Question

Hi I’m making Login page that access MySQL database. But my Activity always runs the code that check fail/success before it finishes the AsyncTask.

I tried using asynctask.get() method, but it just freeze my UI and doesn’t work.

I tried this answer that said I should call the result-checker method inside onPostExecute().

But since I need to change the TextView to show success/failed, it results in NullPointerException because I instantiate the TextView inside onCreate().

I can’t move the TextView instantiation into constructor because it will return NullPointerException unable to instantiate activity ComponentInfo.

Login.java

public class Login extends Activity{

    //declare global Views here

    protected void onCreate(Bundle bundle){
        //Setup views
    }

    protected void onClick(View v){
        //Setup necessary variables
        AsyncClass async = new AsyncClass(this);
        async.execute(username, password);
    }

    public void checkSuccess(boolean success){
        if(success)
            textView1.setText("Success");
        else
            textView1.setText("Failed");
    }
}

AsyncClass.java

public class AsyncClass extends AsyncTask<String, String, JSONObject>{
    protected JSONObject doInBackground(String... params){
        //access database
    }

    protected void onPostExecute(JSONObject json){
        //read the json result
        Login login = new Login();
        login.checkSuccess(true);
    }
}

Any solution? Thanks

Answer 1

try this

protected void onPostExecute(JSONObject json){
    //read the json result
    Login login = (Login)context; // object that you pass to task constructor
    login.checkSuccess(true);
}

Also you can add progress dialog to your task to indicate some job execution

public class BaseTask<T> extends AsyncTask<Object, Void, T> {

public Context context;
public ProgressDialog dialog;

public BaseTask(Context context) {
    this.context = context;
    this.dialog = new ProgressDialog(context);
}

@Override
protected void onPreExecute() {
    this.dialog.setMessage(context.getResources().getString(R.string.loading));
    this.dialog.show();

}

@Override
protected T doInBackground(Object... objects) {
    //....
    return something;
}

@Override
protected void onPostExecute(T result) {
    if (dialog != null && dialog.isShowing())
        dialog.dismiss();
    // do something
}

}