Question

这是我的问题。

我最近刚开始使用android，并且想建立一个即时通讯工具。

我使用listview显示聊天记录但未能将新消息添加到listview中。如果有人可以，请帮忙。

这是代码：

XML

<ListView
android:id="@+id/list"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_above="@id/bottom_write_bar"
android:layout_alignParentTop="true"
android:cacheColorHint="#00000000"
android:divider="#00000000"
android:listSelector="#00000000" >
</ListView>

爪哇

public class MessageActivity extends Activity {

    private EditText messageText;
    private ListView historyList;
    private Button sendButton;
    private AppManager appService;
    private FriendInfo friend = new FriendInfo();
    private LocalDataHandler localDataHandler;
    private Cursor dbCursor;
    private MessageAdapter adapter;

    private ArrayList<Message> messages = new ArrayList<Message>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_message);

        historyList = (ListView) findViewById(R.id.list);
        messageText = (EditText) findViewById(R.id.messageText);
        sendButton = (Button) findViewById(R.id.sendButton);

        adapter = new MessageAdapter(this, messages);
        historyList.setAdapter(adapter);

        Bundle extras = this.getIntent().getExtras();
        String msg = extras.getString(MessageInfo.MESSAGETEXT);
        setTitle("Messaging with " + friend.userName);

        localDataHandler = new LocalDataHandler(this);

        dbCursor = localDataHandler.get(friend.userName, AppService.USERNAME);
        if (dbCursor.getCount() > 0) {
            int scorer = 0;
            dbCursor.moveToFirst();
            while ((!dbCursor.isAfterLast()) && scorer < dbCursor.getCount()) {
                scorer++;
                this.addToHistory(dbCursor.getString(2), dbCursor.getString(3));
                //Log.i("test", "Sending text " + dbCursor.getString(2) + " to " + dbCursor.getString(3));
                dbCursor.moveToNext();
            }
        }
        localDataHandler.close();


        if (msg != null) {
            this.addToHistory(friend.userName, msg);
            ((NotificationManager) getSystemService(NOTIFICATION_SERVICE)).cancel((friend.userName + msg).hashCode());
        }
        //checkMsg(msg);

        sendButton.setOnClickListener(new OnClickListener() {
            CharSequence message;
            Handler handler = new Handler();

            public void onClick(View arg0) {
                message = messageText.getText();
                if (message.length() > 0) {
                    MessageActivity.this.addToHistory(appService.getUsername(), message.toString());

                    localDataHandler.insert(appService.getUsername(), friend.userName, message.toString());

                    messageText.setText("");
                    Thread thread = new Thread() {
                        public void run() {
                            try {
                                if (appService.sendMessage(appService.getUsername(), friend.userName, message.toString()) == null) {

                                    handler.post(new Runnable() {

                                        public void run() {

                                            Toast.makeText(getApplicationContext(), R.string.message_cannot_be_sent, Toast.LENGTH_LONG).show();


                                            //showDialog(MESSAGE_CANNOT_BE_SENT);
                                        }

                                    });
                                }
                            } catch (UnsupportedEncodingException e) {
                                Toast.makeText(getApplicationContext(), R.string.message_cannot_be_sent, Toast.LENGTH_LONG).show();

                                e.printStackTrace();
                            }
                        }
                    };
                    thread.start();

                }

            }
        });
    }

    private void addToHistory(String name, String message) {
        if (name != null && message != null) {
            if (name == friend.userName) {
                messages.add(new Message(message, false));
                adapter.notifyDataSetChanged();
                historyList.setSelection(messages.size() - 1);
            } else {
                messages.add(new Message(message, true));
                historyList.addFooterView(messageText);
                adapter.notifyDataSetChanged();
                historyList.setSelection(messages.size() - 1);
            }
        }
    }
}

MessageAdapter

      private Context mContext;
private ArrayList<Message> mMessages;

public MessageAdapter(Context context, ArrayList<Message> messages) {
    super();
    this.mContext = context;
    this.mMessages = messages;
}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return mMessages.size();
}

@Override
public Object getItem(int position) {
    // TODO Auto-generated method stub
    return mMessages.get(position);
}

@Override
public long getItemId(int arg0) {
    // TODO Auto-generated method stub
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    Message message = (Message) this.getItem(position);

    ViewHolder holder; 
    if(convertView == null)
    {
            holder = new ViewHolder();
            convertView = LayoutInflater.from(mContext).inflate(R.layout.activity_message_adapter, parent, false);
            holder.message = (TextView) convertView.findViewById(R.id.message_text);
            convertView.setTag(holder);
    }
    else
            holder = (ViewHolder) convertView.getTag();

    holder.message.setText(message.getMessage());

    LayoutParams lp = (LayoutParams) holder.message.getLayoutParams();
    //check if it is a status message then remove background, and change text color.
    if(message.isStatusMessage())
    {
            holder.message.setBackgroundDrawable(null);
            lp.gravity = Gravity.LEFT;
            holder.message.setTextColor(R.color.textFieldColor);
    }
    else
    {                
            //Check whether message is mine to show green background and align to right
            if(message.isMine())
            {
                    holder.message.setBackgroundResource(R.drawable.speech_bubble_green);
                    lp.gravity = Gravity.RIGHT;
            }
            //If not mine then it is from sender to show orange background and align to left
            else
            {
                    holder.message.setBackgroundResource(R.drawable.speech_bubble_orange);
                    lp.gravity = Gravity.LEFT;
            }
            holder.message.setLayoutParams(lp);
            holder.message.setTextColor(R.color.textColor);        
    }
    return convertView;
}
private static class ViewHolder
{
    TextView message;
}

Answer 1

要添加到ListView，您需要添加到附加到它的适配器。例如，在您的情况下，而不是执行以下操作：

messages.add(new Message(message, false));
adapter.notifyDataSetChanged();

你会想要这样做：

adapter.add(new Message(message, false));
adapter.notifyDataSetChanged();

Answer 2

MessageAdapter应该扩展像ArrayAdapter这样的适配器。在MessageAdapter中，确保通过调用public ArrayAdapter (Context context, int resource, List objects)构造函数将ArrayList<Message> messages传递给父级。

使用自定义适配器将新视图添加到列表视图

2 个答案: