I have a splash screen activity(ACTIVITY A) which on load completion opens ACTIVITY B
ACTIVITY B ** consists of a button which opens **ACTIVITY C
ACTIVITY A loads a list using async task
I want this loaded list to be displayed in ACTIVITY C when opened
I have read many posts on how to pass values from 1st activity to 3rd activity and tried implementing all those but nothing helped
Evven tried passing the list object via intents from ACTIVITY A > ACTÌVITY B > ACTIVITY C but didnt work
Finally i have used " jacksons library " to convert the loaded list into a jsonstring then put it in sharedpreferences in ACTIVITY A , then retrive the jsonstring from sharedpreferences covert it back to list object in ** ACTIVITY C** and display the list
But the list is not getting displayed
What to do and is there any better process
splash activity(ACTIVITY A)
public class SplashActivity extends Activity{
List<ParseObject> ob;
List<CodeList> codelist = null;
ObjectMapper mapper;
SearchPreferences searchpref;
#Override
public void onCreate(Bundle savedInstanceState){
// TODO: Implement this method
super.onCreate(savedInstanceState);
setContentView(R.layout.splash);
mapper = new ObjectMapper();
searchpref = new SearchPreferences();
new DataTask().execute();
}
public class DataTask extends AsyncTask<Void, Void, List<CodeList>>{
#Override
protected List<CodeList> doInBackground(Void[] p1){
codelist = new ArrayList<CodeList>();
try {
ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("InterActivity");
query.orderByAscending("_created_at");
ob = query.find();
for (ParseObject inter : ob) {
CodeList map = new CodeList();
map.setIntroduction((String) inter.get("intro"));
codelist.add(map);
}
return codelist;
}
catch (ParseException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(List<CodeList> result){
try{
String jsonsearchlist = mapper.writeValueAsString(result);
Intent i = new Intent(SplashActivity.this, MainActivity.class);
searchpref.save(SplashActivity.this, jsonsearchlist);
startActivity(i);
}
catch (JsonProcessingException e){}
}
}
}
ACTIVITY C
public class SearchActivity extends Activity{
protected EditText searchedittext;
ImageButton searchButton;
List<ParseObject> ob;
List<CodeList> splashcodes;
FinalAdapter fnladapter;
SearchPreferences searchpref;
ObjectMapper mapper;
#Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.search_layout);
searchpref = new SearchPreferences();
mapper = new ObjectMapper();
String jsonsearchobj = searchpref.getValue(SearchActivity.this);
try{
splashcodes = (List<CodeList>) mapper.readValue(jsonsearchobj, CodeList.class);
final ListView searchedlist = (ListView) findViewById(R.id.searchlist);
fnladapter = new FinalAdapter(SearchActivity.this, splashcodes);
searchedlist.setAdapter(fnladapter);
}
catch (IOException e){}
}
}
You were on the right path: Loop your information through the 2nd activty. Please note, that CodeList must be serializable.
public class SplashActivity extends Activity{
...
protected void onPostExecute(ArrayList<CodeList> result){
Intent intent = new Intent(SplashActivity.this, SoCalledBActivity.class);
intent.putExtra("YOUR_UNIQUE_KEY",result);
this.startActivity(intent);
}
}
public class SoCalledBActivity extends Activity{
...
Button trigger = (Button) findViewById(R.id.trigger);
trigger.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
//get result list
ArrayList<CodeList> result = (ArrayList<CodeList>) this.getIntent().getExtras().get("YOUR_UNIQUE_KEY");
Intent intent = new Intent(SoCalledBActivity.this, SearchActivity .class);
//add list for C activity
intent.putExtra("YOUR_UNIQUE_KEY",result);
this.startActivity(intent);
}
});
public class SearchActivity extends Activity{
...
public void onCreate(Bundle savedInstanceState){
//extract list
ArrayList<CodeList> result = (ArrayList<CodeList>) this.getIntent().getExtras().get("YOUR_UNIQUE_KEY");
//do whatever you want with your list...
}
...
}
Create a global class and put that list in that class. Once you finish with filling the list, access the list data in Activity C.
Related
I'm developing a feed app, where people can make posts and these posts will populate a RecyclerView.
I have a FAB button that leads to a post activity, but when I post and then comeback to the MainActivity the list is not updated. But when I use the logout button and log back in, the list gets updated, or when I launch the activity it works.
I think this happens because my Async function gets called to work on onCreate, but I can't work like these, I need the AsyncTask to automatically fetch, otherwise people won't get the list updated in real time.
