I've problem with:
public void GetNews() {
if (mClient == null) {
return;
}
new AsyncTask<Void, Void, Void>() {
#Override
protected Void doInBackground(Void... params) {
try {
final List<News> results = newsTable.execute().get();
runOnUiThread(new Runnable() {
#Override
public void run() {
newsAdapter.clear();
for (News news : results) {
newsAdapter.add(news);
}
}
});
} catch (Exception e) {
createAndShowDialog(e, "Chyba");
}
return null;
}
}.execute();
}
App every crashed when executing this code :-(
Code get rows from table in azure mobile services.
Any ideas?
Without seeing your full code sample, my guess is that you've not initialized newsAdapter in a proper way and it is failing when adding there. Share your full code sample and error logs and I can try and be more specific.
Related
I have an asynchronous task in Android Studio, to send and receive data from a server as follows.
private class myTask extends AsyncTask<Void, Void, Integer> {
Exception excepccion;
protected void onPreExecute() {
super.onPreExecute();
Mensaje.mensajeConectandoseSicoy(actMetodoPago,getString(R.string.msg_conexion_sicoy));
}
#Override
protected Integer doInBackground(Void... params) {
try {
return new Servidor().guardarObtnerInfoServidorSicoy(ACCION_PAGAR_PEDIDO);
} catch (Exception e2) {
excepccion = e2;
return -1;
}
}
#Override
protected void onPostExecute(Integer respuesta) {
Mensaje.detenerMensajeConectandoseSicoy();
...
}
Where:
public static void mensajeConectandoseSicoy(Context context, String mensaje){
pd = new ProgressDialog(context);
pd.setMessage(mensaje);
pd.setCancelable(false);
Handler pdCanceller = new Handler();
pd.show();
}
public static void detenerMensajeConectandoseSicoy(){
if (pd.isShowing()){
pd.dismiss();
}
}
This process works very well until a user reported problems and discovered that their internet is of very poor quality.
When the task is running onPostExecute, that is, when the server has already responded, it is again executed onPreExecute, and this triggers a series of errors.
I solved it by putting a Boolean type flag variable, to avoid the problem.
My question is:
Is there a way to do that control in a better way?
In my application, there are multiple asynctasks. Please let me know why doInBackground of an asynctask sometimes does not getting called. Its onPreExecute method gets called. Is there any issue because of multiple asynctasks or something else?
/* ASync class for test table */
public class TestAsynch extends AsyncTask<String, Void, String>{
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
String status = null;
String result1=API_Manager.getInstance().sendTestData(userName);
try {
if(result1 != null) {
// save in db
}
}
}
catch( Exception e) {
e.printStackTrace();
}
return status;
}
#Override
protected void onPostExecute(String status) {
}
}
If your project has multiple asynctasks you must check that there is a limit of asynctasks that can be executed. When you create a new AsyncTask it will be added on a Pool and will be execute only when is possible.
Check this answer:
Multitasking on android
And the docs: ThreadPoolExecutor
Here is an example on how properly handle multiple AsyncTasks AsyncTaskManager
OnPreExecute() gets called on the UI thread and doInBackground() is called on the background thread.
There is one dedicated background thread for the async task. This behaviour can be changed if you want to.
http://android-er.blogspot.in/2014/04/run-multi-asynctask-as-same-time.html
Now, say you have multiple instances of async task and I'm assuming you are calling execute() to run the async tasks. This will trigger all the preExecute immediately since UI thread is free but for the doInBackground it will triggered one by one. Hence it may take some time for the next async task to start.
doInBackground should run on a loop using a Boolean to check before execution. Before your Task is being executed, set a global boolean (may be true/false) depends on which you prefer and values add on thread should call runOnUiThread.
startExect = true;
new TestAsynch().execute();
then change this
public class TestAsynch extends AsyncTask<String, Void, String>{
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
String status = null;
String result1=API_Manager.getInstance().sendTestData(userName);
try {
if(result1 != null) {
// save in db
}
}
}
catch( Exception e) {
e.printStackTrace();
}
return status;
}
#Override
protected void onPostExecute(String status) {
}
}
to this
public class TestAsynch extends AsyncTask<String, Void, String> {
String result1 = null;
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected String doInBackground(String... params) {
String status = null;
result1=API_Manager.getInstance().sendTestData(userName);
while (startExecute) {
Thread exe = new Thread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(5);
}
catch( Exception e) {
e.printStackTrace();
}
runOnUiThread(new Runnable() {
#Override
public void run() {
if(result1 != null) {
// save in db
}
}
});
}
}); exe.start();
}
return status;
}
#Override
protected void onPostExecute(String status) {
}
}
I am trying to check if there is an active internet connection, and after searching, I found a working code answered by Levit:
https://stackoverflow.com/a/27312494/2920212
This seems to work fine except sometimes, it causes a lag where it appears like the app is frozen. I know its because the isOnline function is not run in a background thread. I have searched but unable to implement the background thread properly. Please find below the code:
public boolean isOnline() {
Runtime runtime = Runtime.getRuntime();
try {
Process ipProcess = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
int exitValue = ipProcess.waitFor();
return (exitValue == 0);
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
return false;
}
Here is what I've tried:
private void ChecOnline() {
class CheckURL extends AsyncTask<Void, Void, Boolean> {
#Override
protected Boolean doInBackground(Void... params) {
return isOnline();
}
#Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
String myresult = Boolean.toString(result);
Toast.makeText(getApplicationContext(), myresult, Toast.LENGTH_LONG).show();
}
}
CheckURL ucc = new CheckURL();
ucc.execute();
Nothing happens when ChecOnline(); is called.
