Develop Reference

How to wait until thread is completed in android

I have this method updatePosts() that needs to run inside of a thread. it looks like this
public void updatePosts(){
new Thread(){
public void run(){
posts.addAll(pholder.fetchPosts());
System.out.println("size of posts is " + posts.size());
// UI elements should be accessed only in
// the primary thread, so we must use the
// handler here.
}
}.start();
}
It is literally updating the List called "posts". I have this in my onCreate. The problem is, since it is running in a separate thread, it does not complete before my ImageAdapter needs to use the "posts" List.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
updatePosts();
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
GridView gridview = (GridView) findViewById(R.id.gridview);
gridview.setAdapter(new ImageAdapter(this, posts));
gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v,
int position, long id) {
Toast.makeText(MainActivity.this, "" + position,
Toast.LENGTH_SHORT).show();
}
});
}
What options do I have to ensure that the updatePosts can finish before the ImageAdapter get created?

You should use an AsyncTask or any other mechanism that lets you offload a task to a background thread with a callback to the UI on completion.
private class BackgroundTask extends AsyncTask<Void, Void, List<Post>> {
#Override
protected List<Post> doInBackground(Void... params) {
// TODO
return posts;
}
#Override
protected void onPostExecute(List<Post> posts) {
// TODO: update UI
}
}
Another option is to use RxJava,
Observable
.fromCallable(new Callable<List<Post>>() {
#Override
public List<Post> call() throws Exception {
// TODO: get posts
return posts;
}
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(posts -> {
// TODO: update UI
}, throwable -> {
// TODO
})

I think you need to use Handler.
private ImageAdapter mAdapter;
private MyHandler mHandler;
private List<YourData> posts;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
GridView gridview = (GridView) findViewById(R.id.gridview);
mAdapter = new ImageAdapter(this, posts)；
gridview.setAdapter(mAdapter);
gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v,
int position, long id) {
Toast.makeText(MainActivity.this, "" + position,
Toast.LENGTH_SHORT).show();
}
});
mHandler = new MyHandler(this);
updatePosts();
}
public void updatePosts(){
new Thread(){
public void run(){
posts.addAll(pholder.fetchPosts());
System.out.println("size of posts is " + posts.size());
if (mHandler != null) {
mHandler.sendMessage(mHandler.obtainMessage(1));
}
// UI elements should be accessed only in
// the primary thread, so we must use the
// handler here.
}
}.start();
}
private static class MyHandler extend Handler{
private WeakReference<Your Activity name> outer;
public MyHandler(Your Activity name activity){
outer = new WeakReference<>(activity);
}
#Override
public void handleMessage(Message msg){
switch(msg.what){
case 1:
if(outer.get()!=null){
outer.get().mAdapter.refresh(outer.get().posts);
}
break;
default:break;
}
}
}
And in your ImageAdapter,you need add a method:
public void refresh(List<YourData> dataSet){
this.dataSet = dataSet;
notifyDataSetChanged();
}

Combine Activity with Fragment

Learning what I can from the internet and youtube, I'm sure I am not handling this in the appropriate way. I have an existing app which includes a slide out navigation drawer using fragments. I am now trying to get an activity to run within that fragment without any luck. It works when ran on it's own, but after trying to combine the two, I am not able to get "draftactivity" to run properly. The fragment operates as it should.
public class tapsfragment extends Fragment {
public static tapsfragment newInstance() {
tapsfragment fragment = new tapsfragment();
return fragment;
}
public tapsfragment(){}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
((MainActivity) activity).onSectionAttached(2);
}
public class DraftActivity extends Activity {
TextView draftfeed;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.draft_activity);
draftfeed = (TextView) findViewById(R.id.draftfeed);
new PostAsync().execute();
}
class PostAsync extends AsyncTask<Void, Void, Void> {
ProgressDialog pd;
XMLHelper helper;
#Override
protected void onPreExecute() {
pd = ProgressDialog.show(DraftActivity.this, "Taps", "Loading posts for ******.com ...", true, false);
}
#Override
protected Void doInBackground(Void... arg0) {
helper = new XMLHelper();
helper.get();
return null;
}
#Override
protected void onPostExecute(Void result) {
StringBuilder builder = new StringBuilder();
for (ItemValue post : helper.posts) {
builder.append("\nPost: " + post.getTitle());
builder.append("\n");
}
draftfeed.setText(builder.toString());
pd.dismiss();
}
}

Activity can't run in a fragment, it's the other way around.

Tabs with Fragment life cycle

in my app i have a Tabs with fragment classes. i trying to refresh listView in "fragment a" with the new data i insert.
In "fragment b" i have EditText and Button ,that inserting text to the database.
in "fragment a" i have the ListView with the dataBase rows. when "fragment a" is "OnCreateView" i just put the dataBase on a "ArrayList" and past it to my baseAdapter.
but "onCreateView" not refreshing my new data every time i get into the "fragment a" else i goes to "fragment c" and "onDestroy" call on "fragment a".
so my result it was to call : "setUserVisibleHint" override method, and check if it is visible and refreshing the list.
but i dont think it is the good practice .
what should i do?
Class a
public class ListFragment extends Fragment{
basAdapterCustom adapter;
ListView lv;
ArrayList<Clock> list;
private DbHandler hand;
Context context;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.list_fragment, container, false);
context = getActivity();
Log.d(TAG, "onCreateView");
hand = new DbHandler(context);
list = new ArrayList<Clock>();
lv = (ListView) v.findViewById(R.id.listOfShifts);
adapter = new basAdapterCustom(list, getActivity());
lv.setAdapter(adapter);
refreshList();
return v;
}
//like on "resume":
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
// Make sure that we are currently visible
if (this.isVisible()) {
refreshList();
if (!isVisibleToUser) {
// TODO stop
}
}
}
private void refreshList() {
list = hand.getByWorkName();
adapter = new basAdapterCustom(list,getActivity());
lv.setAdapter(adapter);
}
class b:
public class ClockFragment extends Fragment{
DbHandler hand;
Context context;
#Override
public View onCreateView(LayoutInflater inflater,
#Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.clock, container,false);
context = getActivity();
hand = new DbHandler(context);
return v;
}
// ADD to .Db
public void addToDb(View v){
hand.add(new Clock(0, dateDay));
}
}
class mainActivity:
public class MainActivity extends FragmentActivity implements ActionBar.TabListener, OnPageChangeListener{
public static final String TAG = "myClock";
String[] tabMenu = {"FRAG A","FRAG B","FRAG C"};
private ViewPager viewPager;
private TabPagerAdapter mAdapter;
private ActionBar actionBar;
#SuppressLint("NewApi")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(MainActivity.TAG, "OnCreate = MainActivity (Pager");
viewPager = (ViewPager) findViewById(R.id.pager );
actionBar = getActionBar();
mAdapter = new TabPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
for (String tabsNames : tabMenu) {
actionBar.addTab(actionBar.newTab().setText(tabsNames).setTabListener(this));
}
viewPager.setOnPageChangeListener(this);
}
// public void transDialog(){
// Dialog mDialog = new Dialog(this, android.R.style.Theme_Translucent_NoTitleBar_Fullscreen);
// }
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
}
PagetAdapter.class
public class TabPagerAdapter extends FragmentPagerAdapter {
private static final String TAG = "myClock";
public TabPagerAdapter(FragmentManager fm) {
super(fm);
// TODO Auto-generated constructor stub
}
#Override
public Fragment getItem(int index) {
Log.d(TAG, " CLASS : TabPagerAdapter");
switch (index) {
case 0:
return new ListFragment();
case 1:
return new ClockFragment();
case 2:
return new SettingFragment();
default:
break;
}
Log.d(TAG, " CLASS : TabPagerAdapter = "+index);
return null;
}
#Override
public int getCount() {
return 3;
}
}
Please help me i hope you are understand my problem...

You want to update listView in fragment A, after insert data in fragment b? Then  you have a few solutions to choose:
1. Implement communications between fragments via activity. Then B insert date, it send message to activity, that data need to be updated. Then fragment A started, it's ask activity to need update data. For details on implementing this communication check link.
2. Use some bus library, EventBus for example. Then fragment B insert data, it post 'data changed' event to bus. Fragment A checks on start if this event occurs.
3. Use Loaders which "monitor the source of their data and deliver new results when the content changes."

