I'm trying to create an async task to handle a whole bunch of database entries and then let the user know that the entry has been made with a textView that appends to itself. I understand that I cannot touch the views inside the doInBackground, but I cannot get any other methods to work. Can anyone explain to me on how to get my code to work inside of an AsyncTask?
Code:
private class DBADDITION extends AsyncTask<Object, Void, Object> {
#Override
protected String doInBackground(Object... params) {
DBAdapter my_database = new DBAdapter(getApplicationContext());
logout.append("\n" + "Start" + " ");
my_database.open();
String temp = input.getText().toString();
int i = Integer.parseInt(temp);
for (int j = 1; j <= i; j++) {
db.createEntry("example", 10 + j);
logout.setText("\n" + j + logout.getText());
}
db.close();
return "it worked";
}
protected void onProgressUpdate(Integer... progress) {
}
}
You need to override the onPostExecute() method. This is automatically called after the doInBackground() method. Also this is on the UI thread and hence you can modify your textView here.
In case , you need to perform some UI updation before the doInBackground() then you override the onPreExecute() method.
Also, remove instances of any UI element updation from your doInBackground() like setText()
You use Activity.runOnUIThread() to setText, like these:
private class DBADDITION extends AsyncTask<Object, Void, Object> {
#Override
protected String doInBackground(Object... params) {
DBAdapter my_database = new DBAdapter(getApplicationContext());
logout.append("\n" + "Start" + " ");
my_database.open();
final String temp = input.getText().toString();
int i = Integer.parseInt(temp);
for (int j = 1; j <= i; j++) {
db.createEntry("example", 10 + j);
youractivity.this.runOnUiThread(new Runnable() {
public void run() {
logout.setText("\n" + j + logout.getText());
}
);
}
db.close();
return "it worked";
}
protected void onProgressUpdate(Integer... progress) {
}
}
logout.setText()
You can not perform operation on UI from a different Thread. All the UI Operations have to be performend on the UI thread. Since logout is a TextView object, you can not touch it directly from the doInBackground method, since it runs on a different Thread. YOu should use a Handler instance or, you have a reference to your Activity, you should call runOnUiThread. runOnUiThread allows you to post a Runnable on the looper queue of the UI Thread, without the need to instantiate an Handler.
final int finalJ = j;
runOnUiThread(new Runnable() {
public void run() {
logout.setText("\n" + finalJ + logout.getText());
}
});
runOnUiThread(new Runnable() {
public void run() {
logout.append("\n" + "Start" + " ");
}
});
Related
I am trying to get the hang of the SwingWorker class but I am getting an unexpected behaviour I can not solve.
In my background() method, I am publishing an increasing counter which should be logged as the progress into console.
Somehow the chunks.getSize()-1 always print out 0 instead of the incremented counter variable I am providing using publish(counter). What am I doing wrong here?
SwingWorker sw = new SwingWorker<Boolean, Integer>() {
#Override
protected Boolean doInBackground() throws Exception {
int counter = 0;
for (TickerStatistics ticker : tickers) {
candleData.put(ticker.getSymbol(), rc.getCandlestickBars(ticker.getSymbol(), interval));
counter++;
publish(counter);
}
return true;
}
#Override
protected void done() {
System.out.println(candleData);
}
#Override
protected void process(List<Integer> chunks) {
System.out.println(chunks.size() - 1 + " / " + tickers.size());
}
};
I have a ArrayList that I fetch from internet. Now I am performing the list retrieval using Handler postdelayed. Like below in the onCreate of the activity.
