收到消息时无法刷新列表视图答案

【问题标题】：Unable to refresh listview on message received收到消息时无法刷新列表视图
【发布时间】：2019-12-21 09:06:47
【问题描述】：

我是 android 开发的新手，我学到的一切都来自教程和 Stack Overflow。我的应用程序已经完成了 90%，但无法刷新从 API JSON 网页中提取的列表视图。

我已经阅读了与我的问题相关的所有文章，我遵循的每个过程要么使应用程序崩溃，要么什么也不做。

这是我的 MainActivity.java

public class MainActivity extends AppCompatActivity {
    private static final String tag = MainActivity.class.getSimpleName();
    private List<DataSet> list = new ArrayList<DataSet>();
    private ListView listView;
    private Adapter adapter;

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.mybutton) {
            Intent intent = new Intent(MainActivity.this, SettingsActivity.class);
            startActivity(intent);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.list);
        adapter = new Adapter(this, list);
        listView.setAdapter(adapter);


        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
        String ipadr = preferences.getString("signature", "0.0.0.0");
        JsonArrayRequest jsonreq = new JsonArrayRequest("http://" + ipadr + "/android.php",
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {

                        for (int i = 0; i < response.length(); i++) {
                            try {

                                JSONObject obj = response.getJSONObject(i);
                                DataSet dataSet = new DataSet();
                                dataSet.setName(obj.getString("resident"));
                                dataSet.setImage(obj.getString("image"));
                                dataSet.setWorth(obj.getString("type"));
                                dataSet.setSource(obj.getString("starttime"));
                                list.add(dataSet);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }

                        }
                        adapter.notifyDataSetChanged();
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                AlertDialog.Builder add = new AlertDialog.Builder(MainActivity.this);
                add.setMessage(error.getMessage()).setCancelable(true);
                AlertDialog alert = add.create();
                alert.setTitle("Error: Unable to connect to Server");
                alert.show();
            }
        });
        Controller.getPermission().addToRequestQueue(jsonreq);
    }
    public class MessageReceiver extends FirebaseMessagingService {
        private static final int REQUEST_CODE = 1;
        private static final int NOTIFICATION_ID = 6578;
        private static final String TAG = "MyFirebaseMsgService";

        public MessageReceiver() {
            super();
        }

        @Override
        public void onMessageReceived(RemoteMessage remoteMessage) {
            super.onMessageReceived(remoteMessage);
            Log.d(TAG, "From: " + remoteMessage.getFrom());
            if (remoteMessage.getNotification() != null) {
                Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
            }
            final String title = remoteMessage.getData().get("title");
            final String message = remoteMessage.getData().get("body");
            finish();
            startActivity(getIntent());
            overridePendingTransition(0, 0);
            showNotifications(title, message);
        }
        private void showNotifications(String title, String msg) {
            Intent i = new Intent(this, MainActivity.class);
            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            String NOTIFICATION_CHANNEL_ID = "my_channel_id_01";

            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "My Notifications", NotificationManager.IMPORTANCE_MAX);

                // Configure the notification channel.
                notificationChannel.setDescription("Channel description");
                notificationChannel.enableLights(true);
                notificationChannel.setLightColor(Color.RED);
                notificationChannel.setVibrationPattern(new long[]{0, 1000, 500, 1000});
                notificationChannel.enableVibration(true);
                notificationManager.createNotificationChannel(notificationChannel);
            }


            NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);

            notificationBuilder.setAutoCancel(true)
                    .setDefaults(Notification.DEFAULT_ALL)
                    .setWhen(System.currentTimeMillis())
                    .setSmallIcon(R.drawable.rnifyround)
                    .setTicker("Hearty365")
                    //     .setPriority(Notification.PRIORITY_MAX)
                    .setContentTitle(title)
                    .setContentText(msg)
                    .setContentInfo("Info");

            notificationManager.notify(/*notification id*/1, notificationBuilder.build());
        }
    }
}

我的 JSON 输出示例

[{"image":"http://1.2.3.4/images/check.png","starttime":"2019-08-06 20:43:06","endtime":"2019-08-06 20:43:19","serial":"11298293","type":"Pendant","resident":"Resident Name","room":"APT 200","bed":"1","state":"closed"},{"image":"http://1.2.3.4/images/check.png","starttime":"2019-08-05 20:39:26","endtime":"2019-08-05 20:39:39","serial":"11298293","type":"Pendant","resident":"Resident Name","room":"APT 200","bed":"1","state":"closed"}]

我希望在收到通知并且应用程序处于前台时刷新我的列表视图。我还需要让它在滑动时刷新，但我仍在努力。

编辑

public class Adapter extends BaseAdapter {

    private Activity activity;
    private LayoutInflater inflater;
    private List<DataSet> DataList;
    ImageLoader imageLoader = Controller.getPermission().getImageLoader();

    public Adapter(Activity activity, List<DataSet> dataitem) {
        this.activity = activity;
        this.DataList = dataitem;
    }

    @Override
    public int getCount() {
        return DataList.size();
    }

    @Override
    public Object getItem(int location) {
        return DataList.get(location);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (inflater == null)
            inflater = (LayoutInflater) activity
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null)
            convertView = inflater.inflate(R.layout.listview, null);

        if (imageLoader == null)
            imageLoader = Controller.getPermission().getImageLoader();
        NetworkImageView thumbNail = (NetworkImageView) convertView
                .findViewById(R.id.thumbnail);
        TextView name = (TextView) convertView.findViewById(R.id.name);
        TextView worth = (TextView) convertView.findViewById(R.id.worth);
        TextView source = (TextView) convertView.findViewById(R.id.source);
        DataSet m = DataList.get(position);
        thumbNail.setImageUrl(m.getImage(), imageLoader);
        name.setText("Resdient: " + (m.getName()));
        source.setText("Activated: " + (m.getSource()));
        worth.setText("Call Type: " + (m.getWorth()));

        return convertView;
    }

}

【问题讨论】：

我会看看广播，这是让您的应用知道发生了什么事的好方法。您可以订阅关于您的活动 onResume 的广播，并在您离开活动时取消订阅（onStop/onPause）。并在收到正确类型的广播时更新您的适配器。你可以在这里阅读更多关于它们的信息：developer.android.com/guide/components/broadcasts
你能告诉我们你的适配器吗？
我会看看广播。我已经更新了 Adapter.java。
@urukh 我能够让它与广播一起工作，所以谢谢。我正在做的一件事是将我的整个代码从我的 onCreate 方法复制到我的其他方法中以进行刷新。有没有更好的办法？
@MattSaiko 因为您的适配器与 var "list" 链接，您可以创建一个仅更新此列表的方法，然后调用 notifyDatasetChanged，无需每次都重新创建实例。我还建议将您的代码分解为更小的方法，这会使事情更容易理解和维护

标签： android listview android-activity

【解决方案1】：

我认为您应该创建refresh() {contain your codes: fetch data, add to list and notifyDataSetChange} 函数并在onCreate() 和onMessageReceived() 中调用它，并且不要完成并重新启动活动

【讨论】：

【解决方案2】：

感谢@urukh，我能够通过广播完成这项工作。

在我的 MessageReciever Activity showMessage 方法中，我调用我的方法sendMessage();

sendMessage 方法

private void sendMessage() {
        Log.d("sender", "Broadcasting message");
        Intent intent = new Intent("custom-event-name");
        // You can also include some extra data.
        intent.putExtra("message", "This is my message!");
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
    }

然后在我的 MainActivity 中

private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
        //Code to refresh listview
    }
}

【讨论】：