Passing data from activity to swipeable view fragment

Ok, I'm new to android programming and here is my problem. I've got an async task that collects json data from a server on a httpget request and updates a listview fragment in a swipeable view. I want a way to send data(a bunch of strings) from the main TabActivity class to the Tab1Fragment class.
I've done my level best at stripping down the code to the essentials.
NOTE: I've tried the bundle method that I've read in other similar questions, but they all end up throwing NULL pointer exceptions in the fragment, meaning the bundle isn't getting sent.(?)
This is my main Tab Activity:
TabActivity.java
public class TabActivity extends ActionBarActivity implements ActionBar.TabListener {
private String phoneno;
private static String url = "http://my/url/forjson";
//JSON Node Names
private static final String TAG_OPERATOR = "operator";
private static final String TAG_REGNO = "Reg No";
public String operator;
public String regNo;
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Details", "Others"};
Bundle bundle = new Bundle();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tab);
Intent intent = getIntent();
phoneno = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
new JSONParse().execute();
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getSupportActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
/**
* on swiping the viewpager make respective tab selected
* */
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
// on changing the page
// make respected tab selected
actionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// on tab selected
// show respected fragment view
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
/*Private Class to parse JSON*/
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
#Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(TabActivity.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
#SuppressWarnings("finally")
#Override
protected JSONObject doInBackground(String... args) {
//*
JSONParser jParser = new JSONParser();
// Getting JSON from URL
StringBuilder finalUrl = new StringBuilder();
JSONObject jsonForData = new JSONObject();
try{
finalUrl.append(url);
jsonForData = jParser.getJSONFromUrl(finalUrl.toString());
}catch (JSONException e) {
e.printStackTrace();
}
return jsonForData;
}
#Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
Bundle bundle=new Bundle();
bundle.putString("oper", json.getString(TAG_OPERATOR));
bundle.putString("regNo", json.getString(TAG_REGNO));
mAdapter.getData(bundle);
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
In the above code, please understand that the JSONPasrser class that I've instantiated returns a JSONObject from the url and it works. So, no issues there.
Further, my fragment class is a listview as follows:
Tab1Fragment.java
public class Tab1Fragment extends ListFragment{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_tab1, container, false);
String abc = "No Details Presently Available";
//Fill all string values with something
String[] values = new String[2];
for(int i=0;i<values.length;i++)
values[i] = " ";
//Make Sure number of elements match
try{
values[0] = "Provider: " + getArguments().getString("oper");//Gives a NULL value
values[1] = "No: " + + getArguments().getString("regNo");//Gives a NULL value
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this.getActivity(), android.R.layout.simple_list_item_1,values);
// Assign adapter to ListView
setListAdapter(adapter);
}
catch(Exception e){
e.printStackTrace();
Log.w("Error","The App didn't have enough elements specified to populate the listview");
}
return rootView;
}
}
The "abc" string that I've hardcoded should ideally have details sent from the TabActivity class.
I want the above fragment to recieve data from the TabActivity class to populate the listview. Any help is appreciated :)
EDIT: I've changed the adapter class as follows based on Illegal Argument's suggestion.
So now, the bundle is passed as TabActivity->TabsPagerAdapter->Tab1Fragment
But still, NULL value returned.
My Adapter class is now as follows:
TabsPagerAdapter.java
public class TabsPagerAdapter extends FragmentStatePagerAdapter {
Bundle bundle = new Bundle();
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
Fragment fragment = new Tab1Fragment();
this.bundle.putString("operator", "hi");
fragment.setArguments(this.bundle);
return fragment;
case 1:
return new Tab2Fragment();
}
return null;
}
#Override
public int getCount() {
// get item count - equal to number of tabs
return 2;
}
public void getData(Bundle bundle){
this.bundle = bundle;
}
}

I can see that you have successfully passed data via a bundle. Please remove this. from your code below:
this.bundle.putString("operator", "hi");
fragment.setArguments(this.bundle);
change it because it is not required to be accessed that way:
bundle.putString("operator", "hi");
fragment.setArguments(bundle);
On your Tab1Fragment.java you can try something like this:
if(getArguments()!=null){
String sentString = getArguments().getString("operator");
}

