I know that there are already some discussions and I searched on the internet a lot for a solution, I have 3 get calls (volley) I want to execute one after another because the next get does need variables which were set on the get before this but it doesn't seem to work here. When I debug the whole process it worked fine of course but when running the app normally it doesn't get any data which I would have gotten when debugging it.
Now I tried to set static boolean variables to make this whole thing work but theres so far no success..
public class AsyncToken extends AsyncTask<String , Void, Void> {
private PacketBuilder pb = new PacketBuilder();
private Context context;
AsyncUser u = new AsyncUser(context);
#Override
protected Void doInBackground(String... params) {
while( task1finished == false )
{
try
{
Log.d("App", "Waiting for GetTask");
Thread.sleep(1000);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
Log.d("App", "GetTask finished");
// Do what ever you like
// ...
pb.Get("token", "", params[0], context);
return null;
}
protected void onPostExecute(String ... params)
{
task2finished = true;
}
public AsyncToken(Context context)
{
this.context = context;
}
}
EDIT, the code:
When async task is completed onPostExecute() is called, so start another async task with computed values there. You can have global variables what should be computed or you can pass them through parameters.
//start first async task
new TaskOne().execute();
class TaskOne extends AsyncTask<Void,Void,String>{
String tmp;
#Override
protected String doInBackground(Void... records) {
tmp = computeNeededValue();
return tmp;
}
#Override
protected void onPostExecute(String result) {
new TaskTwo().execute(tmp);
}
)
class TaskTwo extends AsyncTask<String,Void,Void>{
#Override
protected Void doInBackground(String... records) {
//use computed value from first task here
}
#Override
protected void onPostExecute(Void result) {
//start another async task
}
)
Related
I have several activities and one asyncTask that uses the same interface for callback methods as below
The interface used by all
public interface AsyncTaskCallback {
void onCookie(CookieManager cookieManager);
void onResponse(String response);
void onProgress(String... values);
void onError(Exception e);
}
AsyncTask1 is called from all activities as follows
public void exec_taskt() {
alertDialog.SetText("Sending Request...");
AsyncTask1 task1 = new AsyncTask1("https://stackoverflow.com");
task1.setCookieManager(cookiejar);
task1.setCallback(this);
task1.execute();
}
Each Activity also implements the interface
#Override
public void onCookie(CookieManager cookieManager) {
cookiejar = cookieManager;
}
#Override
public void onResponse(String response) {
try {
PostProc(response);
}catch (Exception e){ // ERROR HERE
e.printStackTrace();
}
}
#Override
public void onProgress(String... values) {
alertDialog.SetText(values[0]);
}
#Override
public void onError(Exception e) {
///SAME ERROR HERE TOO
//Toast.makeText(getContext(), e.getMessage(), Toast.LENGTH_LONG).show();
swipeRefreshLayout.setRefreshing(false);
}
private void PostProc(String response) {
//the response string is parsed and displayed in a recyclerview in this method
//this method is slightly different for each activity
}
AsyncTask1
public class AsyncTask1 extends AsyncTask<String, String, String> {
private String address = "";
private CookieManager mCookieManager;
private Exception mException;
private AsyncTaskCallback mCallback;
public AsyncTask1 (String page) {
this.address = page;
}
public void setCookieManager(CookieManager cm) {
this.mCookieManager = cm;
}
public void setCallback(AsyncTaskCallback cb) {
this.mCallback = (AsyncTaskCallback) cb;
}
#Override
protected String doInBackground(String... strings) {
try{
//all code here is executed without error
//code skipped for simplicity
// basically just loads the given url and then...
publishProgress("Page Loaded");
mCallback.onCookie(mCookieManager);
mCallback.onResponse(response);
return response;
} catch (Exception e) {
publishProgress("Error");
e.printStackTrace();
mCallback.onError(e);
return "";
}
#Override
protected void onProgressUpdate(String... values) {
Log.d(tag, TextUtils.join(",", values));
mCallback.onProgress(values);
super.onProgressUpdate(values);
}
}
The errors I get are marked
ERROR HERE
in the code above. and the message is as follows
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
My main suspect is the PostProc() method in the activity that does play with the UI component. But doesnt implementing the interface in the activity mean that part of the code runs in the main UI thread? I know you can pass the activity instance to the asyncTask and call the PostProc() method from postexecute of the asyncTask but I would like to explore an alternative way to it, since the same asynctask is accessed by other activities as well. the returns are the same for all activities. Only the PostProc Method is different.
