I am having problems trying to get to onPostExecute to fire on this piece of code, I am new to java and especially multithreading so if what i'm doing is completely wrong please feel free to correct me...need to learn.
So the problem is with this:
public class DataTask extends AsyncTask<Void, Void, Integer> {
Context context;
DataTask(Context context) {
this.context = context.getApplicationContext();
}
// Global Int for counting how many Tasks have been completed
int asynCount = 0;
ArrayList<String> arr_dataVts=new ArrayList<String>();
ArrayList<String> arr_dataNtm=new ArrayList<String>();
ArrayList<String> arr_dataOdas=new ArrayList<String>();
ArrayList<String> arr_dataMetAll=new ArrayList<String>();
ArrayList<String> arr_dataMet3HrTask=new ArrayList<String>();
ArrayList<String> arr_dataTideTask=new ArrayList<String>();
#Override
protected Integer doInBackground(Void... params) {
//VtsAsyncTask
VtsTask task1 = new VtsTask();
task1.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//NtmAsyncTask
NtmTask task2 = new NtmTask();
task2.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//OdasAsyncTask
OdasTask task3 = new OdasTask();
task3.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//MetAllTask
MetAllTask task4 = new MetAllTask();
task4.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//Met3HrTask
Met3HrTask task5 = new Met3HrTask();
task5.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//TideTask
TideTask task6 = new TideTask();
task6.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
return 1;
}
All the tasks execute as should do
but here in the onPostExecute:
#Override
protected void onPostExecute(Integer result) {
if (asynCount == 6){
//start intents for main activity
System.out.println("asynCount has reached= " + asynCount + " so now starting MainActivity");
Intent intent = new Intent(context, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.putStringArrayListExtra("data1", arr_dataVts);
intent.putStringArrayListExtra("data2", arr_dataNtm);
intent.putStringArrayListExtra("data3", arr_dataOdas);
intent.putStringArrayListExtra("data4", arr_dataMetAll);
intent.putStringArrayListExtra("data5", arr_dataMet3HrTask);
intent.putStringArrayListExtra("data6", arr_dataTideTask);
// context.startActivity(intent);
}else{
//update dialogue
}
}
}
The onPostExecute never gets called? I don't know why.
I have tried using Integers, Void and Booleans to get it to return but doesn't work.
All advice is appreciated.
EDIT: I now realise that I should really be using Bundle here for all the extras.
Your DataTask class is unnecessary. The only thing that you are doing in the background is starting several other AsyncTask's you don't need to wrap all of those execute() commands inside of the own AsyncTask because they already get executed in a background thread just by the very nature of AsyncTask.
Each of these other Tasks that you have needs to have it's own onPostExecute() that handles the results from that specific task and does something with it.
EDIT:
Here is some pseudocode of how it might look if you combined all of your operations into a single AsyncTask:
public class DataTask extends AsyncTask<Void, Void, Integer> {
Context context;
DataTask(Context context) {
this.context = context; // <-- you already have a context, you don't need to call getApplicationContext();
}
#Override
protected Integer doInBackground(Void... params) {
doSomeWork();
doSomeOtherWork();
doYetSomeMoreWork();
//...
}
#Override
protected void onPostExecute(Integer result) {
doSomethingWithThe(result);
}
}
The doSomeWork() etc... methods should not be AsyncTasks, just normal methods so that they execute sequentially. That way, when all of them are complete onPostExecute() will be called.
Related
What I have :
I have a SearchActivity which receives an ArrayList (NameDesSearch) from a fragment(after a button click) and it updates a simple listview. When I click a list view item a new view is appearing by the corresponding object (orgDesObj) of the clicked list item. This functionality works well.
Currently receiving list (NameDesSearch) consists of names and descriptions. All are strings.
But, I wanted to show lists names only. Hence I tried creating a function (titlefunc()).
Here a new ArrayList ( NameDesTitles ) was crated to add relevent names only.
Issue:
But, seems like Do In background function is not working by the time I call titlefunc().
Attempts:
I put several Log to capture the point.
I'm using the same function (getLocDesOb()) in the list view on item clicked as well.
Surprisingly it works, even the doInBackground function also works.
But when the search activity creates and titlefunc() is called, search list (finalODescriptionArrayList) in doInBackground is empty().
Form the Logs I receive the content of finalODescriptionArrayList as [] and size as 0.
But, when I click list view item finalODescriptionArrayList updates.
I even tried by moving NameDesSearch = getIntent().getStringArrayListExtra("searched"); outside of the function as well.
Seems like my doInBackground method is calling only when the list item clicked but not activity on creates. Every other function works well. I'm not sure by the time when why my titlefunc() is called, why finalODescriptionArrayList does not update.
I would appreciate any suggestions on this. Thank you !
My Code: I have removed Logs for clearness.
public class SearchActivity extends AppCompatActivity {
ListView searchedListView;
String SearchedWord;
private ArrayAdapter<String> orgAdapter;
ArrayList<String> NameDesSearch = new ArrayList<String>();
ArrayList<String> NameDesTitles = new ArrayList<String>();
private OService OService;
ArrayList<ODescription> finalODescriptionArrayList = new ArrayList<ODescription>();
#RequiresApi(api = Build.VERSION_CODES.N)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
searchedListView = (ListView) findViewById(R.id.searched_list_view);
new GetCourse().execute();
titlefunc();
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, NameDesTitles);
searchedListView.setAdapter(arrayAdapter);
searchedListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String selectedItemText = parent.getItemAtPosition(position).toString();
ODescription orgDesObj = getLocDesOb(selectedItemText);
if (orgDesObj != null) {
Intent intent = new Intent(SearchActivity.this, View.class);
intent.putExtra("sOb", orgDesObj);
startActivity(intent);
}
}
});
}
#SuppressLint("StaticFieldLeak")
private class GetCourse extends AsyncTask<Void, Void, Void> {
#TargetApi(Build.VERSION_CODES.N)
#Override
protected Void doInBackground(Void... voids) {
try {
finalODescriptionArrayList = JsontoObject.jsonToObjectData(getResources().openRawResource(R.raw.newdb));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
public ODescription getLocDesOb(String selectedItemText) {
if (finalODescriptionArrayList == null) {
return null;
}
for (ODescription locDescObj : finalODescriptionArrayList) {
if (locDescObj.getName().equals(selectedItemText) || locDescObj.getDescription().equals(selectedItemText)) {
return locDescObj;
}
}
return null;
}
public void titlefunc() {
NameDesSearch = getIntent().getStringArrayListExtra("searched");
for (String searchNameDes : NameDesSearch) {
ODescription orgDesObj2 = getLocDesOb(searchNameDes);
if (orgDesObj2 != null) {
NameDesTitles.add(orgDesObj2.getName());
}
}
}
}
Attempts After Answer Below
AsyncTask update with onPostExecute. Then Since it take a little bit of time a progress bar added with onPreExecute. titlefunc() in oncreate method removed.
This method works now. But, sometimes the same issue exists. Arraylist to adapter is empty so that listview is empty. Seems like still taking lot of time to do the background task.
Updated AsyncTask
#SuppressLint("StaticFieldLeak")
private class GetCourse extends AsyncTask<Void, Void, Void> {
ProgressDialog progressDialog;
#Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog = new ProgressDialog(SearchActivity.this);
progressDialog.setMessage("Searching");
progressDialog.setCancelable(false);
progressDialog.show();
}
#TargetApi(Build.VERSION_CODES.N)
#Override
protected Void doInBackground(Void... voids) {
try {
finalODescriptionArrayList = JsontoObject.jsonToObjectData(getResources().openRawResource(R.raw.newdb));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
titlefunc();
arrayAdapter.notifyDataSetChanged();
if (progressDialog.isShowing())
progressDialog.dismiss();
}
}
Modifed titlefunc() - to remove duplicates
Set<String > set = new HashSet<>( NameDesTitles);
NameDesTitles.clear();
NameDesTitles.addAll(set);
Your AsyncTask runs asynchronously, in the background. It will (most likely) not be finished when you call titleFunc() (which is what you are seeing).
You can fix this in many ways. One way would be to update the content of your adapter after the AsyncTask completes. You can do this in onPostExecute() of your AsyncTask which will be called when the background processing completes. In that method you can run your titleFunc() or something similar to filter the results you want to display. You then need to tell your Adapter to update the view by calling notifyDatasetChanged() on the Adapter.
I have the following code. My problem is, that I can't get the JSON.execute() to stop/cancel. I spend quite some time looking up possible answers but I wasn't able to find anything that really worked (e.g. JSON.cancel(true)). As soon as I turn the trackerswitch on, the AsnycTask starts running every 3 seconds just like it's supposed to. Is there a way to easily stop the AsyncTask from executing as soon as the trackerswitch is turned off?
private boolean tracking = false;
private Switch trackerswitch;
private final Timer timer= new Timer();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.table_layout);
final Handler handler=new Handler();
final int delay = 4000;
trackerswitch=findViewById(R.id.trackerswitch);
trackerswitch.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
NetworkAccess JSON = new NetworkAccess();
if(trackerswitch.isChecked()){
trackerswitch.setText("Tracking...");
tracking=true;
handler.postDelayed(new Runnable() {
#Override
public void run() {
NetworkAccess JSON = new NetworkAccess();
JSON.execute();
handler.postDelayed(this, delay);
}
},delay);
}
else{
tracking=false;
trackerswitch.setText("Start Tracking");
}
}
});
}
}
This is what's called in the network class:
public class NetworkAccess extends AsyncTask<Void, Void, Void> {
public ArrayList<String> alldata = new ArrayList<>();
public ArrayList<String> locationlist = new ArrayList<>();
int stride;
String data;
#Override
protected Void doInBackground(Void... voids) {//4B4ADC
SOME CODE WHICH ISN'T IMPORTANT FOR MY PROBLEM
alldata.addAll(elementlist);
locationlist.addAll(loctrack);
}
}
catch(IOException | JSONException e){
MainActivity.field1.setText(e.getClass().getCanonicalName());
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
MainActivity.field1.setText(String.format("%20s %20s", alldata.get(0), alldata.get(1)));
COUPLE MORE OF THESE SETTEXT COMMANDS TO FILL A TABLE WITH DATA
}
}
Thanks for your help!
handler.postDelayed() adds objects of the Runnable you provide to the message queue, to be run at the specified interval. You need to remove all the queued objects from the message queue in order to cancel the execution. Calling JSON.cancel(true) does not affect other objects that are already added to the queue.
You'll have to retain a reference to your Runnable implementation and then call handler.removeCallbacks(r) to prevent further executions. Instead of using an anonymous class in handler.postDelayed().
This documentation page sheds more light on the matter.
Also refer this page for what happens when you call cancel(true) on an AsyncTask.
I'm trying to make a simple app that's looks for WiFi networks, and connects to them. I'm currently having a problem with updating the UI.
A few pointers would be great. Thank you for your time.
class UiUpdater extends AsyncTask<Void, Void, List<ScanResult>> {
#Override
protected void onPreExecute() {
super.onPreExecute();
TextView searching = (TextView) findViewById(R.id.searching);
searching.setText("Currently searching...");
}
#Override
protected List<ScanResult> doInBackground(Void... params) {
WifiManager manager = (WifiManager) Client.this.getSystemService(Context.WIFI_SERVICE);
if (!manager.isWifiEnabled())
manager.setWifiEnabled(true);
return manager.getScanResults();
}
#Override
protected void onPostExecute(List<ScanResult> items) {
super.onPostExecute(items);
ArrayList<Items> wifi = new ArrayList<>();
for (ScanResult s : items)
wifi.add(new Items(s.SSID, s.capabilities));
///TextView searching = (TextView) findViewById(R.id.searching);
///searching.setText("");
ListView list = (ListView) findViewById(R.id.list);
Explorer adapter = new Explorer(Client.this, R.layout.listview_item_row, wifi);
list.setAdapter(adapter);
clickListener(list, wifi);
}
}
please use Toast message or logcat or breakpoint to check onPost execute is being called or not
I managed to get it working, but by taking a different approach.
I used the BroadcastReceiver and registerReceiver to get the onReceive event to update the list.
Here's the code:
mWifiManager = (WifiManager)getSystemService(Context.WIFI_SERVICE);
if(!mWifiManager.isWifiEnabled())
mWifiManager.setWifiEnabled(true);
mWifiManager.startScan();
wifiReceiver = new BroadcastReceiver(){
#Override
public void onReceive(Context c, Intent intent)
{
if(mWifiManager != null) {
List<ScanResult> networks = mWifiManager.getScanResults();
showWifi(networks);
}
}
};
registerReceiver(wifiReceiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
Although I haven't managed to understand how AsyncTask works, I did get some nice results with loading a simple progress bar.
I think the problem I encountered was as such:
I started an AsyncTask on another thread.
In the doInBackground, getScanResults started another background thread, leading doInBackground to think the job's done.
onPostExecute was called because doInBackground finished its job.
Bottom line, it wasn't the AsyncTask's fault, it was mine for not knowing that getScanResults starts another background thread.
I have an app connected to a Java Servlet backend by means of an AsyncPost task. The task returns a String to the client representing a json object serialized with Gson.
It works almost fine, the problem is that I'm unable to access the Servlet response message from the class instantiating the call to the ServletPostAsyncTask: ListViewPrenota.class.
The project is structured as follows:
Both within the Servlet and the Client I created the two classes, Tour.class and Tours.class to store my data:
Tour class:
public class Tour {
// some simple int/string/list fields
}
Tours class:
public class Tours {
private List<Tour> tours;
// ...
}
On Client side, in a ServletPostAsyncTask.class, I receive the aforementioned Gson object within doInBackGround(). Within onPostExecute() I deserialize it, this way:
class ServletPostAsyncTask extends AsyncTask<Pair<Context, String>, Void, String> {
private Context context;
Tours tours;
#Override
protected String doInBackground(Pair<Context, String>... params) {
//connect to Servlet and get the serialized Gson object
}
#Override
protected void onPostExecute(String jsonResponse) {
tours = (new Gson().fromJson(jsonResponse, Tours.class));
}
}
Now, from ListViewPrenota.class in Client I am calling the ServletPostAsyncTask:
ServletPostAsyncTask s = new ServletPostAsyncTask();
s.execute(new Pair<Context, String>(ListViewPrenota.this, "tours"));
Tours ttours = s.tours;
Tour tour = ttours.getTours().get(0);
Problem: I receive a java.lang.NullPointerException pointing to Tour tour = ttours.getTours().get(0);
What is the reasong preventing me to access the newly received Tours object from other classes than ServletPostAsyncTask?
Thank you very much
the problem is you are thinking that code runs serially, if you want to use stuff returned from the AsycTask you need to use it in onPostExecute or have a callback that sends the data after it is done
doInBackground(){
//do heavy work
}
onPostExecute(Data data){
//handle data
//send data via interface to activity or class that needs the data
//or just put everything that needs the data in here
}
Ok, it works. Here's what I was able to come up with:
Callback interface:
interface CallBack {
void callBackMethod(Tours tours);//do job
}
Caller class:
class ServletPostAsyncTask extends AsyncTask<Pair<Context, String>, Tours, String>{
private Context context;
Tours tours;
public ListViewPrenota listViewPrenota;
public ServletPostAsyncTask(ListViewPrenota listView){
this.listViewPrenota = listView;
}
#Override
protected String doInBackground(Pair<Context, String>... params) {
//communicate with Servlet and get a HttpResponse
}
#Override
protected void onPostExecute(String jsonResponse) {
tours = (new Gson().fromJson(jsonResponse, Tours.class));
//the callback starts a thread updating the UI in ListViewPrenota
listViewPrenota.callBackMethod(tours);
Toast.makeText(
context,
"Connected. \nTours size: "+ tours.getTours().size(),
Toast.LENGTH_LONG).show();
}
}
The callback interface's implementation within ListViewPrenota:
public class ListViewPrenota extends FragmentActivity implements CallBack{
private ProgressDialog m_ProgressDialog = null;
private Runnable viewOrders;
private TourAdapter m_adapter;
ListView listView;
private ArrayList<Tour> m_tours =null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list_view_prenota);
listView = (ListView) findViewById(R.id.list);
m_tours = new ArrayList<Tour>();
m_adapter = new TourAdapter(this, R.layout.list_row, m_tours);
listView.setAdapter(m_adapter);
getActionBar().setDisplayHomeAsUpEnabled(true); //pulsante drawer
getActionBar().setHomeButtonEnabled(true); //pulsante dietro
ServletPostAsyncTask spat = new ServletPostAsyncTask(ListViewPrenota.this);
String status = spat.getStatus().toString();
spat.execute(new Pair<Context, String>(ListViewPrenota.this,"tours"));
}
public void callBackMethod(final Tours tours){
System.out.println("I've been called back");
viewOrders = new Runnable(){
#Override
public void run() {
getOrders(tours);
}
};
Thread thread = new Thread(null, viewOrders, "MagentoBackground");
thread.start();
m_ProgressDialog = ProgressDialog.show(
ListViewPrenota.this,
"Please wait...",
"Retrieving data ...",
true);
}
public void getOrders(Tours tours){
try{
m_tours = new ArrayList<>();
m_tours.addAll(tours.getTours());
Thread.sleep(2000);
Log.i("ARRAY", "" + m_tours.size());
} catch (Exception e) {
Log.e("BACKGROUND_PROC", e.getMessage());
}
//add tours to the adapter
runOnUiThread(returnRes);
}
private Runnable returnRes = new Runnable() {
#Override
public void run() {
if(m_tours != null && m_tours.size() > 0){
m_adapter.notifyDataSetChanged();
for(int i=0;i<m_tours.size();i++)
m_adapter.add(m_tours.get(i));
}
m_ProgressDialog.dismiss();
m_adapter.notifyDataSetChanged();
}
};
If there's a better way to do it I accept further suggestions.
