Async PostExecute

Question

I have been able to set up a connection between my socket server (running on ruby) and my client, which is an Android(java) application. I will explain what my goal is.

I have to send a string to my server through the socket. Depending on the contents of the string, the server would execute a process in the database (store, delete, view data, etc).

The first option is to validate the user name/password. Im able to send the correct string, and the server receives it and replies back to me with the correct response (after validating whether or not my username is capable of logging into the application). Now, depending on this response i need to change the current activity (loginActivity) with the next activity (MenuActivity) so that the user can proceed to use the application menu.

Since the socket has to run on a different thread other than the UIThread, im running it using the AsyncTask way. However im having problems triggering the activity change thing after the AsyncTask process is over.

What im doing is, after the whole Async task is done (onPostExecute method) im trying to call up the activity, but its not working. This is what i've tried (based on similar cases i've found during research):

(AsyncTask class)

Context context;
private void AppContext(Context context) {
    this.context = context.getApplicationContext();
}

OnPostExecute

Intent NewActivity = new Intent();
NewActivity.setClass(context.getApplicationContext(),MainActivity.class);
context.startActivity(NewActivity);

However this is not working and its causing my app to crash with a "thread exciting with uncaught exception"

I've tried showing only a Toast message that says "Granted" or "Denied" just to test it with a simpler task, but i keep getting the same error so im assuming its got to do with handling the change between the thread on which the Async task is running and the UI thread. Any ideas?

P.S: I've checked the other questions that are similar to mine and tried the suggested code, but nothing's worked.

ERROR LOG

09-29 09:59:11.387: E/AndroidRuntime(2856): FATAL EXCEPTION: main
09-29 09:59:11.387: E/AndroidRuntime(2856): java.lang.NullPointerException
09-29 09:59:11.387: E/AndroidRuntime(2856):     at com.example.prescoterm.SocketClass.onPostExecute(SocketClass.java:111)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at com.example.prescoterm.SocketClass.onPostExecute(SocketClass.java:1)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at android.os.AsyncTask.finish(AsyncTask.java:602)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at android.os.AsyncTask.access$600(AsyncTask.java:156)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at android.os.Looper.loop(Looper.java:137)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at android.app.ActivityThread.main(ActivityThread.java:4424)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at java.lang.reflect.Method.invokeNative(Native Method)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at java.lang.reflect.Method.invoke(Method.java:511)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-29 09:59:11.387: E/AndroidRuntime(2856):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

Ok so i found a workaround this, now i would like to hear from you guys if you think this'd be a suitable solution.

Since the problem was that the context was coming up null at my AsyncTask class, i decided to load the value on a variable from the moment the application start.

context = this.getApplicationContext(); 
new SocketReception().setContext(context);

On my SocketReception Class i had a setContext(context) method.

public void setContext(Context context) 
    {
        SocketReception.appContext= context;
    };

Now, on my AsyncTask post.execute i call the new activity like this:

SocketReception.appContext.startActivity(NewActivity);

Its now working, but i want to know if this is a convenient approach or if i should keep looking for a different solution.

P.S: I had to add the unpopular "FLAG_ACTIVITY_NEW_TASK", will research on how to avoid this later on.

Answer 2

I have used this asynctask directly in activity and work fine, may be help. When i try call Intent i = new Intent(getApplicationContext(), VyberIcoActivitySD.class); in class without context ( class extended not Activity, Fragment... ) i have not result...

class SynchroAllIcosSD extends AsyncTask<String, String, String> {


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(SynchroIcoActivitySD.this);
        pDialog.setMessage(getString(R.string.progdata));
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }


    protected String doInBackground(String... args) {

    //do something

        return null;
    }


    protected void onPostExecute(String file_url) {
        // dismiss the dialog after getting all products
        pDialog.dismiss();
        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {


                Intent i = new Intent(getApplicationContext(), VyberIcoActivitySD.class);
                Bundle extras = new Bundle();
                extras.putString("odkade", "100");
                extras.putString("page", "1");
                i.putExtras(extras);
                startActivity(i);
                finish();

            }
        });

    }

}