Thanks in advance
Instead of using callback interface you can use a android.os.Handler() which is associated with the Looper.getMainLooper() to update the views like:-
AsyncTask1 task1 = new AsyncTask1(android.os.Handler(Looper.getMainLooper(), msg -> {
// handle message sent from asyncTask
return false;
}), url);
Then in task1 send the message using using the handler
public AsyncTask1 (Handler handler, String page) {
this.address = page;
this.handler = handler;
}
then ,
Message message = new Message();
message.obj = uiData;
handler.sendMessage(message);
The handler onHandleMessage will always execute on the main looper !
I'm trying to do a setText() on a Textview (already instantiate in the onCreate()) called by a Handler and using the ruiOnUiTread() but I have a nullPointerException on the Textview.
Where can the problem come from?
I saw in the debug that the instance of the activity was not the same between the instantiation and the setText() while I do not change activity but impossible to instantiate it in the same place as the setText().
private TextView ambianceTextView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ambianceTextView = findViewById(R.id.valeur_ambiance);
StarterKillerPidroid.getInstance().startApp();
}
private final Runnable retrieveData = new Runnable() {
public void run() {
try {
setText();
} catch (Exception e) {
e.printStackTrace();
}
handlerRecup.postDelayed(retrieveData, 1000);
}
};
public void setText(){
runOnUiThread(new Runnable() {
#Override
public void run() {
ambianceTextView.setText("test");
}
});
}
public void doAfterLogin() {
handlerRecup.postDelayed(retrieveData, 10000);
}
the runnable is started by a function called by a callback of an http request with Volley
public class StarterKillerPidroid {
void startApp() {
//Sending a request
PostmanPidroid.getInstance().login();
}
public void ackLogin(Boolean isValid) {
if (isValid) {
ActivityMain.getInstance().doAfterLogin();
} else {
PostmanPidroid.getInstance().login();
}
}
}
The class Postman :
public class Postman {
public void login(){
// Parameters
String email = "test#tes";
String password = "test";
// Encoding the request with parameters
JsonObjectRequest request = EncoderDecoderPidroid.getInstance()
.encodeRequestLogin(email, password);
// Sending the request
sendRequest(request);
}
void sendRequest(StringRequest message){
// Creating the queu if it's not create
if (queue == null) {
queue = Volley.newRequestQueue(context);
}
// Adding the request to the queue
queue.add(message);
}
}
When a success response is received, this callback is called :
private Response.Listener<JSONObject> callbackLogin =
new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response) {
...
StarterKillerPidroid.getInstance().ackLogin(true);
}
};
Basically, this kind of problem is due to the instance. It may be possible that your textview instance is not initialized. One more thing using handler directly for updating UI thread is not a good idea. Instead of directly updating Ui with handler you should use FunctionalInterface for doing this.
FunctionalInterface is a good approach for such cases.
A functional interface is an interface that contains only one abstract method. They can have only one functionality to exhibit. From Java 8 onwards, lambda expressions can be used to represent the instance of a functional interface. ... Runnable, ActionListener, Comparable are some of the examples of functional interfaces.
Java has a predefined FunctionalInterface Callable. It goes something like this
public static void doDid(final Callable<Void> callable) {
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
try {
callable.call();
handler.postDelayed(this, every * repeattime);
} catch (Exception e) {
e.printStackTrace();
}
}
}, every * tempvalue);
}
and use this for updating UI in this way
doDid(new Callable<Void>() {
#Override
public Void call() {
textView.setText("Your text");
return null;
}
});
There is one open-source library available for Android which works like a charm is such cases called Predictor. You can download it from here and import in your project. You can also contribute in this project for saving many developers life.
Do you wanna see how predictor can do this?
Predictor.every(3).second().doDid(new Job<Void>() {
#Override
public Void run() {
textView.setText("Your text");
return null;
}
});
What can you do with predictor?
Predictor gives you several ways of handling multithreading some of them are as follows:
Predictor.every(3).second().doDid(something());
Predictor.every(5).minutes().doDid(something());
Predictor.every().hour().doDid(something());
Predictor.every().week().doDid(something());
Predictor.every().month().doDid(something());
and many more...
Try this way:
private final Runnable retrieveData = new Runnable() {
public void run() {
try {
ambianceTextView = (TextView) findViewById(R.id.valeur_ambiance);
setText();
} catch (Exception e) {
e.printStackTrace();
}
handlerRecup.postDelayed(retrieveData, 1000);
}
};
I'm actually trying to build a WebSocket client application on Android with the nv-websocket-client.
But I'm stuck with interfaces in my doInBackground function.
I'm trying to use a AsyncTask for the WebSocket connetion, but I'm stuck when I have to pass to onPostExecute the message from onTextMessage :/
private class Reseau extends AsyncTask<Void, Void, String> {
// This is run in a background thread
#Override
protected String doInBackground(Void... params) {
socket.addListener(new WebSocketAdapter() {
#Override
public void onTextMessage(WebSocket websocket, String message) throws Exception {
// Here I want to return the String message to onPostExecute
// How to do it ? return message do not work because onTextMessage is void
}
});
try { socket = new WebSocketFactory()
.setConnectionTimeout(5000)
.createSocket(adresse[0] + adresse[1])
.connect();
}
catch (IOException e) { e.printStackTrace(); } catch (WebSocketException e) { e.printStackTrace(); }
return "I want to pass message from onTextMessage to onPostExecute";
}
// This runs in UI when background thread finishes
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
zone.append(result);
}
}
I can use a RunOnUIThread or enable StrictMode but this is not the good method to do that job.
Thank you for your help !
I need help with checking if the phone my app is running on is connected to the Internet. I started with pinging an IP to check connection. It looked like this:
protected Boolean checkInternetConnection(Void... params) {
try {
InetAddress ipAddr = InetAddress.getByName("https://www.google.com");
if (!ipAddr.isReachable(10000)) {
return false;
} else {
return true;
}
} catch (Exception e) {
Log.e("exception", e.toString());
return false;
}
}
}
However, it allways threw the NetworkOnMainThreadException, so I used AsyncTask:
private class CheckConnectionTask extends AsyncTask<Void, Void, Boolean> {
#Override
protected Boolean doInBackground(Void... params) {
try {
InetAddress ipAddr = InetAddress.getByName("https://www.google.com");
if (!ipAddr.isReachable(10000)) {
return false;
} else {
return true;
}
} catch (Exception e) {
Log.e("exception", e.toString());
return false;
}
}
}
Is this code correct? Because I don't know how to call it. I tried:
new CheckConnectionTask().execute();
Is anything missing there? Because it doesn't work. Also please note that I've seen a lot of previous questions, but I didn't find any answer to this problem, so I asked my own question. If you've seen an answered question that can solve my problem you can link it here, but keep in mind that I am not experienced with Android or Java, so it might be unclear to me. I would preffer correct code as an answer, and a brief explaination why my didn't work. Also, I need to know if the phone is connected to the INTERNET, not a NETWORK, so ConnectivityManager won't wor for me.
EDIT - thank you all for your answers. First of all, I have all the permissions required. Also, I can't get any results currently, as Android Studio highlights the following code:
Boolean internetConnection;
internetConnection = new CheckConnectionTask().execute();
As incorrect and it simply won't let me call the function. What is wrong with it? Is it missing any parameters? Because I've defined params as Void so that seems illogical.
