Im using a web service, so I want to use an async thread for the HTTP authentication request and another thread later to make additional service requests while my main thread runs.
Would like to see a good example of how to do this and how to show busy messages somehow in main app. How does the main app know when the thread finished? And what if my thread encounters exceptions, how do I deal with that?
HTTP requests are sent later, use the same cookies setup up by the first auth request, so will the later requests pick up the same cookies and just work?
Even better look here for the async part: Is there an accepted best-practice on making asynchronous HTTP requests in Android?
Look at here How to execute web request in its own thread?
AndroidAsync library I wrote to handle this automatically, it will run in the background and reinvoke onto the UI thread:
https://github.com/koush/AndroidAsync
// url is the URL to download. The callback will be invoked on the UI thread
// once the download is complete.
AsyncHttpClient.getDefaultInstance().get(url, new AsyncHttpClient.StringCallback() {
// Callback is invoked with any exceptions/errors, and the result, if available.
#Override
public void onCompleted(Exception e, String result) {
if (e != null) {
e.printStackTrace();
return;
}
System.out.println("I got a string: " + result);
}
});
Related
I made a app the connects to a ble device and receives data from it. I was following this link "http://toastdroid.com/2014/09/22/android-bluetooth-low-energy-tutorial" at the Hints and observation section it says to Queue All GATT operations. How do I do that?
Check out NordicSemiconductors open source project Puck Central, or more specifically the GattManager class, who perfectly demonstrates how to queue all GATT operations.
If you don't want to handle this sort low level bluetooth specifics yourself however, I can recommend the great library RxAndroidBle, which does much of the heavy lifting for you.
To queue the requests you could make a queue class which has an Arraylist of requests.
Every time you want to make a request add it to the queue and start processing the queue (if the queue isn't already being processed). Once you've processed the current item check if there are still items to process and carry on processing them.
You'll also probably need to add a timeout in case one of the requests gets stuck.
Sample code on how you could process a queue using a handler:
private void startProcessingQueue() {
if (queueIsRunning) {
return;
}
queueIsRunning = true;
h.postDelayed(new Runnable(){
public void run(){
processQueue();
if(queue.isEmpty()) {
queueIsRunning = false;
return;
}
h.postDelayed(this, QUEUE_PROCESSING_DELAY);
}
}, QUEUE_PROCESSING_DELAY);
}
I have an Android application that uses AsyncTasks to make get and post calls to send and retrieve data from server. All works fine but sometimes the async task takes a lot of time to execute and thus other async tasks have to wait (if more than 5 async tasks is there) so what will be the best alternative or how to increase the thread pool if it is safe to do so.
Asynctask are implemented behind the scene using threadpool, the default pool size for asynctasks is 1(so you can't run 2 asynctasks in parallel).
In newer versions of android the default Asynctask pool size is 5.
It's possible to change it but not recommended.
You can just create thread like in the sample I attached before:
Thread thread = new Thread() {
#Override
public void run() {
try {
//Do http request here
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
thread.start();
I'm trying to handle the situation where the user loses their data connection during an Http request in an AsyncTask. Currently the AsyncTask will never finish executing if this happens and the app just stalls. I can't even check isCancelled() because the Http request just stalls out on one function call, so I can't implement a loop or anything.
I'm using the following in the UI thread but I can't figure out how to check if the task has been cancelled from within the task:
task = new LoginTask();
task.execute(this, mUsername, mPassword);
Handler handler = new Handler();
handler.postDelayed(new Runnable()
{
#Override
public void run()
{
if (task != null && task.getStatus() == AsyncTask.Status.RUNNING)
{
task.cancel(true);
}
}
}, 5000);
Since KSoap 2 is written in Java, an option for you would be to abstract one of the classes and manually set a timeout on the HttpConnection.
Based on our prior discussion, you will probably have to override the method that doesn't set a timeout on the connection and replace it with your own method and a connection that times out. Should be managable thanks to KSoap being open source! Good luck.
In order to stop processing, you would need to do a check on isCancelled() inside doInBackground(). If there are any reasonable places to do so in your doInBackground, you can add an if-statement. Otherwise you should consider setting a timeout on the http connection.
I'm kinda new to android development, but i'm trying to make a xml parser. I've been using android.sax library, following some tutos, and this works great.
One thing that is making me sceptical, is that I don't actually launch the parser in a separate thread, I just use a handlers to communicate between my parser and my main activity.
Should I parse in a Thread ?
Here's my main activity code :
tv = (TextView)findViewById(R.id.tv);
try {
URL url = new URL("https://www.googleapis.com/shopping/search/v1/public/products?key=AAAAABBBBBCCCCDDDEEEEFFF&country=FR&restrictBy=gtin=5030999075254&alt=atom");
XMLHandler xHandler = new XMLHandler();
Feed feed = xHandler.parse(url.openStream());
if(feed.getTotalResults()==0 || feed.getItems() == null || feed.getItems().isEmpty()) {
Log.w("XMLPARSENull", "No items
}
else {
tv.setText(feed.getTotalResults()+" " + feed.getItemsPerPage() + " " + feed.getStartIndex() + " " + feed.getTitle());
Iterator<Product> it = feed.getItems().iterator();
while(it.hasNext()) {
Log.w("XMLPARSEFeed",it.next().getName());
}
}
} catch(Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e("XMLPARSEException", "ERROR",e);
}
I don't think that it's the parsing so much as the network operation, as any network request should not be performed in the UI thread. You can either spawn a new Thread or an AsyncTask to perform your network request. Here are some links to help:
AsyncTask
Painless threading
Expensive operations
Designing for responsiveness
Thread documentation
Handler documentation
A simple answer:
If you have connections in your main ( UI ) thread, the user interface will become frozen whilst the thread is used to download the information and parse it. It takes some time for a connection so it may appear to freeze.
Apart from that, android 4.0 now does not actually allow you to call HTTP requests from this thread, it will throw an error which will be seen in logcat before crashing.
It is best practise to use an Async Task here, here is some more information on that.
Information on Async Tasks!
Yes, it is imperative that you move your parsing into a background thread, particularly if your XML is being streamed across the network; otherwise your app is likely to be killed off by the system for blocking the main thread.
You don't have to use a raw Thread, though; Android provides things like ASyncTask to make it a bit easier.
Everything which isn't related to direct interaction with GUI should be moved to separate thread, prefferably AsyncTask if you need interaction with GUI from that thread since Android won't allow accessing GUI from regular Thread class.
http://developer.android.com/reference/android/os/AsyncTask.html
In my app i connect to a server, which responds with an xml. I parse it with the SAX Parser, and get the data.
The question is:
What is the best way to handle connection issues?
(At this moment if there is no internet connection available the app simply continues showing the ProgressDialog i implemented)
So you basically do (Pseudo code)
ProgessDialog pd = new ProgressDialog(this).show();
Sax.parseStuff();
pd.dismiss();
In this case, wrap the parsing stuff and cancel the dialog on Exception
ProgessDialog pd = new ProgressDialog(this).show();
try {
Sax.parseStuff();
}
finally {
pd.dismiss(); // or cancel
}
You can also do a try { .. } catch (XYZException e ; pd.cancel(); throw e) if you want to process the Exception in a different layer of your app.
As well as following the suggestion of Heiko Rupp, you can also check for the availability of a network connection prior to performing your download. See my post on the subject.