Try it using AsyncTask
private class CheckOnlineStatus extends AsyncTask<Void, Integer, Boolean> {
#Override
protected Boolean doInBackground(Void... params) {
//This is a background thread, when it finishes executing will return the result from your function.
Boolean isOnline = isOnline();
return isOnline;
}
protected void onPostExecute(Boolean result) {
//Here you will receive your result from doInBackground
//This is on the UI Thread
}
}
Then you will call
new CheckOnlineStatus().execute();
to execute your code
Hey everyone just getting started with Android testing and I am trying to test an async task. Here is the async task code. I am following this SO post Android AsyncTask testing with Android Test Framework. The runTestOnUiThread is not found in AndroidTestCase however. If I understand this correctly if its not run on the ui thread then the test finishes before the async task completes? Any help is greatly appreciated !
public class BackendTest extends AndroidTestCase {
private static MyApi myApiService = null;
private Context context;
public void testAsyncJoke () throws Throwable{
// create a signal to let us know when our task is done.
final CountDownLatch signal = new CountDownLatch(1);
final AsyncTask<Pair<Context, String>, Void, String> myTask = new AsyncTask<Pair<Context, String>, Void, String>() {
#Override
protected String doInBackground(Pair<Context, String>... params) {
if(myApiService == null) { // Only do this once
MyApi.Builder builder = new MyApi.Builder(AndroidHttp.newCompatibleTransport(), new AndroidJsonFactory(), null)
.setRootUrl("https://androidnanodegreprojectfour.appspot.com/_ah/api/");
myApiService = builder.build();
}
context = params[0].first;
String name = params[0].second;
try {
return myApiService.sayHi(name).execute().getData();
} catch (IOException e) {
return e.getMessage();
}
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
signal.countDown();
}
};
// Execute the async task on the UI thread! THIS IS KEY!
runTestOnUiThread(new Runnable() {
#Override
public void run() {
myTask.execute("Do something");
}
});
signal.await(30, TimeUnit.SECONDS);
// The task is done, and now you can assert some things!
assertTrue("Happiness", true);
}
}
I'm executing the practically identical code (besides the return statement) in onCreate() in two different ways:
once in a Thread (that works)
and once in an AsyncTask
Somehow the Exception thrown in the AsyncTask can't even be debugged... do you have an idea why this code doesn't work in the AsyncTask and why I can't debug de Exception? (It is not present as a variable)
public class TrainingProgressActivity extends ActivityTemplate {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_training_progress);
// the not working AsyncTask variant
new ProgressGetterTask().execute("");
// the working Thread variant
new Thread(new Runnable() {
public void run() {
try {
RestTemplate restTemplate = RestTemplateFactory.createRestTemplate();
FeatureSetCollectionProgress i = restTemplate.postForObject(URLHelper.BASE_PATH+"training/progress", getDevice(), FeatureSetCollectionProgress.class);
System.out.println(i.getMobilityProgress().get(0).getTransportationMeanType().toString());
} catch(Exception e) {
System.out.println("ex");
e.printStackTrace();
}
}}).start();
}
/**
* ProgressGetterTask. (not working ???)
*/
private class ProgressGetterTask extends AsyncTask<String, FeatureSetCollectionProgress, FeatureSetCollectionProgress> {
protected FeatureSetCollectionProgress doInBackground(String... urls) {
try {
RestTemplate restTemplate = RestTemplateFactory.createRestTemplate();
return restTemplate.postForObject(URLHelper.BASE_PATH+"training/progress", getDevice(), FeatureSetCollectionProgress.class);
} catch(Exception e) {
e.printStackTrace();
return null; // setting breakpoint here, 'e' cannot be resolved to a variable.
}
}
protected void onPostExecute(FeatureSetCollectionProgress featureSetCollectionProgress) {
if(featureSetCollectionProgress!=null) {
} else {
}
}
}
}