安卓系统:更新数据集，其中数据集是HashMaps的ArrayList

Question

我最近开始从事一个Android项目，由于我对UI编程缺乏了解，当我试图动态地向UI添加条目时，我发现自己陷入了困境。

我正在开发一个聊天应用程序，当收到新消息时，应该在底部添加它。为此，我需要通知数据集已经更改。当我直接调用数据集更改时，我得到了一个错误。所以我在适配器上使用了本地广播接收器。

不幸的是，我不知道如何传递包含HashMap的ArrayList。我将发布适配器的代码，以及我试图通知数据更改的位置。我希望有人能帮我。THanks很多..：-）

代码：

    public static void recieveUpdatedMessage(String channelName, Map<String, Object> input){
//The input here contains message from our PUSH system 
  Intent intent = new Intent();
                    HashMap<String, String> insertMap = new HashMap<>();
                    insertMap.put(chatText, String.valueOf(input.get("text")));
                    insertMap.put(firstName,String.valueOf("firstname"));
                    insertMap.put(groupChannel, "/service/chat" + String.valueOf(groupAccountId));
                    ArrayList<HashMap<String, String>> chatMessagesHashMapList = new ArrayList<HashMap<String, String>>();
                    chatMessagesHashMapList.add(insertMap);
// Below is where I am trying to send data.
                 //  intent.putExtra(chatMessagesHashMapList);//send any data to your adapter
                    intent.setAction("myaction");
                    LocalBroadcastManager.getInstance(context).sendBroadcast(intent);

适配器代码，它在同一个java文件中：

public class ChatMessagesAdapter extends BaseAdapter {

private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent)
    {
        if(intent.getAction().equals("MYREFRESH"))
        {
            notifyDataSetChanged();
        }
    }
};
    private Activity activity = null;
    private ArrayList<HashMap<String, String>> data;
    private LayoutInflater inflater = null;

    public ChatMessagesAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("MYREFRESH");
        LocalBroadcastManager.getInstance(context).registerReceiver(broadcastReceiver, intentFilter);
        activity = a;
        data = d;
        inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }
    @Override
    public int getCount() {
        return data.size();
    }
    @Override
    public Object getItem(int position) {
        return position;
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View vi = convertView;
        if (convertView == null)
            vi = inflater.inflate(R.layout.chat_messages_row, parent, false);
        TextView chatText = (TextView) vi.findViewById(R.id.chatText);
        ImageView userImage = (ImageView) vi.findViewById(R.id.chatImage);
        TextView firstName = (TextView) vi.findViewById(R.id.personName);
        HashMap<String, String> chatList = new HashMap<>();
        chatList = data.get(position);
        chatText.setText(chatList.get(ChatMessagesActivity.chatText));
        userImage.setImageBitmap(convertByteArrayToBitmap(chatList.get(ChatMessagesActivity.chatImage)));
        firstName.setText(chatList.get(ChatMessagesActivity.firstName));
        return vi;
    }
}

我希望我是清白的。如果有什么遗漏，请告诉我。我如何告诉活动有新消息并将其放在底部。

Answer 1

您真的不应该那样使用BroadcastReceiver。尝试将add方法添加到Adapter中，以便更容易地添加项目并自动通知更改。

public void add(HashMap<String, String> item) {
    data.add(item);
    notifyDataSetChanged();
}

然后，在recieveUpdatedMessage方法中，您可以执行与以下类似的操作。

public void recieveUpdatedMessage(String channelName, Map<String, Object> input) {
    HashMap<String, String> insertMap = new HashMap<>();
    insertMap.put(chatText, input.get("text").toString());
    insertMap.put(firstName, input.get("firstname").toString());
    insertMap.put(groupChannel, "/service/chat" + input.get("groupaccountid").toString());
    myAdapter.add(insertMap);
}

需要改进的几个注意事项

与其使用HashMap，不如创建一个类来为您保存数据。

由于您的BaseAdapter已经在使用List，您可以扩展ArrayAdapter，因为它已经有一个默认情况下也调用notifyDataSetChanged()的add方法。