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
lis_dat.remove(lis_dat.size() - 1);
if (gri_not_lis) {
rv_3r_ada.notifyItemRemoved(lis_dat.size());
} else {
rv_3r_2c_ada.notifyItemRemoved(lis_dat.size());
}
List<String> lis_of_dat;
int cou = 0, pos = lis_dat.size();
String gen_sta, gen_end, gen_mon;
if (yea) {
String[] mon_sym = new DateFormatSymbols().getMonths();
lis_of_dat = Arrays.asList(mon_sym);
} else {
int how_man;
if (lis_is_new) {
how_man = 500;
} else {
how_man = 15;
}
if (day_in_bet(sta, end) <= how_man) {
gen_sta = sta;
gen_end = end;
} else {
gen_sta = sta;
Calendar cal = Calendar.getInstance();
cal.setTime(db_han.con_dat(sta));
cal.add(Calendar.DATE, how_man);
gen_end = USE_DAT.format(cal.getTime());
}
lis_of_dat = gen_dat_in_bet(gen_sta, gen_end);
}
for (String dat : lis_of_dat) {
if (yea) {
Date date = get_mon_dat(dat, YEA.format(db_han.con_dat(sta)));
gen_sta = get_mon_fir_or_las_dat(date, true);
gen_end = get_mon_fir_or_las_dat(date, false);
gen_mon = dat;
} else {
gen_sta = dat;
gen_end = null;
gen_mon = mon;
}
add_to_lis(gen_sta, gen_end, gen_mon, pos, gri_not_lis);
pos++;
}
pos_f[0] = pos;
cou_f[0] = cou;
is_loa = false;
}
}, 1000);
Now my question is this 1000 milliseconds here may vary in different devices. On whom the UI will stay frozen. So what's the alternative of this. Instead of waiting for 1 sec how can I wait till the UI loading is complete and then I do the retrieval?
I could use AsyncTask but then the task will stay running till the task is complete even if I go to another activity. but i don't need the task running after onPause is called. So how do I do it?
You can use AsyncTask which running in separate thread, your keeps UI responsive . You can cancel it in onPause of Activity by calling **asyncTaskRunner.cancel(true) **
private class AsyncTaskRunner extends AsyncTask<String, String, String> {
private String resp;
ProgressDialog progressDialog;
#Override
protected String doInBackground(String... params) {
return resp;
}
#Override
protected void onPostExecute(String result) {
}
#Override
protected void onPreExecute() {
}
#Override
protected void onProgressUpdate(String... text) {
}
}
You can save instance of handler and then remove all call backs in
onPause of the activity.
private Handler handler = new Handler();
handler.postDelayed(() -> {
// do you task here
},1000);
#Override
public void onPause() {
super.onPause();
handler.removeCallbacksAndMessages(null); // this is important
}
And if you want something which do not freeze UI without any delay,
there you go
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Executors.newSingleThreadExecutor().submit(() -> {
// Do you task here without any delay it will not freeze the UI
});
}
You can also try this,
class MyThread implements Runnable{
#Override
public void run() {
// Your Task Here, put your all calculations Here
}
}
and then in onCrate()
ExecutorService executor = Executors.newSingleThreadExecutor();
executor.submit(new MyThread());
and then in onPause() or onDestory()
executor.shutdownNow();// this will stop the thread instantly
Right now, when I change the activity, my thread seams to go to sleep or something. And when I come back to the main activity, there are two threads running, doing the same things. I'm not sure if this is the case, but it seems like it's something equal.
...
public class MainActivity extends Activity {
public static double cowCount = 195;
public static double income = 0.100;
static boolean twiceCow = false, Threadrunning = false;
...
public void inc() {
new Thread(new income()).start();
}
class income implements Runnable {
#Override
public void run() {
for (int i = 0; i < 20;) {
final int value = i;
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.post(new Runnable() {
#Override
public void run() {
cowCount = cowCount + income;
refresh();
}
});
}
}
}
This is how my thread looks like.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
handler = new Handler();
checkThread();
}
private void checkThread() {
if (Threadrunning == false)
inc();
Threadrunning = true;
}
public void inc() {
new Thread(new income()).start();
}
...
public void refresh () {
TextView myTextView = (TextView)findViewById(R.id.myText);
myTextView.setText("You Have " + String.valueOf((nf.format(cowCount)) + " Cows!"));
}
I don't really understand what I've done wrong.