Could you please show me a light in the dark? Here are the codes for MainActivity, PostActivity and logout function from another class.
Main Activity:
public class MainActivity extends AppCompatActivity {
private AppCompatActivity activity = MainActivity.this;
private RecyclerView recyclerViewNews;
private List<Noticia> listNoticias;
private NewsRecyclerAdapter newsRecyclerAdapter;
private DBNoticias databaseHelper;
private Button btnLogout;
private LinearLayoutManager mLayoutManager;
UserSession userSession;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
userSession = new UserSession(getApplicationContext());
recyclerViewNews = findViewById(R.id.recyclerViewNews);
btnLogout = findViewById(R.id.btlogout);
TextView usuario = findViewById(R.id.textView5);
/**
* Olá mundo by Alciomar
*/
SharedPreferences sharedPreferences = getSharedPreferences("Reg", Context.MODE_PRIVATE);
String uName = sharedPreferences.getString("Name", "");
usuario.setText(uName.toUpperCase());
try {
btnLogout.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
userSession.logoutUser();
}
});
} catch (Exception e) {
e.printStackTrace();
}
initStuff();
getDataFromPostgres();
FloatingActionButton fab = findViewById(R.id.fabNews);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, PostNews.class);
startActivity(intent);
}
});
}
/**
* This method is to initialize objects to be used
*/
private void initStuff() {
try {
listNoticias = new ArrayList<>();
newsRecyclerAdapter = new NewsRecyclerAdapter(listNoticias);
mLayoutManager = new LinearLayoutManager(getApplicationContext());
mLayoutManager.setReverseLayout(true);
mLayoutManager.setStackFromEnd(true);
recyclerViewNews.setLayoutManager(mLayoutManager);
recyclerViewNews.setItemAnimator(new DefaultItemAnimator());
recyclerViewNews.setHasFixedSize(true);
recyclerViewNews.setAdapter(newsRecyclerAdapter);
databaseHelper = new DBNoticias(activity);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* This method is to fetch all user records from SQLite
*/
private void getDataFromPostgres() {
// AsyncTask is used that SQLite operation not blocks the UI Thread.
new AsyncTask<Void, Void, Void>() {
#Override
protected Void doInBackground(Void... params) {
listNoticias.clear();
for (DBNoticias dbNoticias : databaseHelper.getNewsList()) {
Noticia noticia = new Noticia();
noticia.setUser_id(dbNoticias.getId());
noticia.setNewsTitle(dbNoticias.getNewsTitle());
noticia.setNewsMessage(dbNoticias.getNewsPost());
listNoticias.add(noticia);
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
newsRecyclerAdapter.notifyDataSetChanged();
}
}.execute();
}
Post News Activity:
public class PostNews extends AppCompatActivity {
private DBNoticias dbNoticias;
private Button btnpostar;
private EditText editTextCDNewsTitle;
private EditText editTextCDNewsPost;
private Noticia noticia;
private SharedPreferences sharedPreferences;
public void alert(String titulo, String txt){
AlertDialog alertDialog = new AlertDialog.Builder(PostNews.this).create();
alertDialog.setTitle(titulo);
alertDialog.setMessage(txt);
alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
alertDialog.show();
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_post_news);
btnpostar = findViewById(R.id.btn_postar);
dbNoticias = new DBNoticias();
editTextCDNewsTitle = findViewById(R.id.EditTextNewsTitle);
editTextCDNewsPost = findViewById(R.id.EditTextNewsPost);
}
public void salvarNoticia(View view) {
try {
{
String newsTitle = editTextCDNewsTitle.getText().toString();
String newsPost = editTextCDNewsPost.getText().toString();
if (!(editTextCDNewsTitle.getText().toString().equals("") || editTextCDNewsTitle.getText() == null ||
editTextCDNewsPost.getText().toString().equals("") || editTextCDNewsPost.getText() == null
)) {
sharedPreferences = getSharedPreferences("Reg", Context.MODE_PRIVATE);
String uName = sharedPreferences.getString("Name", "");
String uEmail = sharedPreferences.getString("Email", "");
int uIdUser = sharedPreferences.getInt("IdUser", 0);
dbNoticias.setNewsTitle(newsTitle);
dbNoticias.setNewsPost(newsPost);
dbNoticias.setIdUser(uIdUser);
dbNoticias.salvar();
noticia = new Noticia();
Toast.makeText(getApplicationContext(), "Notícia postada com sucesso",
Toast.LENGTH_LONG).show();
editTextCDNewsTitle.setText("");
editTextCDNewsPost.setText("");
}
}
}
catch (Exception e){
alert("Erro", e.getMessage());
}
}
Thank you in advance if you read and try to help!