Edit 2 - I've used onPostExecute, as suggested by #vandaics, and it looks like this now:
private class CheckConnectionTask extends AsyncTask<Void, Void, Boolean> {
#Override
protected Boolean doInBackground(Void... params) {
try {
InetAddress ipAddr = InetAddress.getByName("google.com");
if (!ipAddr.isReachable(10000)) {
return false;
} else {
return true;
}
} catch (Exception e) {
Log.e("exception", e.toString());
return false;
}
}
#Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
internetConnection = result;
}
}
It works, and I call it when calling the onCreate method:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new CheckConnectionTask().execute();
}
It works, my apps checks if the Internet is connected and reacts properly. If you think something might not work, or there is an easier way to do that, let me know. Many thanks to you guys, especially #vandaics and #Sunil. Also, do I need to use superclass like here?:
#Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
internetConnection = result;
}
What does it do and is it necessary?
You currently are not seeing anything because you have no log statements or you are not really checking for anything.
The call
new CheckConnectionTask().execute()
is running the AsyncTask. It's just that there is no output for the task to show.
you can check for the output and see if it is what you want.
private class CheckConnectionTask extends AsyncTask<Void, Void, Boolean> {
#Override
protected Boolean doInBackground(Void... params) {
try {
InetAddress ipAddr = InetAddress.getByName("https://www.google.com");
if (!ipAddr.isReachable(10000)) {
return false;
} else {
return true;
}
} catch (Exception e) {
Log.e("exception", e.toString());
return false;
}
}
#Override
public void onPostexecute(Boolean result) {
// TO DO on the UI thread
Log.i("AsyncTask", "Result = " + result");
}
}
EDIT: The call:
new CheckConnectionTask().execute()
returns an instance of the AsyncTask that it is executing and not a Boolean (although you do specify that Boolean should be the output). Hence you are seeing a compilation error here. AsyncTask was designed to be self contained - it does everything it's supposed to do and then terminates. If you do have to modify a class level instance variable (from the class that contains the AsyncTask as an inner task) that can be done but not suggested.
to check if the internet connection is available, you can do this:
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null && activeNetworkInfo.isConnectedOrConnecting();
//return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}
You can't call
Boolean internetConnection;
internetConnection = new CheckConnectionTask().execute();
the return value of excute() is not what you want. If you want use asyntask you can set a boolean variable in onPostExecute(...) :
private boolean isConnect = false;
private class CheckConnectionTask extends AsyncTask<Void, Void, Boolean> {
#Override
protected Boolean doInBackground(Void... params) {
try {
InetAddress ipAddr = InetAddress.getByName("https://www.google.com");
if (!ipAddr.isReachable(10000)) {
return false;
} else {
return true;
}
} catch (Exception e) {
Log.e("exception", e.toString());
return false;
}
}
#Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(aVoid);
isConnect = result;
}
}
But, I never use this approach to get status of internet connection, beacause I must run this asyntask before everything to get exact status.
If you are going to use AsyncTaks you're missing the onPostExecute method:
protected void onPostExecute(Boolean result) {
//your code here
}
You can also add the optional onProgressUpdate method:
protected void onProgressUpdate(Integer... progress) {
//do something on update
}
Then to execute you do:
new DownloadFilesTask().execute();
Here is a good example you can use: http://developer.android.com/reference/android/os/AsyncTask.html
I'm writing an app for android in Java, and the server side also with Java.
The connection is through sockets. To send strings to the server I'm using asyncTask as follows:
public static void send(String content) throws IOException {
mConnectionHandler.new AsyncSendToServer().execute(content);
}
private class AsyncSendToServer extends AsyncTask<String, Void, Void> {
#Override
protected Void doInBackground(String... params) {
out.println(params[0]);
return null;
}
}
Now the response from the server is done as follows:
public static String receive() {
mConnectionHandler.new AsyncReceiveFromServer().execute();
return serverResponse;
}
private class AsyncReceiveFromServer extends AsyncTask<Void, Void, String> {
#Override
protected String doInBackground(Void... params) {
String result = null;
try {
result = in.readLine();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
protected void onPostExecute(String result) {
serverResponse = result;
}
}
Because the methods are async, the serverResponse does not get the appropriate value in receive(). When I execute AsyncReceiveFromServer, receive() return the value of serverResponse before it's get updated in the asyncTask. What can I do in order to send the updated serverResponse?
Execute your AsyncReceiveFromServer from the onPostExecute of your AsyncSendToServer.
This way, you are absolutely certain that the Send has finished.