Please review this post: http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html
Consider your activity re-start as the same thing as a config change.
This pattern, i.e. using a retained Fragment as a container for your thread, and proxying UI updates via callbacks to your activity, is a pattern that will work much better for you.
In your case you'd need only a single TaskCallback for your UI refresh(), e.g. onRefreshCowCount(int cows);
I am having a problem with getting the result from an asyncTask in a separate class. I have followed from a similar questions answer on here but I cant see where I have gone wrong.
My AsyncTask is in a separate class for easy calling, I needed to be able to have the notice that the asyntask had completed and then start the next activity.
I would welcome any help as I am not sure quite where I have gone wrong.
public class StartScreen extends Activity{
ProgressDialog pd;
CountDownTimer waitTimer;
public static final String APP_PREFERENCES = "AppPrefs";
SharedPreferences settings;
SharedPreferences.Editor prefEditor;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start_screen);
settings = getSharedPreferences(APP_PREFERENCES, MODE_PRIVATE);
// getPreferences();
// prefEditor = settings.edit();
waitTimer = new CountDownTimer(2000, 300) {
public void onTick(long millisUntilFinished) {
//called every 300 milliseconds, which could be used to
//send messages or some other action
}
public void onFinish() {
//After 2000 milliseconds (2 sec) finish current
//if you would like to execute something when time finishes
pd = ProgressDialog.show(StartScreen.this,"Title","Detail text",true,false,null);
getPreferences();
}
}.start();
}
private void getPreferences() {
String UserName = settings.getString("UserName", null);
if (UserName != null) {
// the key does not exist
Intent intent=new Intent(StartScreen.this,InitialPreferences.class);
startActivity(intent);
} else{
//if (UserName.equals(UserName)){
// handle the value
dataTask();
//pd.dismiss();
}
}
private void dataTask() {
// TODO Auto-generated method stub
new DATATask(this).execute(new FragmentCallback(){
#Override
public void onTaskDone() {
startMainAct();
}
});
}
private void startMainAct() {
Intent intent=new Intent(StartScreen.this,MainActivity.class);
startActivity(intent);
}
public interface FragmentCallback {
public void onTaskDone();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.start_screen, menu);
return true;
}
}
AsyncTask:
public class DATATask extends AsyncTask<Void, Void, ArrayList<String>> {
private FragmentCallback mFragmentCallback;
public void execute(FragmentCallback fragmentCallback) {
mFragmentCallback = fragmentCallback;
}
ArrayList<String> arr_data=new ArrayList<String>();
private Context context;
public DATATask(Context context)
{
this.context = context;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected ArrayList<String> doInBackground(Void... params) {
Document docVts, docTide;
String shippingList, tideTimes;
try {
docVts = Jsoup.connect("https://vts.mhpa.co.uk/main_movelistb.asp").timeout(600000).get();
Elements tableRows = docVts.select("table.dynlist td:eq(0),td:eq(1),td:eq(3),td:eq(4),td:eq(7),td:eq(8)");
tableRows.size();
for(int i = 1; i < 80; i++){//only allows x results from vts list, from 1 not 0. 0 produces needless results
shippingList = tableRows.get(i).text().replaceAll(" | ", "") +"\n";
arr_data.add(shippingList);// add value to ArrayList
System.out.println(shippingList);
};
docTide = Jsoup.connect("http://www.mhpa.co.uk/search-tide-times/").timeout(600000).get();
Elements tideTimeOdd = docTide.select("div.tide_row.odd div:eq(0)");
Elements tideTimeEven = docTide.select("div.tide_row.even div:eq(0)");
Elements tideHightOdd = docTide.select("div.tide_row.odd div:eq(2)");
Elements tideHightEven = docTide.select("div.tide_row.even div:eq(2)");
Element firstTideTime = tideTimeOdd.first();
Element secondTideTime = tideTimeEven.first();
Element thirdTideTime = tideTimeOdd.get(1);
Element fourthTideTime = tideTimeEven.get(1);
Element firstTideHight = tideHightOdd.first();
Element secondTideHight = tideHightEven.first();
Element thirdTideHight = tideHightOdd.get(1);
Element fourthTideHight = tideHightEven.get(1);
System.out.println("first tide time: " + firstTideTime.text() + " " + firstTideHight.text());
System.out.println("second tide time: " + secondTideTime.text() + " " + secondTideHight.text() );
System.out.println("third tide time: " + thirdTideTime.text() + " " + thirdTideHight.text());
System.out.println("fourth tide time: " + fourthTideTime.text() + " " + fourthTideHight.text());
{
/*
Work with data - all is OK
*/
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return arr_data;//<< return ArrayList from here
}
#Override
protected void onPostExecute(ArrayList<String> result) {
mFragmentCallback.onTaskDone();
}
}
Thanks for any help.