There are multiple ways to do this:
Method 1 – Use onResume()
If you call your getDataFromPostgres() method in onResume instead of onCreate, it'll fetch data and refresh list every time the activity wakes from a pause (for example coming back from another activity)
// existing code
#Override
public void onResume(){
super.onResume();
getDataFromPostgres()
}
(This would be the simplest solution)
Method 2 – Poll the DB continuously
If there are other services that might be updating the database and you need to always show the latest state in the activity, another way (although really inefficient) would be to keep refreshing the list after a defined time period (let's say 10 seconds as an example).
How to run an async task for every x mins in android?
Method 3 – Use onActivityResult
If you want to update the list only when a new entry has been created in the second activity, you can use onActivityResult to notify the first activity on action and then refresh your list there.
How to manage `startActivityForResult` on Android?
Please use this, it's working for me
newsRecyclerAdapter.notifyItemInserted(position);
newsRecyclerAdapter.notifyDataSetChanged();
This is my first time to write Android code and I am stark with a problem.
In the MainActivity, I use AsyncTask to request "Category" list to create buttons. The MainActivity buttons can be clicked and it redirects to GetProductsActivity with an extras String "Category(e.g.drink)". In the GetProductsActivity, I request server again using "Category" to get "Products" list to create product button.
Here is the problem: the code create button first, then AsyncTask request server to get "Products" list, I want to get the "Products" list before creating the button. What should I do?
"orga.getAttributes" is the function to request server.
Here is MainActivity
public class MainActivity extends AppCompatActivity {
private ArrayList<String> data = new ArrayList<String>();
List<String> attributes = new ArrayList<String>();
List<String> categoryList = new ArrayList<String>();
final Organisation orga = Organisation.getInstance();
private class CallSocketTask extends AsyncTask<Integer, Integer, String> {
protected String doInBackground(Integer... nochnix) {
orga.SetInit();
categoryList = orga.getAttributes(orga.GET_CATEGORIES,null,true);
return null;
}
protected void onPostExecute(String string) {
//attributes = orga.getAttributes(orga.GET_PRODUCTS_BY_CATEGORY,null,true);
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new CallSocketTask().execute();//orga.stop();
//requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);
setContentView(R.layout.activity_main);
LinearLayout layer = (LinearLayout) findViewById(R.id.layer);
//getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.activity_main);
for(int i=0; i < categoryList.size(); i++)
{
Button button = new Button(this);
button.setId(i);
final String category = categoryList.get(i);
button.setText(category);
//click action
View.OnClickListener productHandler = new View.OnClickListener(){
public void onClick(View v) {
// doStuff
Intent intentMain = new Intent(MainActivity.this ,
GetProductsActivity.class);
intentMain.putExtra("categroy",category);
MainActivity.this.startActivity(intentMain);
Log.i("Content "," Main layout Click to Get Products by Category");
}
};
button.setOnClickListener(productHandler);
layer.addView(button);
}
}
}
Here is the GetProductsActivity
public class GetProductsActivity extends AppCompatActivity{
private ArrayList<String> data = new ArrayList<String>();
List<String> attributes = new ArrayList<String>();
final Organisation orga = Organisation.getInstance();
String category;
private class CallSocketTask extends AsyncTask<Integer, Integer, String> {
protected String doInBackground(Integer... nochnix) {
Bundle extras = getIntent().getExtras();
if (extras != null) {
category = extras.getString("categroy");
Log.i("Category Selected",category);
}
//orga.SetInit();
attributes = orga.getAttributes(orga.GET_PRODUCTS_BY_CATEGORY,category);
Log.i("Product number ",attributes.size()+"");
//attributes = orga.getAttributes("getProducts","getCategories","Orangensaft");
return null;
}
protected void onPostExecute(String string) {
//Log.i("Result ","");
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//this.notifyAll();
CallSocketTask myTask = new CallSocketTask();
myTask.execute();//orga.stop();
setContentView(R.layout.get_products);
LinearLayout layer = (LinearLayout) findViewById(R.id.productsLayer);
//getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.activity_main);
//Bundle extras = getIntent().getExtras();
//data= extras.getStringArrayList("products");
Log.i("Product number OnCreate",attributes.size()+"");
for(int i=0; i < attributes.size(); i++)
{
Log.i("Product",attributes.get(i));
Button button = new Button(this);
button.setId(i);
button.setText(attributes.get(i));
layer.addView(button);
}
}
}
Move your code for setting up the buttons into onPostExecute.
