屏幕:它显示了正确的消息。

这是聊天 Activity 代码:

public class ChatActivity extends AppCompatActivity implements View.OnClickListener {
    private Button btn_send;
    private static EditText txt_chat;
    private String registId;
    private Bundle bundle;
    private String chatTitle;
    private MessageSender mgsSender;
    private int userId;
    private DatabaseHelper databaseHelper;
    private TimeUtil timeUtil;
    private MessageAdapter messageAdapter;
    private ListView lv_message;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        if (getSupportActionBar() != null) {
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }
        btn_send = (Button) findViewById(R.id.btn_send);
        txt_chat = (EditText) findViewById(R.id.txt_chat);
        lv_message = (ListView) findViewById(R.id.listMessage);
//        lv_message.setTranscriptMode(ListView.TRANSCRIPT_MODE_ALWAYS_SCROLL);
        timeUtil = new TimeUtil();
        databaseHelper = DatabaseHelper.getInstance(getApplicationContext());
        btn_send.setOnClickListener(this);
        bundle = getIntent().getExtras();
        chatTitle = bundle.getString("titleName");
        if (getIntent().getBundleExtra("INFO") != null) {
            chatTitle = getIntent().getBundleExtra("INFO").getString("name");
            this.setTitle(chatTitle);
        } else {
            this.setTitle(chatTitle);
        }
        registId = bundle.getString("regId");
        userId = databaseHelper.getUser(chatTitle).getUserId();
        List<Message> messages = databaseHelper.getMessges(AppConfig.USER_ID, databaseHelper.getUser(chatTitle).getUserId());
        messageAdapter = new MessageAdapter(getApplicationContext(), R.layout.chat_item, (ArrayList<Message>) messages);
        LocalBroadcastManager.getInstance(this).registerReceiver(onNotice, new IntentFilter("Msg"));
        if (messages.size() > 0) lv_message.setAdapter(messageAdapter);
    }

    private BroadcastReceiver onNotice = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String message = intent.getStringExtra("message");
            try {
                Message messageObj = Message.getInstance();
                messageObj.setMessage(message);
                messageObj.setUserId(userId);
                messageObj.setSender_id(AppConfig.USER_ID);
                messageObj.setExpiresTime(timeUtil.formatDateTime(timeUtil.getCurrentTime()));
                messageAdapter.add(messageObj);
            } catch (ParseException e) {
                e.printStackTrace();
            }
            messageAdapter.notifyDataSetChanged();
        }
    };


    @Override
    public void onBackPressed() {
        super.onBackPressed();
        finish();
    }


    @Override
    protected void onDestroy() {
        LocalBroadcastManager.getInstance(this).unregisterReceiver(onNotice);
        super.onDestroy();
    }


    private static MessageSenderContent createMegContent(String regId, String title) {
        String message = txt_chat.getText().toString();
        MessageSenderContent mgsContent = new MessageSenderContent();
        mgsContent.addRegId(regId);
        mgsContent.createData(title, message);
        return mgsContent;
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn_send:
                String message = txt_chat.getText().toString();
                databaseHelper = DatabaseHelper.getInstance(getApplicationContext());
                mgsSender = new MessageSender();
                new AsyncTask<Void, Void, Void>() {
                    @Override
                    protected Void doInBackground(Void... params) {
                        MessageSenderContent mgsContent = createMegContent(registId, AppConfig.USER_NAME);
                        mgsSender.sendPost(mgsContent);
                        return null;
                    }
                }.execute();
                databaseHelper.addMessage(message, timeUtil.getCurrentTime(), userId, AppConfig.USER_ID);
                txt_chat.setText("");
                try {
                    Message messageObj = Message.getInstance();
                    messageObj.setMessage(message);
                    messageObj.setUserId(AppConfig.USER_ID);
                    messageObj.setSender_id(userId);
                    messageObj.setExpiresTime(timeUtil.formatDateTime(timeUtil.getCurrentTime()));
                    messageAdapter.add(messageObj);
                } catch (ParseException e) {
                    e.printStackTrace();
                }
                messageAdapter.notifyDataSetChanged();
                break;
        }
    }

}

Answer 1

在您的 ChatActivity 中。在 onClickEvent
尝试改变

Message messageObj = Message.getInstance();

到

Message messageObj = new Message();

您可以在 here 中阅读有关单例模式的更多信息