In the mean time, thank you very much
My problem is this;
I have a AsyncTask that works fine, and on doInBackground() it calls a new class that sync my data to a web service using REST service, i don't have everything on a unique class because i need the same content sync for different activitys and it's easier this way.
What i need is, on the sync procedure, i can get the number of "contacts" and everytime it downloads a contact, removes 1 from the "contacts" lenght, so, i nedd to show on the progress dialog the length of contact and refresh everytime it downloads a new "contact"
hre's my code for the AsyncTask:
public class syncContentTask extends AsyncTask<String, String, Boolean> {
private ProgressDialog mprogress;
private Context context;
//token for JSON header to authenticate
String authToken;
public syncContentTask(Context cxt, String token) {
this.context = cxt;
mprogress = new ProgressDialog(context);
authToken = token;
}
protected void onPreExecute() {
mprogress = ProgressDialog.show(context, "Sync", "Sync in progress...");
}
#Override
protected Boolean doInBackground(String... params) {
syncData syncData = new syncData();
syncData.syncData(context, authToken);
publishProgress(progress);
return true;
}
protected void onProgressUpdate(String... progress) {
//mprogress.setProgress(Integer.parseInt(progress[0]));
}
protected void onPostExecute(Boolean result) {
if (result) {
mprogress.dismiss();
}
}
}
In the Sync Data class i have functions that handles the HttpRequest and database stuff...
can anyone help??
You need to create a listener for your data progress and have it update the progress bar. Right now it looks like this line:
syncData.syncData(context, authToken);
blocks and no updates are provided to your progress indicator until it is done. So, you need something like:
MyListener listener = new MyListener(context);
SyncData syncData = new syncData(listener);
And in your listener have callback methods like myListener.downloadStarted() , myListener.updateProgressBar(int progress) and myListener.downloadCompleted() that your syncData class calls as the download progresses.
For example:
public abstract class SDScanAdapter implements SDScanListener {
public void startScan() {
}
public void updateScanProgress(int scanItemsTotal, int scanItemsCompleted) {
}
public void scanComplete() {
}
}
Then create a listener class:
public class ScanListener extends SDScanAdapter {
#Override
public void scanComplete(String contactName, String action) {
runOnUiThread(scanComplete);
}
#Override
public void startScan() {
runOnUiThread(startScan);
}
#Override
public void updateScanProgress(int scanItemsTotal,
int scanItemsCompleted) {
if (scanCountTotal != scanItemsTotal) {
scanCountTotal = scanItemsTotal;
progressBar.setMax(scanCountTotal);
}
if (scanCountUpdate != scanItemsCompleted) {
scanCountUpdate = scanItemsCompleted;
runOnUiThread(updateScanProgress);
}
}
}
And then for this example you need Runnables (startScan, scanComplete and updateScanProgress) that perform UI tasks, like updating the progress bar. In your case, you may also want to load some of the results, etc.
Then in your AsyncTask you do:
ScanListener listener = new ScanListener();
SyncData syncData = new syncData(listener);
Assuming the SDScanListener class and AsyncTask are all in your Activity. Also, your SyncData calss will need to have a SDScanListener variable that is set when it instantiates. Then, while it does its job, calls are made to the listener methods like:
scanListener.startScan();
And while it progresses, it calls the other methods (and corresponding parameters are passed in).