Solve the problem quite easy: use Thread.sleep() in onCreate() function, so loop button can wait for the AsyncTask running.
Non-static inner AsyncTask may lead to memory leaks, check some gotchas.
Thread.sleep() is a bad way. What if the request "Category" runs longer because of network issues?
Buttons can be created in a method YourActivity.createButtons() which should be called in onPostExecute().
I am programming a messaging app and I want to add users in a group. However, when a list of users pops up and I select one from the list, it doesn't pass the string (the username) to the other activity. All I get is an empty list.
Here is my code:
First Activity = Sending data (usernames from list) through putExtra()
public class ListUsersActivity extends Activity {
private String currentUserId;
private ArrayAdapter<String> namesArrayAdapter;
private ArrayList<String> names;
private ListView usersListView;
private Button logoutButton;
private ProgressDialog progressDialog;
private BroadcastReceiver receiver = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list_users);
Parse.initialize(this, "embpZ0spRUv5XwDgI23innll1sgHg0KZNiKzg6kl", "LPsU4UffPeqFXkQB1GfLCIJ4kvg20llPgbOnLise");
currentUserId = ParseUser.getCurrentUser().getObjectId();
names = new ArrayList<>();
ParseQuery<ParseUser> query = ParseUser.getQuery();
query.whereNotEqualTo("objectId", currentUserId);
query.findInBackground(new FindCallback<ParseUser>() {
public void done(List<ParseUser> userList, com.parse.ParseException e) {
if (e == null) {
for (int i=0; i<userList.size(); i++) {
names.add(userList.get(i).getUsername().toString());
}
usersListView = (ListView)findViewById(R.id.usersListView);
namesArrayAdapter =
new ArrayAdapter<String>(getApplicationContext(),
R.layout.user_list_item, names);
usersListView.setAdapter(namesArrayAdapter);
usersListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> a, View v, int i, long l) {
Intent goBackToAddPoolIntent = new Intent(ListUsersActivity.this, addNewPoolActivity.class);
addNewPoolActivity checker = new addNewPoolActivity();
checker.checkIfUserIsSelected(usersListView.getItemAtPosition(i).toString());
goBackToAddPoolIntent.putExtra("username", usersListView.getItemAtPosition(i).toString());
startActivity(goBackToAddPoolIntent);
}
});
} else {
Toast.makeText(getApplicationContext(),
"Error loading user list",
Toast.LENGTH_LONG).show();
}
}
});
}
Second Activity = Receiving data from putExtra()
public class addNewPoolActivity extends Activity {
private static ArrayList<String> addedUsers;
private ArrayAdapter <String> addedUserAdapter;
private boolean userIsSelected;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_new_pool);
Button addMembers = (Button) findViewById(R.id.bAddMembers);
addedUsers = new ArrayList<>();
//addedUsers.add("Group Members");
addMembers.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent showUsersToSelect = new Intent(addNewPoolActivity.this, ListUsersActivity.class);
startActivity(showUsersToSelect);
}
});
ListView addedUsersList = (ListView) findViewById(R.id.addedUsersListView);
addedUserAdapter = new ArrayAdapter<>(this, R.layout.user_list_item, addedUsers);
addedUsersList.setAdapter(addedUserAdapter);
if(userIsSelected){
Bundle extras = getIntent().getExtras();
addedUsers.add(extras.getString("username"));
}
}
public void checkIfUserIsSelected(String user){
if (user!=null){
userIsSelected = true;
}else{
userIsSelected = false;
}
}
Since the default value for a boolean is false, the code is never called because
if(userIsSelected){
will always evaluate to false since you have declared the varaible as
private boolean userIsSelected;
and the first snippet here is in onCreate() so it will only run the first time the Activity is created.
Maybe you are wanting to call checkIfUserIsSelected(someUser) before that code but without more context of what you hope to accomplish, it's hard to say.
Possibly, you want to use startActivityForResult() in some way?