You are not calling the correct AsyncTask.execute(). The correct execute will invoke the onPreExecute() then doInBackground() then onPostExecute().
new DATATask(this).execute(new FragmentCallback(){
#Override
public void onTaskDone() {
startMainAct();
}
});
}
will call this method (the wrong one):
public void execute(FragmentCallback fragmentCallback) {
mFragmentCallback = fragmentCallback;
}
What you want to do is change this method to - setFragmentCallBack(FragmentCallback);
Then in the OnPostExecute() add this: startMainAct();
instead of doing this:
#Override
public void onTaskDone() {
startMainAct();
}
After this is done, then call the new DATATask(this).execute();
which will invoke the preExecute(), doInbackground, and PostExecute()
What you are doing is adding the FragCallback to the DataTask and not invoking the correct execute function.
I hope this helps.
Actually you did not execute your AsyncTask. You should call "super.execute(Params... params);" in you overloaded execute(FragmentCallback) method.
In your Activity:
DataTask dataTask = new DataTask();
dataTask.execute();
In your AsyncTask class:
onPostExecute(){
//put your intent to start the activity or whatever you want to do when it finishes
}
I think it is much simpler than you are making it. Hope that helps. Also, see AsyncTask Android example
You didn't execute the AsyncTask. Calling DATATask.execute(FragmentCallback) will just assign the callback to your task. You need to call either AsyncTask#execute(Runnable), AsyncTask#execute(Params...) or AsyncTask#executeOnExecutor(Executor exec, Params... params).
Also, I would pass the callback to DATATask via the constructor or a setter, instead of creating a new overloaded execute(FragmentCallback) method. It can easily confuse people.
I currently have one class with 4 methods. I need to change that to AsyncTask. Every method receives different parameters (File, int, String ...) to work with and connects to different URL with post or get. My question is can I still somehow have all those operations in one AsyncTask class or I will need to create new AsyncTask class for every method?
private class Task extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
}
This depends if you need all 4 AsyncTasks to run simultaneously or if they can run sequentially.
I would imagine they can run sequentially since that's how they are running currently in the Main thread, so just pass all the needed parameters and execute their operations one by one. In fact, if the functions are already written, just move those functions into your AsyncTask class:
MainActivity.java:
public static final int FILE_TYPE = 0;
public static final int INT_TYPE = 1;
public static final int STRING_TYPE = 2;
taskargs = new Object[] { "mystring", new File("somefile.txt"), new myObject("somearg") };
new Task(STRING_TYPE, taskargs).execute();
AsyncTask
private class Task extends AsyncTask<URL, Integer, Long> {
private Int type;
private Object[] objects;
public Task(Int type, Object[] objects) {
this.type = type;
this.objects = objects;
}
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
}
//obviously you can switch on whatever string/int you'd like
switch (type) {
case 0: taskFile();
break;
case 1: taskInteger();
break;
case 2: taskString();
break;
default: break;
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
protected void taskFile(){ //do something with objects array }
protected void taskInteger(){ //do something with objects array }
protected void taskString(){ //do something with objects array }
}