Answer 2

在使用HashMap创建数据的情况下，您可以使用bundle将最新数据直接传递到intent中&从BroadCastReceiver 的onReceive方法中检索

如何传递数据检查下面的更新方法recieveUpdatedMessagereceiveUpdatedMessage

public static void recieveUpdatedMessage(String channelName, Map<String, Object> input) {
//The input here contains message from our PUSH system
        Intent intent = new Intent();
        HashMap<String, String> insertMap = new HashMap<>();
        insertMap.put(chatText, String.valueOf(input.get("text")));
        insertMap.put(firstName, String.valueOf("firstname"));
        insertMap.put(groupChannel, "/service/chat" + String.valueOf(groupAccountId));
        ArrayList<HashMap<String, String>> chatMessagesHashMapList = new ArrayList<HashMap<String, String>>();
        // Added your map into Bundler as a Serializable
        Bundle bundle = new Bundle();
        bundle.putSerializable("chatMapKey", insertMap);
//        after adding map into bundle . bundle is added into Intent
        intent.putExtras(bundle);
// Below is where I am trying to send data.
        //  intent.putExtra(chatMessagesHashMapList);//send any data to your adapter
        intent.setAction("MYREFRESH");
        LocalBroadcastManager.getInstance(context).sendBroadcast(intent);
    }

如何从bundle&在listview中更新它检查您的ChatMessagesAdapter更新代码。

聊天消息适配器

public class ChatMessagesAdapter extends BaseAdapter {

        private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                if (intent.getAction().equals("MYREFRESH")) {
                    Bundle bundle = intent.getExtras();
                    // Get the bundle from intent
                    if (bundle!=null && bundle.containsKey("chatMapKey")) {
//                        get the Serializable object which is pass as a broadcast from the Bundle
                        refreshChat((HashMap<String, String>) bundle.getSerializable("chatMapKey"));
                    }
                }
            }
        };
        private Activity activity = null;
        private ArrayList<HashMap<String, String>> data;
        private LayoutInflater inflater = null;
        private int size = 0;
        public ChatMessagesAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
            IntentFilter intentFilter = new IntentFilter();
            intentFilter.addAction("MYREFRESH");
            LocalBroadcastManager.getInstance(context).registerReceiver(broadcastReceiver, intentFilter);
            activity = a;
            data = d;
            if (data != null)
                size = data.size();
            inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }
        public void refreshChat(HashMap<String, String> newChatMap) {
            if (data == null) {// Added Condition for safe side you can remove it
                data = new ArrayList<HashMap<String, String>>();
            }
            data.add(newChatMap);
            size = data.size();
            notifyDataSetChanged();
        }
        @Override
        public int getCount() {
            return size;
        }
        @Override
        public Object getItem(int position) {
            return position;
        }
        @Override
        public long getItemId(int position) {
            return position;
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            View vi = convertView;
            if (convertView == null)
                vi = inflater.inflate(R.layout.chat_messages_row, parent, false);
            TextView chatText = (TextView) vi.findViewById(R.id.chatText);
            ImageView userImage = (ImageView) vi.findViewById(R.id.chatImage);
            TextView firstName = (TextView) vi.findViewById(R.id.personName);
            HashMap<String, String> chatList = new HashMap<>();
            chatList = data.get(position);
            chatText.setText(chatList.get(ChatMessagesActivity.chatText));
            userImage.setImageBitmap(convertByteArrayToBitmap(chatList.get(ChatMessagesActivity.chatImage)));
            firstName.setText(chatList.get(ChatMessagesActivity.firstName));
            return vi;
        }
    }

建议

• 避免像以前那样使用广播接收器。在中注册活动onReusme/onStart&在其onPause/onStop中注销方法检查可见寿命

• 尝试像在发送消息时那样使用数据库维护数据接收将其插入数据库&在刷新数据时获取来自数据库的数据