In addition to #codeMagic 's answer (Since your boolean value is false, it won't call the statement that you are adding the new data). It's also because of you parse the Data "username" after you setAdapter of your ListView. So basically you are setting the data, and then trying to add the new data you parsed to the list. Either you need to do it before setting your data set to your adapter, or call addedUsersAdapter.notifyDataSetChanged() to refresh your listView's data set.
addedUserAdapter = new ArrayAdapter<>(this, R.layout.user_list_item, addedUsers);
addedUsersList.setAdapter(addedUserAdapter);
Bundle extras = getIntent().getExtras();
// Check if the username has been sent to this Activity.
if(extras != null && extras.containsKey("username")){
addedUsers.add(extras.getString("username"));
// Refresh Your Data Set
addedUserAdapter.notifyDataSetChanged();
}
Here is the code:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
overridePendingTransition(R.anim.fadein, R.anim.fadeout);
setContentView(R.layout.startpage);
rowItems = new ArrayList<RowItem>();
//... Filling this array.
}
Later, from another activity StartPage.rowItems.size() throw NullPointerException
It can be 0 (failed to retrieve data or I did .clear()), but how, the hell, it became null? I definitely never set it to null.
One more point - this array variable is public static and I use it from another activity. Can it be possible android unloads parent activity (what contains all global variables for the whole app)?
P.S. I cannot check it more thoroughly, because this error is not appears in my emulator/devices, but I got reported it on Google Play. So I can't check what was before and when the array became null...
Thank you
More exact code:
public class StartPage extends Activity implements View.OnTouchListener {
public static List<RowItem> rowItems;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
overridePendingTransition(R.anim.fadein, R.anim.fadeout);
setContentView(R.layout.startpage);
rowItems = new ArrayList<RowItem>();
pDialog = new ProgressDialog(this);
pDialog.setMessage("Loading data...");
pDialog.setCancelable(false);
pDialog.show();
gc=new GetData();gc.execute();
}
public class GetData extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
rowItems.clear();
inProgress=true;
}
#Override
protected Void doInBackground(Void... arg0) {
ServiceHandler sh = new ServiceHandler();
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
items = jsonObj.getJSONArray(TAG_COINS);
for (int i = 0; i < itemss.length(); i++) {
JSONObject c = items.getJSONObject(i);
String id = c.getString(TAG_ID).toUpperCase();
String price = c.getString(TAG_PRICE);
String name = c.getString(TAG_NAME);
RowItem item = new RowItem(id, name, price);
rowItems.add(item);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
inProgress=false;
pDialog.dismiss();
}
}
Then call another activity:
public boolean onTouch(View view, MotionEvent event) {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_UP:
int x = (int) event.getX();
int y = (int) event.getY();
int w=view.getWidth()-20;
int h=view.getHeight()-20;
if (x<w*0.05 || x>w*0.95 || y<h*0.13 ) return false; // Misclicked
if (x<w*0.5 && y<h*0.38) {
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
}
}
return true;
}
On another activity (MainActivity), try to refresh the listview with the data from main activity:
public class MainActivity extends ListActivity implements View.OnClickListener {
void refresh_list() {
if (StartPage.rowItems.size()>0) { <-- Here is NPE
ListAdapter adapter = new CustomListAdapter(MainActivity.this,R.layout.list_item,StartPage.rowItems);
setListAdapter(adapter);
((BaseAdapter) getListAdapter()).notifyDataSetChanged();
}
}
Google play report:
Caused by: java.lang.NullPointerException
at halfprice.coinmanager.MainActivity.refresh_list(MainActivity.java:116)
at halfprice.coinmanager.MainActivity.onCreate(MainActivity.java:105)
at android.app.Activity.performCreate(Activity.java)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java)
Hope this helps...
you are loading your data in static ArrayList and Acessing it to different activity. its not good practice to do.
Let me first tell your answer as you have created this object in Oncreate(). Its better you make create it Globally than this problem will not occure.
Example :
public class StartPage extends Activity implements View.OnTouchListener {
public static List<RowItem> rowItems = new ArrayList<RowItem>();
OnCreate(){
//and perform the action you want to do.
}
//Hope this will help you definately.
Now Another Method which is the good Practice in Programming language
Passing data object from one Activity to another is simple, If you want to pass Array object than the object should be serialized. Eg;
ArrayList rowItems = new ArrayList();
for Passing array object you have to use intent PutExtra, Eg:
Intent intent = new Intent(SplashScreen.this, MainActivity.class);
intent.putExtra("key",array); startActivity(intent);
//intent.putExtra("key",array); will show error if your Model class is not implements Serializable eg: public class Model implements Serializable{
String id;
String price;
String name;
//generate your getter setter and set data in to this.