How to reload fragment or refresh fragment on TabReselected Using ActionBar Tabs

DESCRIPTION::
There is a ActionBarTab(3-tab) setup, We are linking three fragments
for each Action-Tab, Each fragment contains a listview
Whenever we are clicking Tab, we are sorting data.
In onTabReselect i am calling sort function using interface method,
without error it executes but its not refreshing the listview
MainActivity.java
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Toast.makeText(this, DosUtils.ExecuteDOSCommand(), Toast.LENGTH_SHORT);
// Initialize
FindMyBuffetApplicationCls.initFindMyBuffetApplicationCls(MainActivity.this);
setContentView(R.layout.main_activity);
appContext = getApplicationContext();
//ActionBar
ActionBar actionbar = getActionBar();
actionbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.Tab RatingTab = actionbar.newTab().setText(FindMyBuffetConstants.TAB_NAME_RATING);
ActionBar.Tab PriceTab = actionbar.newTab().setText(FindMyBuffetConstants.SORT_BY_PRICE);
ActionBar.Tab DistanceTab = actionbar.newTab().setText(FindMyBuffetConstants.SORT_BY_DISTANCE);
Fragment SortRestFragmentByRating = new SortRestaurantRating();
Fragment SortRestFragmentByPrice = new SortRestaurantByPrice();
Fragment SortRestFragmentByDistance = new SortRestaurantByDistance();
RatingTab.setTabListener(new MyTabsListener(SortRestFragmentByRating));
PriceTab.setTabListener(new MyTabsListener(SortRestFragmentByPrice));
DistanceTab.setTabListener(new MyTabsListener(SortRestFragmentByDistance));
actionbar.addTab(RatingTab);
actionbar.addTab(PriceTab);
actionbar.addTab(DistanceTab);
FindMyBuffetApplicationCls.comm = (Communicator) new SortRestaurantByPrice();
}
class MyTabsListener implements ActionBar.TabListener {
public Fragment fragment;
public MyTabsListener(Fragment fragment) {
this.fragment = fragment;
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
if(tab.getText().toString()==FindMyBuffetConstants.TAB_NAME_RATING){
if(FindMyBuffetApplicationCls.isRatingOrderByDesc==false){
FindMyBuffetApplicationCls.isRatingOrderByDesc=true;
}
else {
FindMyBuffetApplicationCls.isRatingOrderByDesc=false;
}
}
if(tab.getText().toString()==FindMyBuffetConstants.SORT_BY_PRICE){
if(FindMyBuffetApplicationCls.isPriceOrderByDesc==false){
FindMyBuffetApplicationCls.isPriceOrderByDesc=true;
}
else {
FindMyBuffetApplicationCls.isPriceOrderByDesc=false;
}
FindMyBuffetApplicationCls.comm.RefreshFragment();
}
if(tab.getText().toString()==FindMyBuffetConstants.SORT_BY_DISTANCE){
if(FindMyBuffetApplicationCls.isDistanceOrderByDesc==false){
FindMyBuffetApplicationCls.isDistanceOrderByDesc=true;
}
else {
FindMyBuffetApplicationCls.isDistanceOrderByDesc=false;
}
}
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.replace(R.id.main_container, fragment);
if(tab.getText().toString()==FindMyBuffetConstants.TAB_NAME_RATING){
if(FindMyBuffetApplicationCls.isRatingOrderByDesc==false)
FindMyBuffetApplicationCls.isRatingOrderByDesc=true;
else
FindMyBuffetApplicationCls.isRatingOrderByDesc=false;
}
if(tab.getText().toString()==FindMyBuffetConstants.SORT_BY_PRICE){
if(FindMyBuffetApplicationCls.isPriceOrderByDesc==false)
FindMyBuffetApplicationCls.isPriceOrderByDesc=true;
else
FindMyBuffetApplicationCls.isPriceOrderByDesc=false;
}
if(tab.getText().toString()==FindMyBuffetConstants.SORT_BY_DISTANCE){
if(FindMyBuffetApplicationCls.isDistanceOrderByDesc==false)
FindMyBuffetApplicationCls.isDistanceOrderByDesc=true;
else
FindMyBuffetApplicationCls.isDistanceOrderByDesc=false;
}
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
ft.remove(fragment);
Log.i("TEST TAB",tab.getText().toString());
}
}
SortRestaurantByPrice.java
public class SortRestaurantByPrice extends Fragment implements Communicator{
// Declaration
ListView xmlFragmentListView;
SortRestaurantListViewAdapter listViewAdapter;
View layout;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
layout = inflater.inflate(R.layout.sort_restaurant_by_price, container,false);
xmlFragmentListView = ((ListView) layout.findViewById(R.id.sortrestaurantbypricelistview));
return layout;
}
#Override
public void onDestroyView() {
super.onDestroyView();
//layout = null; // now cleaning up!
}
private void SortRestaurantList(String strSortBy)
throws Exception, TransformerConfigurationException,
TransformerException, FindMyBuffetException {
// Process the Main Screen Data
List<RestaurantDetails> lstRest = null;
lstRest = SAXXMLParser.parse(xmlInputStream);
SortRestaurantListViewAdapter listViewAdapter = new SortRestaurantListViewAdapter(lstRest);
xmlFragmentListView.setAdapter(listViewAdapter);
}
#Override
public void RefreshFragment() {
// TODO Auto-generated method stub
Log.i("hELLO", "refresh requested. Try to reload data for this fragment...");
SortRestaurantList("Price");
}
}
Communicator.java
public interface Communicator {
public void RefreshFragment();
}

Please call notifyDataChanged method on your list in the sortRestaurantList method.
private void SortRestaurantList(String strSortBy)
throws Exception, TransformerConfigurationException,
TransformerException, FindMyBuffetException {
// Process the Main Screen Data
List<RestaurantDetails> lstRest = null;
lstRest = SAXXMLParser.parse(xmlInputStream);
SortRestaurantListViewAdapter listViewAdapter = new SortRestaurantListViewAdapter(lstRest);
xmlFragmentListView.setAdapter(listViewAdapter);
listViewAdapter.notifyDataSetChanged(); // call this on Adapter
}
Infact move the adapter code in the onCreateView method. Only modify (sort) your List lstRest in the SortRestaurant method and after that call the notifyDataSetChanged method.