Develop Reference

ProgressDialog not displaying

I have a progress dialog, I want it to show and dismiss when my method has finished executing. now, I have this:
progressDialog = new ProgressDialog(this);
progressDialog.setMessage("Downloading...");
progressDialog.show();
new Thread(new Runnable() {
#Override
public void run() {
try{
DownloadMethod(s);
progressDialog.dismiss();
}catch (Exception e){
Toast.makeText(prefs.this, "We can't reach the data...Try again", Toast.LENGTH_SHORT).show();
}
}
}).start();
My method DownloadMethod is executed but never shows the dialog.

Actually, It must be throwing an exception with progressDialog.dismiss(); call because you cannot update UI from a worker thread, instead use AsyncTask
e.g pass parameter to constructor
private class DownloadFilesTask extends AsyncTask<Void, Void, Void> {
TypeOf_S s;
public DownloadFilesTask(TypeOf_S s){
this.s = s;
}
#Override
protected Void doInBackground(Void... obj) {
DownloadMethod(s);
return null;
}
#Override
protected void onPostExecute(Void result) {
progressDialog.dismiss();
}
}
and call it like new DownloadFilesTask(s).execute();
or with generic parameter
private class DownloadFilesTask extends AsyncTask<TypeOf_S, Void, Void> {
#Override
protected Void doInBackground(TypeOf_S... obj) {
DownloadMethod(obj[0]);
return null;
}
#Override
protected void onPostExecute(Void result) {
progressDialog.dismiss();
}
}
and call it like new DownloadFilesTask().execute(s);

progressDialog.dismiss();is throwing an exception so move your code inside runOnUiThread() method like this:
runOnUiThread(new Runnable() {
#Override
public void run() {
progressDialog.dismiss();
}
});

as suggested by Pavneet you can use async task as follows where AsyncTask<String, void, String> corresponds to the input type progress value and last is result value you are interested so give data types accordingly.
private class DownloadFilesTask extends AsyncTask<String, void, String> {
protected String doInBackground(String... urls) {
//here do the actual downloading instead of calling the DownloadMethod(s)
}
protected void onPreExecute() {
//here show the dialog
progressDialog.show();
}
protected void onPostExecute(String result) {
//here hide the dialog
progressDialog.dismiss();
}
}
and where you are calling the download function you just call this
progressDialog = new ProgressDialog(this);
progressDialog.setMessage("Downloading...");
new DownloadFilesTask().execute(s);
//here s is assumed to be string type you can give anything

Long delay before AsyncTask doInBackground() starts

I have an Android app where when I switch from Activity A back to Main Activity, then to B, then press button the code calls an AsyncTask.
OnPreExecute() is called right away but it takes about a minute before doInBackground() is called.
I use execute() to start the task. Using executeOnExecutor() has no effect.
Why is there a delay?
I have checked and do not have any other AsyncTasks running.
I am running API 19 KitKat. No choice since it must run on TC-70 using EMDK.
Any ideas on where to start looking?
public class BarcodeHandler
implements EMDKListener, DataListener, StatusListener, ScannerConnectionListener {
#Override
public void onData(ScanDataCollection scanDataCollection) {
String dataString = "test";
new AsyncDataUpdate().execute(dataString);
}
...
}
private class AsyncDataUpdate extends AsyncTask<String, Void, String>
{
#Override
protected void onPreExecute()
{
Log.d("delayTest", "DataUpdate PreExecute()");
}
#Override
protected String doInBackground(String... params) {
Log.d("delayTest", "DataUpdate doInBackground");
return params[0];
}
protected void onPostExecute(String result) {
Log.d("delayTest", "DataUpdate onPostExecute");
if (result != null) {
if (dataListener != null)
dataListener.barCodeListener(result);
}
}
}

IllegalStateException:The content of the adapter has changed but ListView did not receive a notification

Intuitivly, I know, when it throws the IllegalStateException. But in my case, I can't, though, probably guess, where is trouble in the source. I dare say, trouble lines are there:
private class LoadMoreDataTask extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
if (isCancelled()) {
return null;
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
}
OFFSET = OFFSET + COUNT;
getWallsData();
return null;
}
#Override
protected void onPostExecute(Void result) {
mPostListAdapter.notifyDataSetChanged();
wallPostsList.onLoadMoreComplete();
super.onPostExecute(result);
}
#Override
protected void onCancelled() {
wallPostsList.onLoadMoreComplete();
}
there's a logcat message:
java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131099757, class com.costum.android.widget.LoadMoreListView) with Adapter(class android.widget.HeaderViewListAdapter)]

The problem is fixed:the answer was found there !
what I did? I have added, the switcher, Boolean LOADMORE SWITCHER=false; as global visibility and replaced mPostListAdapter.notifyDataSetChanged(); from doInBackground() to getWallsData().
private Boolean LOADMORE SWITCHER=false;
....
private class LoadMoreDataTask extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
if (isCancelled()) {
return null;
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
}
OFFSET = OFFSET + COUNT;
LOADMORE=true;
getWallsData();
return null;
}
#Override
protected void onPostExecute(Void result) {
// mPostListAdapter.notifyDataSetChanged(); was replaced to getWallsData() body
wallPostsList.onLoadMoreComplete();
super.onPostExecute(result);
}
#Override
protected void onCancelled() {
wallPostsList.onLoadMoreComplete();
}
}
.....
getWallsData(){
...
if(LOADMORE){
mPostListAdapter.notifyDataSetChanged();
LOADMORE=false;
}
}
I'm very-very glad to say: I haven't this problem anymore:
java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131099757, class com.costum.android.widget.LoadMoreListView) with Adapter(class android.widget.HeaderViewListAdapter)]

Executing two asynctask in in two different classes

I have 2 AsyncTasks in two different classes but the problem is when the first is do in backgroung state the second is not executed. The first asyncTask if preformed in loop because it needs to update every 5 seconds the new data. If i stop the task (condition = flase) the second one works perfectly.
First class:
public class MapScreen extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map_screen);
UpdateUserCords updateUC = new UpdateUserCords();
updateUC.execute();
}
class UpdateUserCords extends AsyncTask<String, Void, String>
{
#Override
protected String doInBackground(String... params) {
while(condition)
{
//some code in loop...
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
}
}
}
Second class:
public class Groups extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_groups);
getGroups getGr = new getGroups();
getGr.execute(); //not executing, no error or crash
}
class getGroups extends AsyncTask<String, Void, String>
{
ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();
#Override
protected String doInBackground(String... params) {
//some code...
return null;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
}
}
}

After Android API 11, AsyncTasks started to run on serial executor by default, that means that only one task is running at a time. To get the behavior of prior to API 11, which is running on ThreadPoolExecutor, you'll need to specify it in the code like this:
if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.HONEYCOMB) {
myTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
}
else {
myTask.execute();
}
Please take a look here for more information:
http://commonsware.com/blog/2012/04/20/asynctask-threading-regression-confirmed.html
Good luck!
P.S. It's not recommended to use AsyncTask for an infinite thread, AsyncTask purpose is to do a Task on the background, not to run forever, so if you want an infinite thread, I think you should create it as a Thread and not as an AsyncTask.

You asynctasks are in two different activities.
Only one activity is active at any time.

Both classes extend Activity and only one of them is running at the same time.
If you want a task to be execute longer than the lifetime of an activity, you have to wrap it into an Service

How to set adapter of spinner by using Async Task Class

In my code I load a spinner adapter by using Async Task
In My case The ProgressDialog is Not dismissing
This is My code.
I want to show the item after adapter load and the progressDialog is to dismiss
Please Help me, Thanks
private class LoadMoreVehicals extends AsyncTask<Object, Integer, Object> {
#Override
protected void onPreExecute() {
progressBar = ProgressDialog.show(RegistrationScreen.this, "",
"Loading...");
progressBar.setIndeterminate(true);
progressBar.setIndeterminateDrawable(getResources().getDrawable(
R.anim.progressbar_handler));
super.onPreExecute();
}
#Override
protected Object doInBackground(Object... params) {
String countryUrl = ConstantURL.COUNTRY_URL;
getCounty(countryUrl);
countrySpinner
.setAdapter(new MyCustomSpinnerAdapter(
RegistrationScreen.this,
R.layout.spinner_dropdown,
countyList));
return null;
}
#Override
protected void onProgressUpdate(Integer... values) {
progressBar.getProgress();
}
#Override
protected void onPostExecute(Object result) {
progressBar.dismiss();
Log.e("Im in onPostExecute", "");
super.onPostExecute(result);
}
}

While programming in Android you should remember one thing that any task which draws something on the screen should be executed on the main thread. When you set the adapter then android calls the getView() method of the adapter and draws views on the screen. So you should set the adapter in the postExecute() method instead in doInBackground() method.
Here is a small sample to clear my point:
class MyTask extends AsyncTask<Void, Void, Void> {
ProgressDialog pd = new ProgressDialog(MainActivity.this);
#Override
protected void onPreExecute ( )
{
//starting the progress dialogue
pd.show();
}
#Override
protected Void doInBackground (Void... params)
{
//fetch data here
...
...
return null;
}
#Override
protected void onPostExecute (Void result)
{
//set adapter here
...
...
//dismissing the progress dialogue
pd.dismiss();
}
}

In my experience i have so many problems with async runs and UI so now always separate the stuff trying to place the "responsibilities" in each place. So i do something like this:
Create my Async class with the process i want to do and nothing that transform the UI in it
Create a function in UI thread that modify the UI when async task finish, something like OnAsyncTaskComplete(Object response)
Keep communicated the threads
public class MyActivity extends Activity {
private static MyAsyncClass backgroundTask;
private static ProgressDialog pleaseWaitDialog;
//......activity stuff.......
#Override
public void onPause()
{
super.onPause();
//Get rid of progress dialog in the event of a screen rotation or other state change. Prevents a crash.
if (pleaseWaitDialog != null)
pleaseWaitDialog.dismiss();
}
//Function to avoid lose the async thread if the app interrupts (phone rotation, incoming call, etc) RECOMENDED TO HANDLE THIS!!
//Sets the current state after app resume
#Override
public void onResume()
{
super.onResume();
//If there is a background task set it to the new activity
if ((backgroundTask != null) && (backgroundTask.getStatus() == Status.RUNNING))
{
if (pleaseWaitDialog != null)
pleaseWaitDialog.show();
backgroundTask.setActivity(this);
}
}
}
//Logic business after the web service complete here
//Do the thing that modify the UI in a function like this
private void onTaskCompleted(Object _response)
{
//For example _response can be a new adapter
MyList.setAdapter((BaseAdapter)_response);
//or can be a list to create the new adapter
MyList.setAdapter(new MyAdapter(this, (ArrayList<String>)_response));
//or can be anything you want, just try to make here the things that you need to change the UI
}
/**
* Class that handle the async task
*/
public class MyAsyncClass extends AsyncTask<Void, Void, Object>
{
//Maintain attached activity for states change propose
private MyActivity activity;
//Keep the response of the async task
private Object _response;
//Flag that keep async task completed status
private boolean completed;
//Constructor
private MyAsyncClass(MyActivity activity) {
this.activity = activity;
}
//Pre execution actions
#Override
protected void onPreExecute() {
//Start the splash screen dialog
if (pleaseWaitDialog == null)
pleaseWaitDialog= ProgressDialog.show(activity.this,
"PLEASE WAIT",
"Getting results...",
false);
}
//Execution of the async task
protected Object doInBackground(Object...params)
{
//return the thing you want or do want you want
return new ArrayList();
}
//Post execution actions
#Override
protected void onPostExecute(Object response)
{
//Set task completed and notify the activity
completed = true;
_response = response;
notifyActivityTaskCompleted();
//Close the splash screen
if (pleaseWaitDialog != null)
{
pleaseWaitDialog.dismiss();
pleaseWaitDialog = null;
}
}
//Notify activity of async task completion
private void notifyActivityTaskCompleted()
{
if ( null != activity ) {
activity.onTaskCompleted(_response);
}
}
//for maintain attached the async task to the activity in phone states changes
//Sets the current activity to the async task
public void setActivity(MyActivity activity)
{
this.activity = activity;
if ( completed ) {
notifyActivityTaskCompleted();
}
}
}
}
Hope its help you

First of all you cannot set the adapter in the doInBackground
follow this design:
private class LoadMoreVehicals extends AsyncTask<Object, Integer, Object>
{
private ArrayList<Country> countries;
#Override
protected void onPreExecute() {
progressBar = ProgressDialog.show(RegistrationScreen.this, "","Loading...");
progressBar.setIndeterminate(true);
progressBar.setIndeterminateDrawable(getResources().getDrawable(R.anim.progressbar_handler));
super.onPreExecute();
}
#Override
protected Object doInBackground(Object... params) {
String countryUrl = ConstantURL.COUNTRY_URL;
countries = getCounty(countryUrl);
return null;
}
#Override
protected void onProgressUpdate(Integer... values) {
progressBar.getProgress();
}
#Override
protected void onPostExecute(Object result) {
countrySpinner.setAdapter(new MyCustomSpinnerAdapter(RegistrationScreen.this,R.layout.spinner_dropdown,countries));
progressBar.dismiss();
Log.e("Im in onPostExecute", "");
super.onPostExecute(result);
}
}