}
//For getting data in to another class just use
ArrayList<Model> data = (ArrayList<Model>)getIntent().getSerializable("key");
Now you can play arround with this data object. You should always try to play around with private or protected object.
Hope this will help you.
If i'm not mistaken:
When your activity is launched, the onCreate() method is called.
But when you come back to the same activity from another activity, then the onCreate method is skipped and onResume() method is called..so my suggestion is to initialize in the onResume() method
#Override
protected void onResume(Bundle savedInstanceState) {
overridePendingTransition(R.anim.fadein, R.anim.fadeout);
setContentView(R.layout.startpage);
rowItems = new ArrayList<RowItem>();
//... Filling this array.
}
This answer might not solve your current problem ( not enough code to give a suggestion) but will help you head in the right direction.
Do provide a central data store for your objects, you should consider using singleton design pattern. Also, since the data will be accessed from multiple threads, you should make the arraylist (in your case) thread safe.
Note: if you are using synchronized list, you should lock the object to prevent access when it is iterated.
I have two major classes in my project. The first is for creating the connection between the client and the server. The second is for switching between activities.
first:
public class MyActivity extends Activity{
private ListView mList;
private ArrayList<String> arrayList;
private MyCustomAdapter mAdapter;
public TCPClient mTcpClient;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
boolean flag = getIntent().getBooleanExtra("flag",false);
arrayList = new ArrayList<String>();
final EditText editText = (EditText) findViewById(R.id.editText);
Button send = (Button)findViewById(R.id.send_button);
Button menu = (Button)findViewById(R.id.button1);
if (flag == true)
{
//relate the listView from java to the one created in xml
mList = (ListView)findViewById(R.id.list);
mAdapter = new MyCustomAdapter(this, arrayList);
mList.setAdapter(mAdapter);
new connectTask().execute("");
Intent myIntent = new Intent(MyActivity.this,Menu.class);
startActivity(myIntent);
}
send.setOnClickListener(new View.OnClickListener() {
// #Override
public void onClick(View view) {
String message = editText.getText().toString();
//clean the listView to 1 item
if (message.equals("clean"))
{
arrayList.removeAll(arrayList);
mList.removeAllViewsInLayout();
}
//add the text in the arrayList
arrayList.add("c: " + message);
//sends the message to the server
if (mTcpClient != null) {
mTcpClient.sendMessage(message);
}
//refresh the list
mAdapter.notifyDataSetChanged();
editText.setText("");
}
});
//change Activity to live screen mode (live)
menu.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent myIntent = new Intent(MyActivity.this, Menu.class);
startActivity(myIntent);
}
});
}
public class connectTask extends AsyncTask<String,String,TCPClient> {
#Override
protected TCPClient doInBackground(String... message) {
//we create a TCPClient object and
mTcpClient = new TCPClient(new TCPClient.OnMessageReceived() {
// #Override
//print the message as an Item
public void messageReceived(String message) {
//this method calls the onProgressUpdate
publishProgress(message);
}
});
mTcpClient.run();
return null;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
//in the arrayList we add the messaged received from server
arrayList.add(values[0]);
// notify the adapter that the data set has changed. This means that new message received
// from server was added to the list
mAdapter.notifyDataSetChanged();
}
}
}
the object TCPClient mTcpClient is the major factor in my app. I use it communicate with the server. In addition, even if I switch between activities it is still running properly so I still get info from server even though I am not in that activity.
second:
public class Menu extends Activity
{
public MyActivity myActivity;
public TCPClient mtcp;
protected void onCreate(Bundle savedInstanceState, MyActivity myActivity)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.menu);
ImageView action = (ImageView) findViewById(R.id.imageView1);
action.setOnTouchListener(new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event)
{
// here I would like to use mTcpClient object mentioned in the first class
return false;
}
});
}
Basically what I need is a help on how to create in the second class reference to the object mTcpClient that is described in the first class.
You are doing it wrong. If you want to use TcpClient class regardless of context it should NOT be related to first Activity. What you should do is to use singleton pattern:
class TcpClient {
protected static TcpClient mInstance = null;
public TcpClient() {
// your init code...
}
public static TcpClient getInstance() {
if( mInstance == null ) {
mInstance = new TcpClient();
}
return mInstance;
}
...
}
and then, whenever you want to use TcpClient you just do:
TcpClient client = TcpClient.getInstance();