public static variable has the value , but when i try to show it to textview(in another class) it has no value

Question

my activity flow , Login page->mainpage(in this i have a button to go to Userprofile which has a onclick method)-> button onclick method is "startactivity(Userprofile)" I have a onClick method which loads the activity Userprofile. I want to load the details of the user, i have some static variables but no luck.

public class Userprofile extends AppCompatActivity {
    TextView textView , textView1 , textView2 ;
    Context context_userprofile;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_userprofile);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        func_userprofile_show();
    }

    public void func_userprofile_show(){
        String type = "linkuser";
        DatabaseLink databaseLink = new DatabaseLink(this);
        databaseLink.execute(type);
        context_userprofile = getApplicationContext();
        textView = (TextView)findViewById(R.id.tvprofilepage_user);
        assert textView != null;
        textView.setText(DatabaseLink.thename);
        textView1 = (TextView)findViewById(R.id.tvprofilepage_ign);
        assert textView1 != null;
        textView1.setText(DatabaseLink.theign);
        textView2 = (TextView)findViewById(R.id.tvprofilepage_emailid);
        assert textView2 != null;
        textView2.setText(DatabaseLink.theemail);
    }
}

Now this is a method from diffrent class which extends AsyncTask and "theign" is showing in AlertDialog but not in TextView.

public void decodejson() {
    try {
        JSONObject jsonObj = new JSONObject(myJSON);
        details_json = jsonObj.getJSONArray(TAG_RESULTS);

        for (int i = 0; i < details_json.length(); i++) {
            JSONObject c = details_json.getJSONObject(i);
            thename = c.getString(TAG_NAME);
            theign= c.getString(TAG_IGN);
            theemail = c.getString(TAG_EMAIL);
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

@Override
protected void onPreExecute() {
    alertDialog = new AlertDialog.Builder(context).create();
    alertDialog.setTitle("User Profile Loading...");
}

@Override
protected void onPostExecute(String result) {
    myJSON = result;
    decodejson();
    alertDialog.setMessage(theign);
    alertDialog.show();
}

use interface as a callback to the activity and update your views there — Raghunandan, Jul 11 '16 at 11:00
I think theign is still null in Userprofile because the value will be filled when the AsyncTask completes. As @Raghunandan said keep a callback when task finishes then set the theign to textView. — Raghavendra, Jul 11 '16 at 11:04
Launch your `Activity` in the post execute when the values are populated properly. — Reaz Murshed, Jul 11 '16 at 11:05
@Raghunandan how to use interface as a callback , please explain — Hemant Vyas, Jul 11 '16 at 11:15
@HemantVyas example @ http://stackoverflow.com/questions/16752073/how-do-i-return-a-boolean-from-asynctask — Raghunandan, Jul 11 '16 at 11:18
decodejson() is inside DatabaseLink? put the code and I could give you an example — adalpari, Jul 11 '16 at 11:24
@adalPaRi yes decodejson() is inside DatabaseLink( extends asynctask) — Hemant Vyas, Jul 11 '16 at 11:32
@adalPaRi my activity flow , Login page->mainpage(in this i have a button to go to Userprofile which has a onclick method)-> button onclick method is "startactivity(Userprofile)" now code of userporifle is above. — Hemant Vyas, Jul 11 '16 at 11:35

adalpari · Accepted Answer · 2016-07-11T14:57:33.173

The problem is that textView.setText is called before AsyncTask has finished.

To solve the problem you can implement an interface for call the function inside the activity when the info is ready. Assuming the AsynkTask is inside your DatabaseLink class, I will sow you some pseudocode..

Interface:

public interface DatabaseLinkInterface {
    public void databaseLinkFinished();
}

The context will be also the listener. You have the context in your DatabaseLink class:

@Override
protected void onPostExecute(String result) {
    myJSON = result;
    decodejson();
    alertDialog.setMessage(theign);
    alertDialog.show();
    DatabaseLinkInterface mListener = (DatabaseLinkInterface) context;
    mListener.databaseLinkFinished();
}

Implement the interface in your activity and create DatabaseLink in onCreate:

public class Userprofile extends AppCompatActivity implements DatabaseLinkInterface {
    TextView textView , textView1 , textView2 ;
    Context context_userprofile;
    DatabaseLink databaseLink;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_userprofile);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        String type = "linkuser";
        databaseLink = new DatabaseLink(this);
        databaseLink.execute(type);
    }

    ...

And finally, in your activity, implements the interface method to know when the data is fetched. Remove func_userprofile_show(). Avoid to use static variables for this purpose.

@Override 
public void databaseLinkFinished(){
    context_userprofile = getApplicationContext();
    textView = (TextView)findViewById(R.id.tvprofilepage_user);
    assert textView != null;
    textView.setText(databaseLink.thename);
    textView1 = (TextView)findViewById(R.id.tvprofilepage_ign);
    assert textView1 != null;
    textView1.setText(databaseLink.theign);
    textView2 = (TextView)findViewById(R.id.tvprofilepage_emailid);
    assert textView2 != null;
    textView2.setText(databaseLink.theemail);
}

I also recommend you to use getters and setters instead of access directly to the attribute (databaseLink.theemail -> databaseLink.getTheEmail())

I need to write the interference in Userprofile(activity) ? and mlistener = context , mlistener is not a context type — Hemant Vyas, Jul 11 '16 at 12:11
what should be in databaselinkFinished() , when and from where we need to call populateData() ? .... sry but i am in learning phase :P . — Hemant Vyas, Jul 11 '16 at 12:18
I've fix one mistake, populateData() is actually databaselinkFinished(). Then, mListener = context because you implement DatabaseLinkInterface inside Userprofile Activity. So when the AsyncTask is finissed you will call the activity.databaselinkFinished(), telling thet the object is filled. — adalpari, Jul 11 '16 at 13:41
Ok but how mListener = context ? , mListener is not a Context variable right ? , DatabaseLinkInterface mListener = context gives error. — Hemant Vyas, Jul 11 '16 at 14:49
That's true but in this case context is Userprofile Activity and Userprofile Activity is DatabaseLinkInterface, aren't they?. So this context can be casted to DatabaseLinkInterface (mListener). — adalpari, Jul 11 '16 at 14:52
DatabaseLinkInterface mListener = (DatabaseLinkInterface)context; right ? — Hemant Vyas, Jul 11 '16 at 14:53
yeah thanks man it worked! :D Now i will work for showing users online xD — Hemant Vyas, Jul 11 '16 at 17:13
i got to retrieve some values from mysql table , my php side is done but not in android side i have the same problem as above , what should i do ? data from mysql database is not constant it depends on some query , like it can come 5 diffrent values or 10 , its not constant. — Hemant Vyas, Jul 18 '16 at 08:29

public static variable has the value , but when i try to show it to textview(in another class) it has no value

1 Answers1