我已经尝试过我的代码。我正在编写一个聊天应用程序。我的应用程序包含两个活动。第一个活动有一个列表视图，其中每行包含为用户发送的最后一条消息，而第二个活动包含整个对话。在我的应用程序中，我使用了 Android 版的 socket.io。我的应用程序运行良好。
收到数据时列表视图会刷新，但是当我按后退按钮然后返回活动时，列表视图尚未刷新自身。在日志控制台中，我看到数据已收到并调用了“更改”方法，但列表视图未刷新。
下面的代码有什么问题？
package com.example.seadog.fb_dialog;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Typeface;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.TextView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.net.URISyntaxException;
import java.util.ArrayList;
import io.socket.client.IO;
import io.socket.client.Socket;
import io.socket.emitter.Emitter;
public class MainActivity extends Activity {
public static ArrayList arrayList = new ArrayList();
public ListView listView;
public MyBaseAdapter adapter;
public TextView textView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/*
* Get Socket.io Object
*/
SocketIO socketIo = new SocketIO();
Socket mSocket = socketIo.getSocket(); // get socket
Integer id = socketIo.getId(); // get Website ID
if(mSocket == null) {
socketIo.Connection();
mSocket = socketIo.getSocket();
mSocket.on("message", new Emitter.Listener() {
/*
* Message Listener
*/
@Override
public void call(Object... args) {
Boolean isset = false;
try {
JSONObject object = (JSONObject) args[0];
String _id = object.getString("_id");
String message = object.getString("message");
JSONObject obj = new JSONObject();
obj.put("direction", "fb-lt");
obj.put("message", message);
obj.put("date", "2017-05-29T12:15:49.245Z");
for(int i = 0; i < arrayList.size(); i++){
ListData ld = (ListData) arrayList.get(i);
String id = ld.getId();
if(_id.equals(id)){
JSONArray Data = ld.getData();
Data.put(obj);
ld.setDescription(message);
arrayList.set(i, ld);
isset = true;
Log.d("LOG", message);
}
}
if(!isset) {
JSONArray jsonArray = new JSONArray();
jsonArray.put(obj);
ListData ld = new ListData();
ld.set_id(_id);
ld.setID(1);
ld.setTitle("Klient:");
ld.setDescription(message);
ld.setData(jsonArray);
arrayList.add(ld);
}
} catch (JSONException e) {
e.printStackTrace();
}
changed();
}
});
}
/*
* Populate a listview
*/
listView = (ListView) findViewById(R.id.listView);
adapter = new MyBaseAdapter(this, arrayList);
listView.setAdapter(adapter);
/*
* OnItemClickListener
*/
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(MainActivity.this, Conversation.class);
intent.putExtra("item", position);
startActivity(intent);
TextView textView = (TextView) view.findViewById(R.id.descitem);
textView.setTypeface(null, Typeface.NORMAL);
}
});
textView = (TextView) findViewById(R.id.count);
}
private void changed() {
runOnUiThread(new Runnable() {
@Override
public void run() {
adapter.notifyDataSetChanged();
Log.d("LOG:", "adapter refresh");
}
});
}
}
MyBaseAdapter 类：
package com.example.seadog.fb_dialog;
import android.content.Context;
import android.graphics.Typeface;
import android.util.Log;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import java.util.ArrayList;
public class MyBaseAdapter extends BaseAdapter {
Context context;
ArrayList<ListData> items = new ArrayList();
LayoutInflater inflater;
int id = 0;
public MyBaseAdapter(Context context, ArrayList items) {
this.context = context;
this.items = items;
inflater = LayoutInflater.from(this.context);
}
@Override
public int getCount() {
return items.size();
}
@Override
public ListData getItem(int position) {
return items.get(position);
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
MyViewHolder mViewHolder;
if (convertView == null) {
convertView = inflater.inflate(R.layout.list_item, parent, false);
mViewHolder = new MyViewHolder(convertView);
convertView.setTag(mViewHolder);
} else {
mViewHolder = (MyViewHolder) convertView.getTag();
}
ListData currentListData = getItem(position);
id = position > 0 ? getItem(position - 1).getID() : 0;
mViewHolder.Title.setText(currentListData.getTitle());
mViewHolder.Desc.setText(currentListData.getDescription());
if(1==1){
mViewHolder.Title.setVisibility(View.GONE);
}else {
if (id != currentListData.getID()) {
mViewHolder.Title.setVisibility(View.VISIBLE);
} else {
mViewHolder.Title.setVisibility(View.GONE);
}
}
return convertView;
}
private class MyViewHolder {
TextView Title, Desc;
public MyViewHolder(View item) {
Title = (TextView) item.findViewById(R.id.txtitem);
Desc = (TextView) item.findViewById(R.id.descitem);
Typeface title = Typeface.createFromAsset(context.getAssets(), "fonts/DroidSans.ttf");
Title.setTypeface(title);
Typeface desc = Typeface.createFromAsset(context.getAssets(), "fonts/DroidSans.ttf");
Desc.setTypeface(desc, Typeface.BOLD);
}
}
}
@覆盖 protected void onRestart() {
Intent intentBack = new Intent(getApplicationContext(),MainActivity.class);
startActivity(intentBack);
super.onRestart();
}
您返回此活动后没有任何回电。
您可以重写 onResume() 方法或 startActivityForResult 并在 onAcitvityForResult 方法中执行某些操作。